The discussions of theory and method address the interpretation of DNA mixture in a subpopulation when two of the unknown contributors are related or when a contributor is not available for typing but his/her relative is available. The method is illustrated by using an example provided by Fukshansky and Bar (1998). In this case, the mixed stain was assumed to be contributed by three people, i.e., the victim and two unidentified assailants. According to the genotypes of the two suspects, they could not be excluded from being donors of the mixed stain. The prosecution hypothesis was that the contributors of the mixed stain were the victim and the two suspects. Seven defense hypotheses for the alleles of the mixed stain are also listed, and the likelihood ratios for these defense propositions are examined for various kinship relationships. A Windows-based computer software for calculating the likelihood ratio was developed. Because only minimal information is required for input to the software, it is less susceptible to transcriptional error. Also, the DNA mixture can be evaluated simultaneously with frequency data for various ethnic groups. This feature is useful in countries that have multiple racial groups. The findings can easily be saved to a file for cross-checking and reporting. A common mixture problem of nine loci can be assessed in 10 minutes. The software thus reduces the time needed and increases the accuracy during input for common DNA mixture problems that involve unrelated persons. 16 references