Highlights
- •Complex DNA profiles encoded as probability distributions for the genotypes of one or more contributors.
- •Formulas for calculating likelihood ratios for comparisons of genotype probability matrices.
- •Compare a reference profile with a complex profile or two complex profiles.
- •Database searches performed rapidly with uncertain genotypes both as query and included in the database.
- •Open-source software available.
Abstract
Many DNA profiles recovered from crime scene samples are of a quality that does not
allow them to be searched against, nor entered into, databases. We propose 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 DNA template or degraded DNA. We compute
likelihood ratios to evaluate the hypothesis that the two samples have a common DNA
donor, and hypotheses specifying the relatedness of two donors. Our method uses a
probability distribution for the genotype of the donor of interest in each sample.
This distribution can be obtained from a statistical model, or we can exploit the
ability of trained human experts to assess genotype probabilities, thus extracting
much information that would be discarded by standard interpretation rules. Our method
is compatible with established methods in simple settings, but is more widely applicable
and can make better use of information than many current methods for the analysis
of mixed-source, low-template DNA profiles. It can accommodate uncertainty arising
from relatedness instead of or in addition to uncertainty arising from noisy genotyping.
We describe a computer program GPMDNA, available under an open source licence, to
calculate LRs using the method presented in this paper.
Keywords
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Article info
Publication history
Published online: September 21, 2016
Accepted:
September 2,
2016
Received in revised form:
July 31,
2016
Received:
January 17,
2016
Identification
Copyright
© 2016 Elsevier Ireland Ltd. All rights reserved.
