Interpreting forensic DNA evidence on the basis of hypotheses testing.

Analysis of a mixed biological stain by means of highly polymorphic VNTR systems usually reveals a profile composed of multiple markers. If the victim and one or several suspects match the profile the evidential strength of the matches has to be very carefully analysed. It is shown that a treatment to evaluate mixed stains within the scope of a hypotheses testing approach yields a formula identical to one proposed recently by Weir und coauthors. A simple combinatorial proof of this formula is presented. Further, a special computational formula is derived for the cases where the formula of Weir turns out to be cumbersome.