Forensic interpretation of haploid DNA mixtures

Abstract

The mathematical concept previously introduced for the forensic interpretation of DNA mixtures using non-associated genetic markers has been adapted to the assessment of haplotypes. Such calculus is required, for example, when mitochondrial or Y-chromosomal markers are used in forensics. Two approaches exist to its practical computational implementation, involving either the inclusion–exclusion principle of probability theory or a recursion in the number of unknown contributors invoked. The former approach scales better in cases of practically relevant complexity and for sufficiently diverse markers. Simulation based upon the Y-chromosomal Haplotype Reference Database suggests that the exclusion chance of a non-contributor varies between 95% in the case of two contributors to the trace, and 70% for five contributors. These estimates are however likely to be conservative since only haplotypes known to occur in YHRD have been involved in the simulations.