Interpretation of complex DNA profiles using Tippett plots

Abstract We have a developed a method to apply a likelihood ratio (LR) statistic to ambiguous DNA profiles. These are DNA profiles that exhibit the phenomena of allele drop out (missing alleles) and allele drop in (contamination from a laboratory source). We have applied the theory to complex cases and tested the robustness of the model by using Tippett plots. The robustness of a model can be determined by the measurement of two errors: the chance that a truly innocent individual will give a LR greater than one (Type I error) and the chance that a truly guilty individual will give a LR less than one (Type II error).