Determination of the possible number of genotypes which can contribute to DNA mixtures: Non-computer assisted deconvolution should not be attempted for greater than two person mixtures.

When DNA profiles contain a mixture of contributors (N), the maximum number of alleles observed at any locus is 2 N with the number of alleles varying between 1 and 2 N. The number of possible combinations of the genotypes of the N contributors increases as N increases. The number of possible combinations of genotypes that may occur among the N contributors can be enumerated using the mathematical concept of ordered partitions. Thus the number of possible genotype combinations which can exist at an STR locus in a DNA sample having N contributors and L observed alleles at the locus can be calculated. Development of the calculation and the resulting number of possible combinations which exist for N ≤ 8 contributors is presented. The results for ≥ three contributors indicate that deconvolution of contributing genotypes using manual methods is precluded except in circumstances where a clear major contributor can identified.