Biostatistical evaluation of mixed stains with contributors of different ethnic origin

The analysis of a mixed biological stain by means of highly polymorphic VNTR systems usually reveals a profile composed of multiple alleles. If the victim and one or several suspects match the profile the evidential strength of the matches has to be very carefully analysed. The appropriate methods for the statistical analysis of DNA profiles advanced recently by Weir with coauthors and by the present authors are limited to cases where all non-tested persons involved in the analysis belong to the same ethnic group. The present paper extends the theory beyond this limitation.