Statistics plays an important role in evaluating the evidential weight of forensic DNA. In this paper, general statistical principles for forensic DNA analysis are presented. We introduce the theory and methods for the statistical assessment in kinship determination and DNA mixture evaluation. In particular, analytical formulas for testing for biological relationship among three individuals and for assessing the DNA mixture evidence in the case of multiple subdivided ethnic groups are developed. Two user-friendly computer programs are demonstrated to exhibit their wide applicability in tackling with complex kinship/paternity and mixture problems. The EasyDNA program can solve a complicated paternity case in 1 min.