Legal Standards and Procedures

Whether scientific evidence is admissible in criminal cases depends on whether the evidence tends to prove or disprove a fact that, under the applicable law, might matter to the outcome of the case; whether the expert presenting the evidence is qualified; whether the information is derived from scientifically acceptable procedures; and whether the potential for unfair prejudice or time-consumption substantially outweighs the probative value of the information. We discuss those general principles and then consider their application to DNA evidence. We also describe pretrial and trial procedures that might help courts to reach decisions on admissibility and to improve the quality and use of the scientific evidence at trial. We begin with the intertwined procedural issues that arise in connection with a defendant's request for discovery, retesting, or expert assistance.

Typing Methods

Laboratory Error

Defendants have challenged the admissibility of DNA results on the grounds that the protocols or procedures followed by the laboratory were inadequate to reduce the risk of error sufficiently, that the laboratory failed to adhere to the stated protocols, or that the laboratory failed to demonstrate its ability to type samples accurately on a series of external, blind proficiency tests. Courts have shown little inclination to exclude evidence on those grounds.⁴⁰ Although egregious departures from customary practices might well lead a court to exclude the evidence, the possibility of laboratory error ordinarily is said to affect the weight rather than the admissibility of the evidence, e.g., Hopkins v State, 579 N.E. 2d 1297 (Ind. 1991) (departures from protocol). At the same time, some courts, expressing concern over the impact of DNA evidence on jurors, have grafted a procedural safeguard onto the general-acceptance standard. Starting with People v Castro, 144 Misc. 2d 956, 545 N.Y.S. 2d 985 (Sup. Ct. 1989), a minority of courts have treated an inquiry into a laboratory's conforming in a particular case to a generally accepted protocol as an essential part of a pretrial hearing under Frye.⁴¹

We emphasized the importance of minimizing laboratory error in Chapter 3, where we called for scrupulous care in sample-handling and laboratory procedures, for regular participation in proficiency tests, and, whenever feasible, for procedures that would offer defendants the opportunity for a second test by an independent laboratory. Those recommendations rest not on a judgment that current error rates are so high that test results are scientifically unacceptable, but on a desire to reduce the incidence of errors to an extremely low value.

It is possible that courts will want to treat compliance with such recommendations as an aspect of admissibility to encourage laboratories to follow them.⁴² That result is not compelled by Daubert or Frye, but in some jurisdictions a defendant does have the right to examine physical evidence held by the government, and this right has been construed to include the right to test or retest a sample in the government's control.⁴³

A number of issues can arise even when the right to a second test is recognized. Does the prosecution have a right to be present?⁴⁴ When is the defendant's request timely? How specific a request must the defendant make?⁴⁵ Does retesting by another laboratory suffice, or must the testing be done under defense supervision?⁴⁶ Does it matter whether the laboratory is a government, rather than an independent nongovernment, laboratory?⁴⁷ Will the state pay if the defendant is indigent?

Of course, the right of indigent defendants to expert assistance at state expense extends beyond the right to retest. In some circumstances, the constitution requires that indigent defendants be provided with funds to retain suitable experts. The leading case is Ake v Oklahoma, 470 U.S. 68 (1985). In Ake, the Supreme Court reversed a conviction because the trial court had refused to appoint an expert to assist the indigent defendant, who was relying on an insanity defense. But Ake was a capital case in which the defense sought the assistance of a psychiatrist, and courts have differed in their interpretation of the holding (Harris 1992). Some courts have applied Ake broadly to authorize all types of expertise; others have restricted Ake to its particular facts, focusing on the type of assistance requested and on whether the prosecution was seeking the death penalty (see Harrison v State, 644 N.E.2d 1243 [Ind. 1995]). Furthermore, courts differ in how much of a particularized showing of need and potential prejudice a defendant must make.⁴⁸ Those variations in the interpretation of Ake have produced conflicting results when indigent defendants have sought expert assistance with regard to DNA testing. Some courts have held that an expert must be provided, ⁴⁹ and others have found no such need.⁵⁰

Instead of providing a defendant with an expert, a court might appoint an expert to assist the court. As noted in the earlier discussion of expert witnesses, courts have been more inclined to use this procedure to investigate general scientific issues related to DNA profiling than to resolve controversies related to the particulars of the DNA testing in a given case. However, no rule of law clearly compels such a limitation on court-appointed experts.

Returning to the implications of recognizing a defendant's right to retesting whenever feasible, difficult issues can arise as to informing the jury of the defense's failure to retest or of the results of any retesting. May the prosecution comment on or introduce evidence about the defendant's failure to request retesting or to introduce DNA-testing results?⁵¹ May it cross-examine defense experts about a failure to retest?⁵² May it obtain discovery or testimony from an expert who conducted retesting for the defense but whom the defense does not intend to call as a witness?⁵³ The law with regard to those questions is far from clear.⁵⁴ Implicated are state and federal constitutional concerns emanating from due process⁵⁵ and effective-assistance-to-counsel provisions,⁵⁶ such evidentiary doctrines as the attorney-client⁵⁷ and work-product privileges,⁵⁸ and criminal-procedure issues related to discovery.⁵⁹

Beyond all that, the recommendation to give a defendant the opportunity to retest whenever possible leaves open the question of how to proceed when a sample is too small to permit splitting. Some opinions suggest that if the prosecution consumes the evidence in the course of testing, it will not be constitutionally barred from introducing the results as long as it acted in good faith.⁶⁰ The Supreme Court has held that even a negligent failure to preserve evidence does not offend due process.⁶¹ However, as one commentator notes, a "situation in which lost evidence might be exculpatory differs from one in which inculpatory evidence will be offered. A higher duty of care should be required in the latter situation" (Giannelli 1991, p 820).

One possible response to the problem of testing that legitimately consumes the sample is to give the defendant the right to have an expert present if prosecution testing will consume the available sample. E.g., State v Gaddis, 530 S.W.2d 64, 69 (Tenn, 1975). However, additional steps might have to be taken to make this right meaningful. ⁶² When later independent testing is not possible and the defendant is not provided an opportunity to have an independent expert observe the testing, or the testing is performed before charges are filed, our recommendation that all stages of the testing process be fully documented becomes particularly important.⁶³ In such cases, experts who report to the defense or directly to the court might be helpful in verifying that there are no ambiguities in the autoradiographs or that any ambiguities are properly accounted for.

Whereas our recommendations are directed at reducing the chance of error and detecting errors that do occur in rare cases, defendants and some legal commentators have contended that the risk of laboratory or handling errors that would falsely incriminate a suspect should be estimated from external, blind proficiency tests, and a few courts have held that a laboratory's record in proficiency tests must accompany its estimate of the probability of a matching profile. E.g., United States v Porter, 1994 WL 742297 (DC Super. Ct., Nov. 17, 1994). We believe that proficiency-testing is a valuable device for reducing errors of all kinds, should be implemented as a matter of social policy, and bears on the weight that should be accorded forensic test results. At the same time, for the reasons given in Chapter 3, we have concluded that it is exceedingly difficult to estimate relevant error rates from either industry-wide or laboratory-specific proficiency-test results.

A question arises as to the admissibility of proficiency-test statistics themselves. The 1992 NRC report stated that the probative value of such statistics, when balanced against their potential to mislead a jury, favored admissibility: ''laboratory error rates must be continually estimated in blind proficiency testing and must be disclosed to juries" (p 89). Inasmuch as the purpose of our report is to determine what aspects of the procedures used in connection with forensic DNA testing are scientifically valid, we attempt no such policy judgment.

Explaining the Meaning of a Match

Once two samples are found to have similar profiles, the question arises as to what, if anything, the trier of fact may be told about the significance of this finding. Before forensic experts can conclude that DNA testing has the power to help identify the source of an evidence sample, it must be shown that the DNA characteristics vary among people. Therefore, it would not be scientifically justifiable to speak of a match as proof of identify in the absence of underlying data that permit some reasonable estimate of how rare the matching characteristics actually are.

However, determining whether quantitative estimates should be presented to a jury is a different issue. Once science has established that a methodology has some individualizing power, the legal system must determine whether and how best to import that technology into the trial process (Kaye 1995, p 104-105). If the results are sufficiently probative to be admissible, the conceivable alternatives for presentation range from statements of the posterior probability that the defendant is the source of the evidence DNA (see Chapter 5), to qualitative characterizations of this probability, to computations of the likelihood ratio for the hypothesis that the defendant is the source, to qualitative statements of this measure of the strength of the evidence, to the currently dominant estimates of profile frequencies or random-match probabilities, to unadorned reports of a match.

Few courts, if any, have examined the full range of alternatives, and courts have reached conflicting conclusions as to the acceptability of those modes of presentation that they have examined. Here, we outline the alternatives, identify the considerations that affect their suitability, and discuss the social science research that supplies some information on the possible effects of the various types of presentations on the jury.

Conclusions

This chapter has described some of the legal principles and procedures governing the admission and use of DNA evidence in the courtroom and how this evidence has been received over the last decade. In assimilating scientific developments, the legal system necessarily lags behind the scientific world. Before making use of evidence derived from scientific advances, courts must scrutinize the proposed testimony to determine its suitability for use at trial, and controversy within the scientific community often is regarded as grounds for the exclusion of the scientific evidence. Although some controversies that have come to closure in the scientific literature continue to limit the presentation of DNA evidence in some jurisdictions, courts are making more use of the ongoing research into the population genetics of DNA profiles. We hope that our review of the research will contribute to this process.

In this chapter, we have also discussed how our conclusions and recommendations for reducing the risk of laboratory error, for applying human population genetics to DNA profiles, and for handling uncertainties in estimates of profile frequencies and match probabilities might affect the application of the rules for the discovery and admission of evidence in court. Many suggestions can be offered to make our recommendations most effective: for example, that every jurisdiction should make it possible for all defendants to have broad discovery and independent experts; that accreditation, proficiency-testing, and the opportunity for independent testing (whenever feasible) should be prerequisites to the admission of laboratory findings; that in resolving disputes over the adequacy or interpretation of DNA tests, the power of the court to appoint its own experts should be exercised more frequently; and that experts should not be barred from presenting any scientifically acceptable estimate of a random-match probability. We have chosen, however, to make no formal recommendations on such matters of legal policy; the single recommendation in the chapter concerns scientific evidence—namely, the need for behavioral research that will assist legal decision makers in developing standards for communicating about DNA in the courtroom:

Recommendation 6.1: Behavioral research should be carried out to identify any conditions that might cause a trier of fact to misinterpret evidence on DNA profiling and to assess how well various ways of presenting expert testimony on DNA can reduce such misunderstandings.

We trust that our efforts to explain the state of the forensic science and some of the social science findings that are pertinent to resolving these issues will contribute to better-informed judgments by courts and legislatures.

Appendix 6A

The following tables summarize the law in the United States on the admissibility of estimates of profile frequencies or random-match probabilities of DNA types. Table 6.1 lists the leading cases or statutes in each jurisdiction with a parenthetical explanation of the result in each case. Table 6.2 presents this information in a more abbreviated format. In many of the more recent cases, both an interim-ceiling and product-rule estimates were presented. The tables do not show whether an opinion holds or suggests that the product-rule estimate would have been inadmissible had the ceiling estimate not been included. Many other subtleties and issues that arise in these cases are not captured in this brief summary.

TABLE 6.1

Leading Cases and Statutes on Admissibility of Inclusionary DNA Evidence by Jurisdiction, as of June 1995.

TABLE 6.2

Admissibility of Inclusionary DNA Evidence by Jurisdiction, as of June 1995.

Footnotes

1

Unless otherwise indicated, our observations apply to all the technologies for DNA analysis described in this report.

2

State v Bogan, 905 P.2d 515, 522-23 (Ariz. Ct. App. 1995), rev. granted.

3

State v Bogan, 905 P.2d 515, 522-23 (Ariz. Ct. App. 1995), (dissenting opinion challenging the majority's conclusion that the "'tenuous distinction between molecular genetics and other scientific disciplines' should [not] cause DNA opinion evidence to be treated differently from other opinion testimony that is customarily allowed to support other kinds of scientific evidence") rev. granted; Neufeld and Colman (1990) (advocating more rigorous standards for forensic science generally); Saks and Koehler (1991) (calling for more rigorous validation of many forensic tests).

4

State v Schwartz, 447 N.W.2d 422, 427 (Minn. 1989) ("access to the data, methodology, and actual results is crucial so a defendant has at least an opportunity for independent expert review").

5

See, e.g., United States v Yee, 129 F.R.D. 629 (N.D. Ohio 1990) (even before 1993 amendment to Federal Rule of Criminal Procedure 16(a)(1)(E), a federal magistrate judge granted discovery of matching criteria, environmental insult studies, population data, and proficiency tests as "predicate materials" essential to the defense in a DNA-testing case); State v Schwartz, 447 N.W.2d 422, 427-28 (Minn. 1989) (although a laboratory disclosed its protocol, laboratory notes, autoradiographs, and frequency tables, its refusal to supply "more specific information on its methodology and population data base" was a reason to exclude the findings); People v Davis, 196 A.D.2d 597, 601 N.Y.S.2d 174 (Sup. Ct. 1993) (Lifecodes was required on constitutional grounds to turn over statistical data underlying a DNA probability estimate); cf. State v Feldman, 604 A.2d 242, 244 (N.J. Super. 1992) (defense was entitled to discovery related to a databank search of the Automated Fingerprint Information Service). A few statutes governing the admissibility of DNA tests include provisions for pretrial discovery of the state's report. E.g., 10 Md. Code Ann. Cts. & Jud. Proc. § 10-915(3)(b).

6

See, e.g., State v Dykes, 847 P.2d 1214, 1217-1218 (Kan. 1993) (request of a defendant claiming American Indian ancestry to obtain discovery of a data bank denied, but court permitted discovery of state laboratory's notes, autoradiographs and testing protocol); Spencer v Commonwealth, 384 S.E.2d 785, 791 (1989) (written laboratory reports discoverable, but rules expressly excluded discovery of expert's underlying "work notes [or] memorandum"), cert. denied, 110 U.S. 1171 (1990); cf. United States v Iglesias, 881 F.2d 1519, 1523 (9th Cir. 1989) (discovery of log notes, protocols, or other internal documents of chemists analyzing heroin was denied).

7

See, e.g., United States v Shue, 766 F.2d 1122, 1135 (7th Cir. 1985) (oral report of FBI photographic expert not discoverable pursuant to Federal Rule 16), cert. denied, 484 U.S. 956 (1987). Rule 16 was amended in 1993 to require that the government disclose to a defendant a summary of the expert testimony that the prosecution intends to offer on direct examination and the bases therefore. It is still unclear whether this provision will cause experts to provide more detailed written documentation than they previously furnished. Many states do not have a counterpart to this subdivision. Other jurisdictions make all discovery related to scientific tests discretionary, and still others explicitly provide for the discovery of oral reports of examinations or tests. See Giannelli and Imwinkelried (1993), vol. 1, § 3.2.

8

See generally McCormick 1992. § 203, p 875 n 40; Berger 1994, p 63; Kaye and Freedman 1994. p 337. In State v Carter, 246 Neb. 953, 524 N.W.2d 763 (1994), the Nebraska Supreme Court, in reversing a conviction involving a PCR DQA test on the grounds that the 1992 NRC report indicated lack of general acceptance of calculations that assumed Hardy-Weinberg proportions, noted the absence of testimony from a population geneticist. See also Swanson v State, 308 Ark. 28, 823 S.W. 812 (1992) (an argument that a serologist lacked a PhD and was not qualified as an expert in population genetics and therefore could not testify about probabilities was not preserved for appeal): Powell v State, 598 S.W.2d 829 (Tex. Ct. Crim. App. 1994) (argument that molecular biologist should not have been allowed to testify "concerning probabilities of matching DNA patterns because ... the witness had not been qualified as an expert in the field of population genetics" not made at trial, and therefore not preserved for appeal). Trial judges ordinarily are accorded great discretion in evaluating the qualifications of a proposed expert witness, and the decisions depend on the background of each witness. E.g., United States v Davis, 40 F. 3d 1069 (10th Cir. 1994) (the court rejected the argument that a witness "was not qualified to testify regarding population genetics" because ''acceptance of an expert's qualifications will be disturbed only for a clear abuse of discretion" and the witness "had thirteen years experience working for the FBI," "a Master's degree in cell biology," and "six months of specialized training in DNA profiling"): State v McFadden, 458 S.E. 2d 61 (S. Car. 1995) (there was no abuse of discretion in allowing a microbiologist employed by the state's forensic laboratory to testify as to the nature of databases and as to product-rule estimates of 1/(710 million) for blacks and 1/(1.7 billion) for whites); State v Lewis, 654 So. 2d 761 (La. Ct. App. 1995) (the court of appeals held that the trial court abused its discretion by denying expert status to a technician who presented herself as an expert in molecular biology and DNA analysis; the technician had been the assistant director of a laboratory for a year and had no doctoral degree, but belonged to invitational professional organizations, had received numerous academic awards, had testified as an expert in other cases, and had written 14 articles in collaboration with the laboratory director—in promotional rather than scientific publications).

9

E.g., State v Colbert, 257 Kan. 896, 869 P.2d 1089 (1995) (in view of general acceptance of VNTR databases, estimate of match probability admissible despite expert's concessions that he was not a population geneticist and was not qualified to explain how the databases applied to the town of Coffeyville).

10

In the federal courts, Federal Rule of Evidence 706 authorizes a court to appoint an expert. Many jurisdictions have similar rules. As with the appointment of defense experts, the federal courts have relied on the Criminal Justice Act § 06(A)(E).

11

Cecil and Willging (1994, p 542). In some cases, defendants have sought court-appointed experts to review the work of the state's experts. E.g., Taylor v Commonwealth, 1995 WL 808189 (Va. Ct. App. 1995) (unpublished opinion refers to corroboration "by an independent DNA expert appointed by the trial court on defendant's motion"). Other opinions refer to independent experts without indicating the manner of their appointment. E.g., Williams v State, 265 Ga. 351, 455 S.E. 2d 836 (1995) (observing that "an independent geneticist concurred with the DNA findings").

12

Statutes applicable to criminal cases include 11 Del. Code § 3515; Ind. Code § 37-4-13; 15 La. Stat. Ann. § 441.1; 10 Md. Code Ann. § 915; Minn. Stat. § 634.25; Tenn. Code Ann. § 24-7-117 (1993 Supp.); Va. Stat. § 19.2-270.5; NRC 1992, p 141-142. The Tennessee statute, for example, provides that "in any civil or criminal trial, hearing or proceeding, the results of DNA analysis ... are admissible in evidence without antecedent expert testimony that DNA analysis provides a trustworthy and reliable method of identifying characteristics in an individual's genetic material upon a showing that the offered testimony meets the standards of admissibility set forth in the Tennessee Rules of Evidence" (Tenn. Code Ann. § 24-7-117[b][1]). "DNA analysis" is defined broadly to mean "the process through which deoxyribonucleic acid (DNA) in a human biological specimen is analyzed and compared with DNA from another biological specimen for identification purposes" Id. at § 24-7-117(a). Some statutes explicitly identify a type of DNA analysis, e.g., 10 Md. Code Ann. § 915(b) ("an analysis that utilizes the restriction fragment length polymorphism analysis of DNA"). For discussions, see Moenssens, Starrs, Henderson and Inbau (1995, § 15.20) (surveying criminal and civil statutes); Kaye and Kanwischer (1988) (cataloging civil statutes); Liebeschuetz (1991); Jakubaitis (1991); O'Brien (1994).

13

For an unusual exception, see Kelly v State, 792 S.W. 2d 579 (Tex. App. 1990) (admitting a VNTR profile match where the state produced five experts who were seriously challenged by only one defense expert, who said that "radioactive technology was too new to be generally accepted in the scientific community"), aff'd, 824 S.W. 2d 568 (Tex. Crim. App. 1992). Although the vast bulk of the cases finding general acceptance have come in the context of VNTR profiling, similar principles and methods of molecular biology underlie the detection of coding DNA polymorphisms, STRs, minisatellite repeat mapping, and the like.

14

When a court takes judicial notice, it accepts a matter as true without requiring that it be proved. Judicial notice is reserved for matters of common knowledge or those that are capable of "accurate and ready determination by resort to sources whose accuracy cannot be questioned" Fed. R. Evid. 201(b). The 1992 NRC report suggested that the following "underpinnings" would be subject to judicial notice (p 149): "The study of DNA polymorphisms can, in principle, provide a reliable method for comparing samples; each person's DNA is unique (with the exception of identical twins), although the actual discriminatory power of any particular DNA test will depend on the sites of DNA variation examined; [and] the current laboratory procedure for detecting DNA variation (specifically, single-locus probes analyzed on Southern blots without evidence of band shifting) is fundamentally sound, although the validity of any particular implementation of the basic procedure will depend on proper characterization of the reproducibility of the system (e.g., measurement variation) and the inclusion of all necessary scientific controls."

15

E.g., United States v Perry, Crim. No. 92-474 (D.D.C. Jan. 11, 1994) (order taking "judicial notice of the reliability of the technique of DNA profiling"); State v Montalbo, 73 Haw. 130, 828 P.2d 1274 (1992) (taking judicial notice that "the DNA paradigm is not controversial and is widely accepted in the relevant scientific community"); People v Adams, 195 Mich. App. 267, 489 N.W.2d 192 (1992) ("trial courts may take judicial notice of the reliability of DNA identification testing," but "the prosecutor must establish in each particular case that the generally accepted laboratory procedures were followed"); State v Woodall, 182 W. Va. 15, 385 S.E.2d 253 (1989) (taking judicial notice of general scientific acceptance where there was no expert testimony, but holding that inconclusive results were properly excluded as irrelevant). But cf. State v Hammond, 221 Conn. 264, 604 A.2d 793 (1992) (''Unlike some courts . . . , we regard DNA typing as too novel for its reliability to be judicially noticed at this time.").

16

E.g., State v Peters, 192 Wis. 2d 674, 534 N.W.2d 867 (Ct. App. 1995) ("Unlike judges in Frye and Daubert jurisdictions, this role is much more oblique and does not involve a direct determination as to the reliability of the scientific principle on which the evidence is based .... Although Wisconsin judges do not evaluate the reliability of scientific evidence, they may restrict the admissibility of such evidence through their limited gatekeeping functions."). For a survey of the reactions of state courts to Daubert, see Meaney (1995).

17

McCormick (1992, § 203). With many, if not most, types of scientific evidence, admissibility does not seem to turn on the choice of the label. For example, by and large, polygraph evidence is inadmissible in both general-acceptance and sound-methodology jurisdictions. With DNA identification, however, a different pattern might be emerging. Over the last several years, appellate courts in Frye jurisdictions have seemed more prone than appellate courts in other jurisdictions to regard the admission of single-locus VNTR tests as error. See State v Anderson, 118 N.M. 284, 295-96, 881 P. 2d 29, 40-41 (1994) (collecting cases); State v Streich, 658 A. 2d 38 (Vt. 1995) ("We note that the courts that refuse to accept statistics based on the unmodified product method continue to rely on the more narrow Frye standard.").

18

Blake et al. (1992, p 707) report that "[t]he first use of PCR in a criminal case" occurred in a 1986 Pennsylvania case entitled Commonwealth v Pestinikis. This application of an early form of the DQA test appears to be the first instance of forensic DNA testing of any kind in this country. The first appellate opinion on the admissibility of DNA testing is Andrews v State, 533 So. 2d 841 (Fla. Dist. Ct. App. 1988), and it involved VNTR profiling.

19

See, e.g., Cobey v State, 559 A.2d 391 (Md. Ct. Spec. App. 1988) (prosecution produced five experts to testify to general acceptance of VNTR probes; defense called no experts); Kaye (1991. p 357 n 17); Thompson and Ford (1989).

20

Caldwell v State, 393 S.E.2d 436 (Ga. 1990) (finding Lifecodes "straight binning method satisfactory," but because the laboratory's calculation that the frequency of the profile in the population was 1/24,000,000 rested on the assumption of HW proportions was inconsistent with its database, held that the more conservative figure of 1/250,000 derived from that database would have to be used).

21

Commonwealth v Curnin, 565 N.E.2d 440 (Mass. 1991) (holding that Cellmark DNA evidence in a rape case had been erroneously admitted in the absence of a showing of the general acceptance of the validity of the product rule, which gave a frequency of 1/(59 million)).

22

State v Schwartz, 447 N.W.2d 422, 428 (Minn. 1989) (responding to VNTR analysis, said to produce a "banding pattern [whose frequency] in the Caucasian population is approximately I in 33 billion," the court concluded that "DNA typing has gained general acceptance in the scientific community" but that "the laboratory in this case did not comport" with "appropriate standards," and further holding the statistical conclusion to be inadmissible because even if the computation is accurate, "we remain convinced that juries in criminal cases may give undue weight and deference to presented statistical evidence'').

23

Other courts have also refused to admit some forms of DNA evidence. See, e.g., United States v Two Bulls, 918 F.2d 56 (8th Cir. 1990), vacated for rehearing en banc but appeal dismissed due to death of defendant, 925 F.2d 1127 (8th Cir. 1991); People v Castro, 545 N.Y.S.2d 985 (Sup. Ct. 1989); cf. Perry v State, 586 So.2d 242 (Ala. 1991) (remanding for hearing on Lifecodes's adherence to proper procedures and acceptability of statistical methods).

24

See, e.g., United States v Jakobetz, 747 F. Supp. 250 (D. Vt. 1990) (applying relevance standard), aff'd, 955 F.2d 786 (2d Cir. 1992), cert. denied, 113 S.Ct. 104 (1992); United States v Yee, 134 F.R.D. 161 (N.D. Ohio 1991) (applying general-acceptance standard), aff'd sub nom. United States v Bonds, 12 F.3d 540 (6th Cir. 1993); cf. State v Pierce, 597 N.E.2d 107 (Ohio 1992) (applying relevance standard, no defense experts); Satcher v Commonwealth, 421 S.E.2d 821 (Va. 1992) (applying general-acceptance standard and statute, no defense experts).

25

For reviews of the case law, see, e.g., Kaye (1993, 1994); Thompson (1993). It remains possible that some unreported cases have reached a contrary result.

26

E.g., Fishback v People, 851 P.2d 884, 893 (Colo. 1993) (trial courts may take judicial notice of the acceptability of the techniques used in RFLP analysis); State v Moore, 885 P.2d 457 (Mont. 1994) ("the theory underlying DNA and RFLP technology is not open to serious attack"); State v Streich, 658 A.2d 38 (Vt. 1995) (this "part of the scientific debate has essentially ended in favor of DNA admissibility").

27

United States v Jakobetz, 747 F. Supp. 250 (D. Vt. 1990), aff'd, 955 F.2d 786 (2d Cir. 1992), cert. denied, 113 S. Ct. 109 (1992); United States v Yee, 134 F.R.D. 161 (N.D. Ohio 1991), aff'd sub nom, United States v Bonds, 12 F.3d 540 (6th Cir. 1993). Those arguments have no application to PCR-based methods that use discrete markers.

28

From a statistical standpoint, the window is best understood in terms of the "standard error" of measurement—a quantity that indicates the variability in repeated measurements of DNA fragments of the same size—and can differ from one laboratory to another. As explained in Chapter 5, match windows must be wider than the normal variability to permit a declaration that two fragments match in most of the cases when they are actually the same length. But the window should not be so wide as typically to produce declarations of matches between fragments that are not about the same size (see Chapter 5). The result is a wide range of possible match windows. Cf. Roeder 1994, p 275 ("the 'objective' match criterion ... is, in fact, simply an arbitrary rule"). In these circumstances, it has been suggested that expert testimony that narrower windows would have excluded a defendant is tautological and more prejudicial than probative (Kaye 1993, 1995). A brief argument to the contrary is made in Thompson (1993).

29

Cf. People v Venegas, 36 Cal. Rptr. 2d 856 (Ct. App. 1995) (observing that because "the [1992] NRC report expressed approval of the fixed bin method as an alternative to the NRC's 'floating bin' method . . . there is no need for the FBI to abandon that method in order to find consensus in the NRC methodology"), rev. granted, 39 Cal. Rptr. 2d 408, 890 P. 2d 1117.

30

See Blake et al. (1992, p 720) ("As of September 1991, the HLA-DQA test has been introduced as courtroom evidence into 44 cases and has been evaluated in 25 admissibility hearings in 20 different states"). As of November 10, 1995, 34 cases in which PCR-based DNA testing had been conducted could be retrieved from the Westlaw "allcases" database of court opinions. A survey with responses from 49 forensic laboratories, conducted in November 1994, revealed over 280 cases where PCR-based typing results were introduced in courts in 37 states (Perkin Elmer Corp. 1995, at 1).

31

See, e.g., Harrison v State, 644 N.E.2d 1243, 1251 (Ind. 1995) ("The words 'DNA test results' are not magic words which once uttered cause the doors of admissibility to open."); State v Russell, 125 Wash.2d 570, 882 P.2d 747 (1995) ("The issue in this case is thus not whether the underlying theory of DNA testing is generally accepted, but whether the PCR technique is generally accepted."); State v Grayson, No. K2-94-1298, 1994 WL 670312 (Minn. Dist. Ct. Nov 8, 1994) (although RFLP testing is accepted in Minnesota, court re-examined PCR-based testing according to the Frye standard). Consequently, judicial opinions on the admissibility of PCR-based evidence illuminate the procedures that judges use in determining the validity of a new DNA technology, in addition to elucidating particular legal issues generated by the PCR method of DNA typing. See, e.g., State v Gentry, 125 Wash.2d 570, 888 P.2d 1105 (1995) (1995) (6-week Frye hearing).

32

Serritt v State, 647 So. 2d 1 (Ala. Crim. App. 1994); People v Amundson, 34 Cal. App. 4th 1151, 41 Cal. Rptr. 2d 127 (1995) ("Since [the 1992 NRC] report was written, the reliability of PCR testing for forensic use has consistently been proven by the testimony of experts, hundreds of authoritative scientific articles and other literature supporting this typing technique, and by the overwhelming acceptance of PCR testing in dozens of judicial decisions."); People v Groves, 854 P.2d 1310 (Colo. Ct. App. 1992); State v Hill, 859 P.2d 1238 (Kan. 1995) (generally accepted); State v Hoff, 904S.W.2d 56 (Mo. Ct. App. 1995) (generally accepted); State v Moore, 885 P.2d 457 (Mont. 1994) (DQA inclusion and exclusions satisfy Daubert standard); State v Williams, 599 A.2d 960 (N.J. Super. Ct. 1991) ("hundreds" of scientific articles); State v Lyons, 863 P.2d 1303 (Or. Ct. App. 1993) (PCR methodology used forensically in eight states and adopted by several state and private forensic laboratories and FBI; extensive peer-reviewed literature); Trimboli v State, 826 S.W.2d 953 (Tex. Crim. App. 1992); Clarke v State, 813 S.W.2d 654 (Tex. App. 1991); State v Gentry, 888 P.2d 1105 (Wash. 1995) (generally accepted); State v Russell, 125 Wash. 2d 24, 882 P. 2d 747 (1994) (court notes extensive validation studies on PCR testing in holding the Frye test satisfied).

33

State v Carter, 524 N.W.2d 763, 769 (Neb. 1994); State v Grayson, No. K2-94-1298, 1994 WL 670312 (Minn. Dist. Ct. Nov 8, 1994) ("means to exclude possible defendants rather than identify"); State v Penton, No. 9-91-25, 1993 WL 102507 (Ohio Ct. App. Apr. 7, 1993) ("Unlike RFLP/DNA analysis, PCR/DNA can not get you down to one person but excludes a percentage of the population."), app. dismissed, 619 N.E.2d 698, 617 Ohio St. 3d 1464 (1993).

34

In the reported cases, PCR typing usually was done with a DQ Alpha kit. But see People v Morales, N.Y.L.J.. Oct. 26, 1994, at 34, col. 6 (Rockland County Ct.). (Amplitype PM or Polymarker test, as well as DQA test, admitted); cf. State v Russell, 125 Wash. 2d 24, 882 P. 2d 747, 768 (1994) (as other modes of testing are developed, "any concerns about implementation in a given case are matters to be addressed to the trial court pursuant to E[vidence] R[ule] 702").

35

These loci can be analyzed with further PCR-based tests, with VNTR systems, or with traditional protein markers. See, e.g., People v Simpson, No. BA097211 (Super. Ct., Los Angeles Cty., 1995) (VNTR, DQA, Polymarker, ABO, and PGM markers); State v Gentry, 125 Wash.2d 570 (Wash. 199 5) (using ABO, GM, haptoglobin, and PCR-based results, an expert testified that the combined frequency in the Caucasian population was 0.18%, whereas the frequency for the PCR type was 8%).

36

E.g., People v Amundson, 41 Cal. Rprt. 2d 127 (Ct. App. 1995) ("the report's observation that PCR analysis has not yet received 'full acceptance' for forensic use is not a valid criticism . . . a new scientific technique need only have gained 'general acceptance'"), rev. granted; State v Russell, 882 P.2d 747, 762 (Wash. 1994). The 1992 NRC report expressed reservations about PCR-based testing for forensic use (p 70), the dangers of contamination (p 65-67), differential amplification (pp. 64-65), and misuse of testing kits by "nonexpert laboratories" (p 69).

37

See State v Gentry, 125 P.2d 570 (Wash. 1995) (dissent cites 1992 report as establishing that PCR testing was "not yet generally accepted as a methodology capable of consistently producing reliable results on forensic samples").

38

But see State v Russell, 882 P.2d 747, 767 (Wash. 1994) (also discussing dangers of differential amplification and misincorporation).

39

E.g., State v Lyons, 863 P.2d 1303, 1309 (Or. Ct. App. 1993) ("The potential for contamination presents an 'open field' for cross-examination at trial, but does not indicate that the PCR method is inappropriate for forensic use."); State v Russell, 882 P.2d 747 (Wash. 1994) (discussing 1992 NRC report, but finding PCR-based evidence admissible after noting that over 30 forensic laboratories were performing DQA testing as of March 1991, that the FBI began using the Cetus kit in 1992. that the British Home Office had adopted DQA as its screening test, and that problems of laboratory error are "either detectable or preventable" when proper techniques and laboratory procedures are used). In theory, a court could find a particular PCR-based test performed in such a substandard way as to justify exclusion of the evidence. Cf. State v Moore, 885 P.2d 457, 474-75 (Mont. 1994) (DQA test results admissible despite concern about contamination expressed in 1992 NRC report because "the experts handling the piece of brain tissue were aware of the possibility of contamination, and took appropriate steps to avoid and detect contamination").

40

State v Streich, 658 A.2d 38 (Vt. 1995) ("The [RFLP] process is not error-free, but adherence to accepted procedures and controls minimizes this error. . . . We cannot find any recent decision under any standard of admissibility which refuses to admit the DNA match result based on the invalidity or risk of error of the underlying technology.").

41

Compare United States v Two Bulls, 918 F.2d 56 (8th Cir. 1990), vacated for rehearing en banc but appeal dismissed due to death of defendant, 925 F.2d 1127 (1991); Perry v State, 586 So. 2d 242 (Ala. 1991); People v Barney, 8 Cal. App. 4th 798, 10 Cal. Rptr. 2d 731 (1992); Commonwealth v Curnin, 409 Mass. 218, 565 N.E.2d 440 (1991) (dictum); Commonwealth v Rodgers, 605 A.2d 1228 (Pa. Super. 1992); Barnes v State, 839 S.W.2d 118 (Tex. App. 1992) (requiring clear and convincing evidence of compliance) with State v Bible, 858 P.2d 1152 (Ariz. 1993), cert. denied, 114 S.Ct. 1578 (1994); People v Stremmel, 258 N.E.2d 93 (111. App. 1994); Davidson v State, 580 N.E. 2d 238 (Ind. 1991); State v Vandebogart, 616 A.2d 483 (N.H. 1992); State v Cauthron, 120 Wash. 2d 879, 846 P.2d 502 (1993).

42

Cf. McCormick ( 1992, § 203, at 875 n.41) (proposing external proficiency testing as a prerequisite to admissibility); Jonakait (1991). Courts also could refer to regular participation in accreditation programs, proficiency-testing and independent audits when instructing the jury, allowing jurors to draw a negative inference from the absence of these quality control mechanisms. In addition to providing the jury with valuable guidance, wide use of this instruction would encourage laboratories to participate in such activities. An instruction might read: "In evaluating the quality of the DNA evidence, you might wish to consider the laboratory's participation or nonparticipation in the following quality control activities: (1) accreditation; (2) proficiency-testing, particularly proficiency-testing with blind samples; and (3) independent audits."

43

In the federal courts, Rule 16(a)(l)(C) of the Federal Rules of Criminal Procedure—which authorizes, on defendant's request, inspection of tangible objects in the government's possession—has been interpreted to mandate a defendant's right to test or retest a sample in the government's control. See, e.g., United States v Butler, 988 F.2d 537 (5th Cir. 1993) (cocaine), cert. denied, 114 S.Ct. 413 (1993). Some states similarly construe their jurisdiction's criminal-discovery rules as mandating retesting (Annotation 1984). Other states have statutes or rules that specifically provide for the retesting of physical evidence. See, e.g., Iowa Code Ann. § 813.2, R. 13(2)(b)(1) (1979); La. Code Crim. Part 71 (West 1981 ); State v Schwartz, 447 N.W.2d 422, 427 (Minn. 1989) (relying on a Minnesota rule of criminal procedure giving defense counsel the right to "inspect and reproduce any results of any ... scientific tests, experiments or comparisons made in connection with the particular case" to conclude that, whenever practical, "a defendant should be provided with the actual DNA sample(s) in order to reproduce the tests"). In addition, some authority supports a constitutional right to retest, stemming from the requirement of due process. See, e.g.. Moore v State, 748 P.2d 732, 735 (Ok. Crim. App. 1987) (Oklahoma constitution requires the state to afford the accused an opportunity to re-examine and retest unless the sample was consumed by government testing; illegal substance); State v Thomas, 421 S.E.2d 227, 234 (W.Va. 1992) (if the prosecution conducts a test, such as an electrophoretic blood test, that consumes the sample being tested, the state must "preserve as much documentation of the test as is reasonably possible to allow for a full and fair examination of the results by a defendant and his experts"). Other courts, however. have found that even when retesting was refused, sufficient protection for the accused was afforded by the right to cross-examine the prosecution's expert. See, e.g., Frias v State, 547 N.E.2d 809, 813 (Ind. 1989) (cocaine), cert. denied, 495 U.S. 921 (1990); People v Bell, 253 N.W.2d 726. 729 (1977); Montoya (1995).

44

Compare State v Faraone, 425 A.2d 523, 526 (R.I. 1981) ("The court may [after the defendant moves for testing] in its discretion, provide for appropriate safeguards, including where necessary, the performance of such tests at the state laboratory under the supervision of the state's analyst.") with Prince v Superior Court, 8 Cal. App. 4th 1176, 1179, 10 Cal. Rptr. 2d 855, 857 (1992) (defendant entitled to independent testing).

45

See, e.g., State v Faraone, 425 A.2d 523, 526 (R.I. 1981) (requiring defendant to file a motion "setting forth the circumstances of the proposed analysis, the identity of the expert who will conduct such analysis, his qualifications, and scientific background").

46

See, e.g., Hicks v State, 352 S.E.2d 762, 769 (Ga.) (it is not an error to deny a request for independent analysis of blood samples if the trial court had offered the defendant an opportunity to have the state crime laboratory perform additional tests and had left open the possibility of a forensic expert for the defendant if necessity was shown; capital case), cert. denied, 482 U.S. 931 (1987).

47

Cf. Harrison v State, 644 N.E.2d 1243, 1253 (Ind. 1995) (in finding no abuse of discretion in failing to appoint a defense expert, the court noted that "there was every reason to believe that" experts who had performed testing for the prosecution were neutral).

48

Statutes also play a role; some set limits, which can be quite low, on the compensation for experts and other defense services. E.g., Tex. Crim. Proc. Code Ann. art. 26.05 § 1(d) (Vernon 1989 & Supp. 1994) (maximum, $1,000).

49

See, e.g., Dubose v State, 662 So.2d 1189 (Ala. 1995) (it is a due-process violation not to provide an expert "to refute the testimony of the Lifecodes witnesses . . . to independently test the samples, to question whether the DNA results, in fact, showed a match, or to explain that scientific opinion may be divided"); Cade v State, 658 So. 2d 550 (Fla. Ct. App. 1995) (trial court abused its discretion under state statute by denying defense request for appointment of DNA expert even though there was no showing of specific need, but only the general observation that "I can't tell the Court what I'm looking for because it's so complicated"), rev. denied, 663 So. 2d 631 (Fla. 1995); Husske v Commonwealth, 448 S.E.2d 331, 335 (Va. Ct. App. 1994) (it depends on how important the scientific issue is in the case and how much help a defense expert could have given; it is an error not to provide an expert to challenge the numbers and assertions of a population geneticist).

50

Harrison v State, 644 N.E.2d 1243 (Ind. 1995) (there is no error in failing to provide an expert in a capital case; the court stresses that Ake was concerned with expertise of a very subjective nature, whereas DNA testing involved precise physical measurements performed by an independent laboratory, and the defendant had not made any showing of what the laboratory might have done inaccurately); State v Harris, 866 S.W.2d 583 (Tenn. Crim. App. 1992) (insufficient showing of particularized need). The more detailed a showing the court requests as to precisely what issues in the case necessitate expert assistance, the less likely it is that a defense counsel unsophisticated about DNA testing will be able to satisfy the court.

51

Many subsidiary questions can arise: Would such a comment chill the defendant's right to effective assistance of counsel because defendants would not avail themselves of the opportunity to retest if this provided ammunition for the prosecution? Would such a comment impermissibly shift to the defendant a burden to produce evidence? To what extent does it matter whether the defense has called witnesses in its behalf instead of merely cross-examining the prosecution's expert? Would such a comment be unfair if the defendant were indigent and the jurisdiction did not provide defendants with experts in DNA typing? proceed ex parte (see 18 U.S.C. § 3006A (e)), in many instances this provision would preclude the prosecution from knowing a defendant's plans. With DNA evidence, however, the prosecution will know that the defense wishes to retest because the samples have to be turned over. Nevertheless, it has been suggested that the restriction on discovery should be interpreted as barring the prosecution from calling the defense expert (Contra State v McDaniel, 485 N.W.2d 630 [Iowa 1992]).

52

See State v Gentry, 888 P.2d 1105, 1121-1122 (Wash. 1995) (the trial court ruled that questions to experts about whether they had retested forensic samples were permissible but that questions about whether they could have done so were impermissible and gave curative instruction on the prosecution's burden of proof; appellate court stated: "While it is questionable whether asking scientific experts whether they did, or could have, conducted duplicate testing is error at all, in this case any possible error in confusing the jury as to the burden of proof was cured by the trial court's simultaneous curative instructions."). See also State v Jobe, 486 N.W.2d 407, 418 (Minn. 1992) (the court found that the prosecutor's question to the defense's DNA expert, who was critical of FBI's testing procedures, as to "whether he could do that type of procedure in his laboratory if samples were provided" did not impermissibly shift the burden of proof, because it did not suggest that the "appellant was obligated to pursue independent testing").

53

When the defense calls its expert to testify, it waives some privileges: United States v Nobles, 422 U.S. 225, 239 (1975) (work product); United States v Alvarez, 519 F.2d 1036, 1046-47 (3d Cir. 1975) (attorney-client privilege).

54

Compare Giannelli (1991, p 819) ("retesting comes with a price tag. The prosecution could introduce evidence that samples had been turned over to the defense with the opportunity for retesting and then comment to the jury on the defense's failure to introduce the test results.") with Scheck (1994, p 1969 n 33) ("there should be no requirement that the results [of defense tests] be disclosed").

55

In Ake v Oklahoma, 470 U.S. 68 (1985), the Supreme Court rested its decision requiring the state to provide expert psychiatric assistance to the defendant on the due-process clause. It has been suggested that a rule that infringes on the right of a defendant to obtain expert assistance by making that right costly "subverts this due process right" (Maringer 1993, p 656 n 11). Due process also is implicated to the extent that a comment impermissibly shifts the prosecution's burden of proof to the defendant.

56

See, e.g., Prince v Superior Court, 8 Cal. App. 4th 1176, 1179, 10 Cal. Rptr. 2d 855, 857 (1992) (an order that would require defendant to turn over the results of DNA testing even if it did not introduce this evidence at trial denied the defendant the effective assistance of counsel); State v Melvins, 382 A.2d 925 (N.J. Super. 1978) (an order requiring production of copies of a defense expert's investigative reports violated the Sixth Amendment if the defense was not planning to call the expert as witness). But see State v McDaniel, 485 N.W.2d 630, 633 (Iowa 1992) (prosecution use of an expert provided an indigent defendant violates neither due process nor effective assistance of counsel).

57

The majority rule appears to be that the attorney-client privilege covers communication between experts and attorneys and that consequently the privilege prevents the prosecution from calling a defense-retained expert as a government witness (see Giannelli and Imwinkelried 1993, § 5-10). There are, however, cases that find either that the expert is not an agent of the attorney or that the privilege applies only to experts, such as psychiatrists, who rely on the defendant's communication in reaching their opinions. Id. See also Mosteller (1986).

58

See Imwinkelried (1990) (arguing that work product, rather than privilege, should apply so that prosecution can obtain a defense witness's opinion on a showing of need).

59

Rule 16 of the Federal Rules of Criminal Procedure requires the defense to advise the prosecution of the results of scientific tests only if it intends to introduce the results in its case in chief. Especially when coupled with a requirement that defense applications for "investigative, expert or other services"

60

See California v Trombetta, 467 U.S. 479 (1984) (failure to preserve a breath sample did not amount to a lack of due process). With the advent of PCR testing, the prosecution's choice of a method that will consume a sample, rather than replicate it, might become an issue. See, e.g., People v Griffin, 761 P.2d 103, 107. 46 Cal.3d 1011, 1021-1022, 251 Cal. Rptr. 643, 647-48 (1988) (en banc) (surveys cases in which courts have suggested that prosecution has burden of showing that its destruction of the sample was reasonable). When the defense tests a sample to which the prosecution has not had access, it may not keep the results secret if the testing consumes the sample. See, e.g., State v Cosey, 652 So.2d 993, 994 (1995); People v Cooper, 809 P.2d 865, 889, 53 Cal.3d 771, 815, 281 Cal. Rptr. 90, 114 (1991) (en banc).

61

Arizona v Youngblood, 488 U.S. 51 (1988) (the prosecution's failure to preserve evidence and to perform genetic-marker tests did not amount to a denial of due process). But cf. Colo. Rev. Stat. § 16-3-309 (1986) (setting forth factors that a court should consider in deciding whether to admit results of a test that consumed a sample, making independent testing impossible).

62

Obviously, the defense can make such an arrangement only if it is provided adequate notice of the prosecution's plans for testing and if it has retained an expert. See, e.g., Commonwealth v Gliniewicz, 500 N.E.2d 1324, 1327 (1986) (in holding that the prosecution's actions violated a pretrial agreement, the court noted that "defendants received no notice of the impending tests, and thus were not able to have their own expert present to observe and potentially to refute the subjective aspects of the [blood] testing"). The value of having defense experts present, however, has been questioned (see Wooley 1995).

63

See, e.g., People v Garries, 645 P.2d 1306 (Colo. 1982) (test results were suppressed where blood samples were consumed, and the defendant had no opportunity to be present and no photographs were taken); State v Schwartz, 447 N.W.2d 422, 427 (Minn. 1989) (because "forensic samples are often so small that the entire sample is used in testing, . . . access to the data, methods, and actual results is crucial"). See also People v Griffin, 761 P.2d 103, 107, 46 Cal.3d 1011, 1021-1022. 251 Cal.Rptr. 643, 647-48 (1988) (en banc) (surveys cases in which courts have suggested that prosecution has burden of showing that its destruction of the sample was reasonable).

64

State v Streich, 658 A.2d 38 (Vt. 1995) ("We note that the courts that refuse to accept statistics based on the unmodified product method continue to rely on the more narrow Frye standard," but the court reached the same result under the Daubert standard).

65

For example, one early criticism of the allele-frequency estimates focused on the FBI's reliance on a database consisting of FBI agents. E.g., United States v Jakobetz, 747 F. Supp. 250 (D. Vt. 1990), aff'd, 955 F.2d 786 (2d Cir. 1992), cert. denied, 113 S. Ct. 109 (1992); United States v Bonds, 12 F.3d 540 (6th Cir. 1993).

66

State v Bible, 858 P.2d 1152, 1186 (Ariz. 1993); State v Buckner, 125 P.2d 915 (Wa. 1995) (although "the sample must be truly random," the ceiling calculation could account for a departure from randomness).

67

Neither the courts nor the experts are always careful to specify the population that is of interest. Population structure is less of an issue when one seeks to estimate the frequency within a racial group than in a small, genetically isolated subpopulation. See, e.g., Kaye (1993) (suggesting that the published criticism of the usual multiplication procedure occurs only in the context of making subpopulation estimates).

68

See, e.g., Lindsey v People, 892 P.2d 281 (Colo. 1995) (suggesting that general acceptance was more easily found before 1992 NRC report); State v Carter, 246 Neb. 953, 524 N.W.2d 763, 782 (1994) ("The report . . . is persuasive regarding the lack of general acceptance.... Before [its] issuance . . . statistical estimates calculated by forensic laboratories were routinely ruled admissible in most cases; however, since the issuance, an overwhelming majority of courts have excluded evidence of a match after finding that there is no general acceptance as to the statistical probability calculations due to the division in the scientific community on the issue of population substructure."). For a more complete review of the cases after the publication of the 1992 report, see Kaye (1995).

69

People v Wilds, 37 Cal. Rptr. 2d 351 (Ct. App. 1995), rev. granted. See also People v Amundson, 41 Cal. Rptr. 2d 127 (Ct. App. 1995) ("the scientific landscape has once again changed"), rev. granted; People v Marlow, 41 Cal. Rptr. 2d 5 (Ct. App. 1995) ("Since Lewontin's and Hartl's article . . . numerous studies have been published in scientific journals compiling VNTR frequency data from around the world. These studies have empirically demonstrated the very conservative nature of the frequency calculation methods employed by forensic laboratories. . . . The weight of authority in the published peer-reviewed literature overwhelmingly supports the proposition that VNTR frequency differences due to ethnicity or substructuring have little impact on DNA population frequency estimates . . . ." ), rev. granted; People v Soto, 35 Cal. Rptr. 2d 846 (Ct. App. 1994), ("We now have data showing that population substructuring is not 'forensically significant' in estimating the random likelihood of a particular DNA profile."), rev. granted; Taylor v State, 889 P.2d 319 (Okla. Ct. Crim. App. 1995) (reiterating the conclusion of People v Soto that "several scientific developments

70

The supreme court of Nebraska, for example, while finding a PCR-based match sufficiently reliable to satisfy its Frye standard, reversed a conviction on the grounds that no general acceptance exists with regard to the calculation of the probability to which the state's experts testified: State v Carter, 524 N.W.2d 763 (Neb. 1994) (relies on 1992 NRC report as indicating lack of general acceptance and states that limiting statistical estimates to two racial groups when the racial or ethnic background of the perpetrator is unknown is prejudicial).

71

People v Venegas, 36 Cal. Rptr. 2d 856 (Ct. App. 1995) (an FBI expert reported a three-locus match for "DNA characteristics as shared by one person out of 65,000 in the general population, and one out of 30,000 in the southwestern United States Hispanic population"; "the defense genetics expert ... concluded that . . . depending on his choice of methodology, . . . one out of 35 or one out of 378 persons shared appellant's DNA profile."), rev. granted. Discrepancies sometimes occur in the figures quoted for ceiling frequencies by prosecution experts alone. E.g., People v Marlow, 41 Cal. Rptr. 2d 5 (Ct. App. 1995) (such estimates ranged from 1/105,000 to 1/27,000), rev. granted; cf. Taylor v State, 889 P.2d 319 (Okla. Ct. Crim. App. 1995) (the state's expert produced figures of 1/(97 billion), 1/(334 billion), and, "using Lifecodes's current, more conservative approach" of "straight binning," 1/(10 billion)). Discrepancies between unadjusted figures and ceiling frequencies are even more dramatic. E.g., id. (1/7,400,000-1/33,000,000 without adjustment); People v Wilds, 37 Cal. Rptr. 2d 351 (Ct. App. 1995) ("Cellmark's original probability estimate of a random-match included a calculation of I in 186 billion. Using a more conservative approach, the estimate was reduced to I in 66 million. At a pre-trial hearing, Dr. Kidd applied statistically unreasonably conservative' assumptions to Cellmark's data and calculated a probability of I in 1.86 million. Based on an expanded data base which was available at the time of trial, Dr. Kidd revised his probability estimate to 1 in 4.5 million."), rev. granted; Lindsey v People, 892 P.2d 281 Colo. 1995) (estimates of "the probability that Lindsey's DNA profile would match the profile of a randomly selected African American individual . . . ranged from one in 340 billion down to one in 21 million using more conservative frequency calculations"); Brim v State, 654 So. 2d 184 (Fla. Dist. Ct. App. 1995) ("the FBI procedure [used by the Florida state laboratory] generated a probability that only one out of 1.4 billion whites and one out of 2.5 million blacks would share the DNA code ... The modified ceiling principle indicated that only one in just over 9,000 individuals would share the perpetrator's genetic DNA code."); Commonwealth v Lanigan, 419 Mass. 15, 641 N.E.2d 1342 (1994) (interim ceiling estimate changed VNTR probability "from only one in more than 2,000,000 ... to a range of one in 311,000 to one in 108,000"). Still larger figures can be obtained with the ''counting method." E.g., People v Marlow, 41 Cal. Rptr. 2d 5 (Ct. App. 1995) (the laboratory's expert witness reported figures ranging from high of 1 in 33 million to a low of I in 7.4 billion for the frequency of the defendant's four-locus VNTR profile in various populations; the defense expert reported that it "might be as common as one in 211"), rev. granted. Because the opinions are not always clear about which "conservative" method is being used, it is not always easy to discern how much of the variation in the estimates can be attributed to ambiguities in the interim ceiling method or to choices among other competing procedures.

72

The 1992 report was not explicit on this point. The interim ceiling principle does not purport to measure the frequency of an incriminating profile in the reference population, but rather an upper limit of the random-match probability that is unrelated to the reference population. In late 1994, one of the authors of that report, and an early advocate of the ceiling procedure, expressed his belief that the committee intended to offer ceiling frequencies as a supplement rather than as a necessary substitute for estimates derived from data on the population or subpopulation of interest (Lander and Budowle 1994).

73

State v Sivri, 646 A.2d 169 (Conn. 1994); State v Carter, 246 Neb. 953, 524 N.W.2d 763 (1994) (the NRC report indicates a lack of general acceptance of HW proportions, which renders testimony of a PCR-based DQA test result said to include about 7% of the population inadmissible under Frye).

74

United States v Porter, 618 A.2d 629 (DC App. 1992); People v Watson, 629 N.E.2d 634 (111. App. 1994); Commonwealth v Lanigan, 596 N.E.2d 311 (Mass. 1992); State v Vandebogart, 616 A.2d 483 (Vt. 1992). In Franson v Mitchell, 206 111. Dec. 399, 645 N.E. 2d 404 (I11. Ct. App. 1994), the court determined that questions about the effect of population structure made a "probability of paternity" of 99.99% and a "cumulative paternity index" (likelihood ratio) of 29,217,637 inadmissible under Frye. It remanded for a determination of whether the more conservative methods proposed in the 1992 report had achieved general acceptance for parentage determinations. As we observed in Chapter 5, however, the ceiling methods were not proposed or designed for computing a paternity index, and the 1992 report's call for "conservative" procedures was influenced by its interpretation of the ''beyond a reasonable doubt" standard of proof used in criminal, but not civil, cases.

75

People v Venegas, 36 Cal. Rptr. 2d 856 (Ct. App. 1995), rev. granted; State v Bloom, 516 N.W.2d 159 (Minn. 1994); State v Alt, 504 N.W.2d 38 (Minn. Ct. App. 1993); State v Streich, 658 A.2d 38 (Vt. 1995); State v Cauthron, 846 P.2d 502 (Wash. 1993).

76

People v Wallace, 14 Cal. App. 4th 651, 17 Cal. Rptr. 2d 721 (1993). See also Hayes v State, 660 So. 2d 257 (Fla. 1995) (dictum); State v Hollis, No. 92-1-04603-9 (Wash. Super Ct. King County, June 1993), appeal pending, No. 3307-1-L.

77

State v Johnson, 183 Ariz. 623 (Ct. App. 1995) ("most of the remaining debate stems from criticisms that the ceiling method is too conservative, that evidence of population substructure is lacking, and that further study is needed to determine the best means of presenting probability statistics to juries, not [from any doubts about] the ceiling method's validity as a reliable and highly conservative forensic tool"), rev. granted; People v Venegas, 36 Cal. Rptr. 2d 856 (Ct. App. 1995) (noting general agreement that interim ceiling calculations have "forensic reliability"), rev. granted; United States v Porter, 618 A.2d 629 (DC Ct. App. 1992); Commonwealth v Lanigan, 419 Mass. 15, 641 N.E.2d 1342 (1994) ("the great weight of opinion appears to be" that "the answer given by the ceiling principle is . . . either irrationally conservative and thus absurd or a reasonable means of producing admissible probability evidence untainted by potential problems of population substructuring"); State v Alt, 504 N.W.2d 38 (Minn. Ct. App. 1993); State v Vandebogart, 616 A.2d 483 (N.H. 1994) (affirming trial court's findings on remand "that there is 'universal' consensus in the scientific community of geneticists and forensic DNA scientists that the interim ceiling principle properly accounts for the possibility of population substructure by providing a highly conservative estimate" and that, although those estimates "may be so conservative as to be deemed not accurate, it is nonetheless generally accepted ... that any possible errors in such estimates favor the defendant"); State v Streich, 658 A.2d 38 (Vt. 1995) ("There is general acceptance within the scientific community that the ceiling principle over-compensates for any population substructure or allele linkage.'').

78

For example, in United States v Chischilly, 30 F.3d 1144 (9th Cir. 1993), a jury convicted the defendant of raping and murdering a woman in a remote part of the Navajo Indian reservation in Arizona. Single-locus VNTR tests performed by the FBI indicated a match between sperm found on the victim and a sample of the defendant's blood. A population geneticist testified that a probability of 1/2,563 would be a "conservative estimate" of the probability of a match with a randomly selected American Indian. That probability was not obtained with the 1992 NRC report's ceiling method, but by looking to the largest profile frequency among particular tribes represented in FBI's American Indian database. The US Court of Appeals for the Ninth Circuit upheld the admission of the testimony. It reasoned that "evidence of opposing academic camps in virtual scholarly equipoise amidst the scientific journals" demonstrated more than "minimal support within a [scientific] community" and that this degree of acceptance, in combination with the other considerations listed in Daubert, militated in favor of admission. Other federal and state courts, applying the scientific-soundness standard, have held far smaller genotype-frequency estimates-both ceiling and population-specific-admissible: United States v Jakobetz, 955 F.2d 786, 800 (2d Cir.), cert. denied, 113 S.Ct. 104 (1992) (pre-Daubert opinion holding population-specific frequencies admissible); United States v Bonds, 12 F.3d 540 (6th Cir. 1993); United States v Martinez, 3 F.3d 1191 (8th Cir. 1993), cert. denied, 114 S.Ct. 734 (1994); Commonwealth v Lanigan, 419 Mass. 15, 641 N.E.2d 1342 (1994) (interim ceiling estimate properly admitted under Daubert on retrial following reversal under Frye of original conviction obtained with usual product-rule estimate); State v Duran, 881 P.2d 48 (N.M. 1994); State v Peters, 192 Wis. 2d 674, 534 N.W.2d 867 (Ct. App. 1995) (ceiling frequency properly admitted with other estimates against American Indians under relevancy standard when the trial court found that the interim ceiling method satisfied Daubert); State v Springfield, 860 P.2d 435 (Wyo. 1993) (population-specific frequencies admissible when accompanied by ceiling frequency). But see State v Streich. 457 A.2d 440 (Vt. 1995) ("even under Daubert it is inappropriate to allow evidence based on the unmodified product method. In the lexicon of Daubert, we are concerned that the accuracy of the results cannot be ensured by testing, there is an unknown potential for error, and these calculations are not generally accepted within the scientific community. The endorsement of the ceiling principle by the NRC and more recently by leading advocates in the dispute, including a representative of the FBI, leads us to this conclusion.").

79

State v Carter, 246 Neb. 953, 524 N.W.2d 763 (1994) (1992 NRC Report indicates lack of general acceptance of HW proportions, which renders testimony of a DQA test result said to include about 7% of the population inadmissible under FrYe); People v Morales (Rockland County Ct.), N.Y.L.J., Oct. 26, 1994. at 34, col. 6.

80

E.g., People v Wallace, 14 Cal. App. 4th 651, 17 Cal. Rptr. 2d 721 (1993); State v Hollis, No. 2-1-04603-9 (Wash. Super. Ct., King County, June, 1993), appeal pending, No. 3307-1-L; People v Barney, 8 Cal. App. 4th 798, 10 Cal. Rptr. 2d 731 (1992); People v Atoigue, DCA No. CR 91-95A (Guam Dist. Ct. App. Div. 1992); State v Carter, 246 Neb. 953, 524 N.W.2d 763, 782, 783 (1994) ("The calculation of statistical probability is an essential part of the process used in determining the significance of a DNA match . . .We hold that evidence of a DNA match will not be admissible if it has not been accompanied by statistical probability evidence that has been calculated from a generally accepted method."). Contra Commonwealth v Crews, 640 A.2d 395, 402 (Pa. 1994) ("The factual evidence of the physical testing of the DNA samples and the matching alleles, even without statistical conclusions, tended to make appellant's presence more likely than it would have been without the evidence, and was therefore relevant.").

81

State v Bogan, 183 Ariz. 506, 905 P.2d 515 (Ct. App. 1995), rev. granted; State v Hummert, No. CR 90-05559 (Super. Ct. Maricopa Co. Apr. 16, 1991), rev 'd for not excluding testimony thought to assert that match was unique, 183 Ariz. 493, 905 P.2d 493 (Ct. App. 1994), rev. granted; State v DeSpain, No. 15589 (Super. Ct. Yuma Co., Feb. 12, 1991); State v Pennell, 584 A.2d 513 (Del. 1989); State v Schwartz, 447 N.W.2d 422, 428 (Minn. 1989); State v Alt, 504 N.W.2d 38 (Minn. Ct. App. 1993); Polk v State, 612 So. 2d 381 (Miss. 1993) (the trial court admitted testimony of a match but excluded an accompanying population frequency estimate); State v Moore, 885 P.2d 457, 467, 468 (Mont. 1994) (the defendant was barred from challenging the fact that the trial court "refused to allow testimony concerning the statistics, but allowed the experts to testify that the RFLP and PCR test results were 'consistent' with [the defendant's DNA]," but "whether, and if so, to what extent we will allow DNA evidence without the accompanying statistical evidence in other criminal cases will be decided in a future case."); Rivera v State, 840 P.2d 933 (Wyo. 1992) (suggesting that the better practice is not to refer to probability estimates when introducing DNA results). But cf. Springfield v State, 860 P.2d 435 (Wyo. 1993) (a probability estimate was admissible).

82

See State v Hummert 183 Ariz. 493, 905 P.2d 493 (Ct. App. 1994), rev. granted; State v Cauthron, 846 P.2d 502, 516, 518 (Wash. 1993) (experts from a testing laboratory presented no "probability statistics" but one expert claimed that "the DNA could not have from anyone else on earth"); State v Buckner, 890 P.2d 460 (Wash. 1995) (testimony that the profile "would occur in only one Caucasian in 19.25 billion" and that because "this figure is almost four times the present population of the Earth, the match was unique" was improper).

83

State v Zollo, 36 Conn. App. 718 (1995) ("testimony that the chance that the DNA sample came from someone other than the defendant was 'so small that ... it would not be worth considering"' was not inadmissible as an opinion on an ultimate issue in the case "because his opinion could reasonably have aided the jury in understanding the [complex] DNA testimony"); People v Heaton, 266 I11. App. 3d 469, 640 N.E.2d 630 (1994) (an expert who used the product rule to estimate the frequency at 1/52,600 testified over objection to his opinion that the "defendant was the donor of the semen"); State v Pierce, No. 89-CA-30 (Ohio Ct. App. 1990) (affirming admission of testimony that the probability would be one in 40 billion "that the match would be a random occurrence," and "the DNA is from the same individual''), aff'd, 64 Ohio St. 3d 490, 597 N.E.2d 107 (1992); cf. State v Bogan, 905 P.2d 515, 522-23 (Ariz. Ct. App. 1995) (it was proper to allow a molecular biologist to testify, on the basis of a PCR-based analysis known as RAPD, that he "was confident the seed pods found in the truck originated from" a palo verde tree near a corpse); Commonwealth v Crews, 640 A.2d 395 (Pa. 1994) (testimony of an FBI examiner that he did not know of a single instance "where different individuals that are unrelated have been shown to have matching DNA profiles for three or four probes" was admissible under Frye despite objection to lack of a frequency estimate, which had been given at a preliminary hearing as 1/400).

84

See, e.g., State v Bloom, 516 N.W.2d 159, 160 n.2 (Minn. 1994) (a population geneticist was prepared to testify that "in his opinion the nine-locus match constituted 'overwhelming evidence that, to a reasonable degree of scientific certainty, the DNA from the victim's vaginal swab came from the [defendant], to the exclusion of all others'").

85

State v Bloom, 516 N.W.2d 159, 166-67 (Minn. 1994) ("Since it may be impossible to reach a consensus on how to estimate, with any degree of precision, the probability of a random-match, and given the great difficulty in educating the jury as to precisely what that figure means and does not mean, it might make sense to simply try to arrive at a fair way of explaining the significance of the match in a verbal, qualitative, nonquantitative, nonstatistical way."). See also Kreiling (1993).

86

Cf. United States v Fatico, 458 F. Supp. 388, aff'd, 603 F .2d 1053 (2d Cir. 1979), cert. denied, 444 U.S. 1073 (1980) (a survey of district judges revealed that their assessment of the probability of guilt associated with the "beyond a reasonable doubt" standard ranged from 76% to 90%).

87

Some commentators distinguish between the probability of a reported match (including the risk of sample mishandling or laboratory error that would produce a false positive result) and the probability of a true (but coincidental) match for a person selected at random. E.g., Koehler 1993b.

88

For cases rejecting this argument, see, e.g., United States v Chischilly, 30 F.3d 1144 (9th Cir. 1994) (citing cases); State v Weeks, 891 P.2d 891 P.2d 477 (Mont. 1995); State v Schweitzer, 533 N.W.2d 156, 160 (S.D. 1995) (reviewing cases).

89

State v Carlson, 267 N.W.2d 160 (Minn. 1978); McCormick (1992, § 210). The opinions of the Minnesota Supreme Court also posit "a real danger that the jury will use the evidence as a measure of the probability of the defendant's guilt or innocence" (State v Schwartz, 447 N.W.2d 422, 428 (Minn. 1989], quoting State v Boyd, 331 N.W.2d 480, 483 [Minn. 1983]).

90

For example, Goodman (1992) varied the frequency of the suspect's blood type in a hypothetical homicide case in which the sample of blood from the scene of the crime matched that taken from the defendant and not the victim. Although the mock jurors with frequency information were more likely to convict than those who received no frequency information, and although guilty verdicts decreased as the frequency of a random-match went from 0.001 to 0.1, frequencies of 0.001, 0.01, and 0.05. did not produce differing rates of conviction. Other research on blood-type evidence has produced similar results (Faigman and Baglioni 1988; Thompson and Schumann 1987).

91

See Kaye and Koehler 1991 (reviewing studies). Koehler and colleagues (1995) provided a brief written summary of a homicide case in which the case evidence was circumstantial and weak apart from the DNA evidence. In two studies, one with college students and a replication with jurors, respondents were assigned to one of three laboratory error-rate conditions (absent, 0.02, 0.001) and were either provided with a 1/(1 billion) probability of a random-match or given no information on the probability of a random-match. Conviction rates were influenced by the information on probability of a random-match but unaffected by the presence or level of the laboratory error-rate information. Yet conviction rates with information on probability of a random-match averaged 44% for the students (44% with and 44% without laboratory error information) and 49% for the jurors (54% with and 44% without laboratory error information), reinforcing the impression that jurors are not overwhelmed by statistical DNA evidence.

92

Examples are collected in Kaye (1993) and Koehler (1993a). See also, e.g., United States v Martinez, 3 F.2d 1191, 1194 (8th Cir. 1993) ("The second step of the DNA identification process then involves a determination of the probability that someone other than the contributor of the known sample could have contributed the unknown sample."); Greenwood v United States, 659 A.2d 825, 826 (DC Ct. App. 1995) ("The parties stipulated that DNA evidence established that the probability that Greenwood was the source of the semen found on the victim's underpants was not less than 2000 to 1."); People v Heaton, 266 III. App. 3d 469, 640 N.E.2d 630 (1994) (an expert was said to have testified that "the probability of another Caucasian . . . was 1 in 52,600"); Commonwealth v Crews, 640 A.2d 395, 400 (Pa. 1994) ("DNA analysis generally can provide only statistical probability; e.g., there is one chance in four hundred or one chance in four million that the DNA samples come from someone else.''); Taylor v State, 889 P.2d 319 (Okla. Ct. Crim. App. 1995) (Lifecodes's expert was said to have "testified that the likelihood that an African American other than Taylor contributed the DNA ... was one in 97 billion"); Taylor v Commonwealth, No. 1767-93-1, 1995 WL 80189 (Va. Ct. App. Feb. 28, 1995) (an unpublished opinion reporting that "DNA analysis of semen obtained from the victim and defendant's blood established a probability of I in 128 million that a black male other than defendant was the perpetrator").

93

As regards the transposition fallacy, such an instruction might be framed along these lines: "In evaluating the expert testimony on the DNA evidence, you were presented with a number indicating the probability that another individual drawn at random from the [specify] population would coincidentally have the same DNA profile as the [blood stain, semen stain, etc.]. That number, which assumes that no sample mishandling or laboratory error occurred, indicates how distinctive the DNA profile is. It does not by itself tell you the probability that the defendant is innocent."

94

The only study comparing reactions to separate and combined estimates found that subjects were insensitive to information on error rates when the random-match probability and the laboratory-error rate were presented separately (Koehler, Chia, and Lindsey 1995). The "evidence" in the mock case, however, was presented in the form of a single sentence unaccompanied by explanation or argument.

95

In the short run, it is appropriate to alert jurors both to the value of the statistical evidence and to its limitations. In the longer run, research should be conducted to evaluate the impact of DNA testimony on juror decision-making and the effects of alternative approaches, such as likelihood ratios or instructions in applying Bayes's theorem, on jury comprehension. Studies are needed that test reactions to the kind of DNA evidence that is presented in the courtroom, along with witness explanations, attorney arguments, and judicial instructions. Such hypotheses as the suggestion that jurors faced with the estimated laboratory-error rate and the random-match probability might average the two (Lempert 1993) or that jurors will fail to use information on laboratory-error rates cannot be evaluated in a useful way if jurors are not provided with the kind of assistance that they would receive in the relevant legal setting. Additional research on juror reactions should test the ability of jury instructions, videotaped expert explanations, and other educational efforts to facilitate appropriate interpretation of DNA evidence.

96

As discussed in Chapter 5, with match-binning, the numerator is slightly less than I because there is a very small chance that two measurements of the same band will not satisfy the match criteria (see Kaye 1995b).

97

Likelihood ratios were used in State v Klindt, 389 N.W.2d 670 (Iowa 1986) (discussed later), and are admitted routinely in parentage litigation, where they are known as the "paternity index" (see Chapter 5). E.g., Kaye 1989; Aickin and Kaye 1983; McCormick 1992, § 212. Some state statutes use them to create a presumption of paternity (Kaye 1990a,b,c). The practice of providing a paternity index has been carried over into criminal cases in which genetic parentage is used to indicate the identity of the perpetrator of an offense. E.g., State v Skipper, 228 Conn. 610, 637 A.2d 1101 (1994); Davis v State, 476 N.E.2d 127 (Ind. Ct. App. 1985); State v Weeks, 891 P.2d 477 (Mont. 1995); State v Spann, 130 N.J. 484, 617 A.2d 247 (1993): State v Jackson, 320 N.C. 452, 358 S.E.2d 679 (1987). Some of the appellate courts in some of these cases disapproved of the biostatistical presentations, but none specifically condemned the use of the likelihood ratio.

98

E.g., Evett 1991, p 201 ("Just leaving a court with a likelihood ratio does not seem enough."): cf. Fienberg 1992 (criticizing presentation of a relative likelihood function).

99

See Smith v Deppish, 807 P.2d 144 (Kan. 1991) (the state's "DNA experts informed the jury that ... there was more than a 99 percent probability that Smith was a contributor of the semen"); State v Thomas, 830 S.W.2d 546 (Mo. Ct. App. 1992) (a geneticist testified that "the likelihood that the DNA found in Marion's panties came from the defendant was higher than 99.99%"): Commonwealth v Crews, 640 A.2d 395, 402 (Pa. 1994) (an FBI examiner who at a preliminary hearing had estimated a coincidental-match probability for a VNTR match "at three of four loci" reported at trial that the match made identity "more probable than not").

100

State v Skipper, 228 Conn. 610, 637 A.2d 1101 (1994) (reasoning that this application of Bayes's theorem violated the presumption of innocence and suggesting in dictum that any use of Bayes's theorem would be impermissible); State v Hartman, 426 N.W. 2d 320 (Wis. 1988). The undisclosed use of a prior probability of one-half was standard in civil cases and first was criticized in Ellman and Kaye (1979). The courts that routinely admitted such testimony probably did not recognize the Bayesian nature of the "probability of paternity" laid before them, but courts unmistakably apprised of the foundations of these probabilities have continued to approve of them. A few courts have imposed restrictions on the practice. E.g., Commonwealth v Beausoleil, 490 N.E.2d 788 (Mass. 1986); Plemel v Walter, 735 P.2d 1209 (Or. 1987). For discussion and criticism, see Kaye (1988b, 1989).

101

Finkelstein and Fairley (1970). For LR = 1,000,000, the posterior probability approaches I for all but invisible values of the prior probability. For example, the prior probability would have to be about 1/1,000,000 or less to keep the posterior probability to less than one-half.

102

See State v Skipper, 228 Conn. 610 (1994) (stating in dictum that it would be an error to use the variable-prior-odds approach); State v Spann, 130 N.J. 484, 617 A.2d 247 (1993) (remanding for possible consideration of the use of a Bayesian graph of the probability of paternity). The Skipper opinion is criticized by many of the discussants in Allen et al. (1995).