Encoding of low-quality DNA profiles as genotype probability matrices for improved profile comparisons, relatedness evaluation and database searches

摘要

Many DNA profiles recovered from crime scene samples are of a quality thatdoes not allow them to be searched against, nor entered into, databases. Wepropose a method for the comparison of profiles arising from two DNA samples,one or both of which can have multiple donors and be affected by low DNAtemplate or degraded DNA. We compute likelihood ratios to evaluate thehypothesis that the two samples have a common DNA donor, and hypothesesspecifying the relatedness of two donors. Our method uses a probabilitydistribution for the genotype of the donor of interest in each sample. Thisdistribution can be obtained from a statistical model, or we can exploit theability of trained human experts to assess genotype probabilities, thusextracting much information that would be discarded by standard interpretationrules. Our method is compatible with established methods in simple settings,but is more widely applicable and can make better use of information than manycurrent methods for the analysis of mixed-source, low-template DNA profiles. Itcan accommodate uncertainty arising from relatedness instead of or in additionto uncertainty arising from noisy genotyping. We describe a computer programGPMDNA, available under an open source license, to calculate LRs using themethod presented in this paper.