Abstract
In criminal investigations, forensic scientists need to evaluate DNA mixtures. The estimation of the number of contributors and evaluation of the contribution of a person of interest (POI) from these samples are challenging. In this study, we developed a new open-source software “Kongoh” for interpreting DNA mixture based on a quantitative continuous model. The model uses quantitative information of peak heights in the DNA profile and considers the effect of artifacts and allelic drop-out. By using this software, the likelihoods of 1–4 persons’ contributions are calculated, and the most optimal number of contributors is automatically determined; this differs from other open-source software. Therefore, we can eliminate the need to manually determine the number of contributors before the analysis. Kongoh also considers allele- or locus-specific effects of biological parameters based on the experimental data. We then validated Kongoh by calculating the likelihood ratio (LR) of a POI’s contribution in true contributors and non-contributors by using 2–4 person mixtures analyzed through a 15 short tandem repeat typing system. Most LR values obtained from Kongoh during true-contributor testing strongly supported the POI’s contribution even for small amounts or degraded DNA samples. Kongoh correctly rejected a false hypothesis in the non-contributor testing, generated reproducible LR values, and demonstrated higher accuracy of the estimated number of contributors than another software based on the quantitative continuous model. Therefore, Kongoh is useful in accurately interpreting DNA evidence like mixtures and small amounts or degraded DNA samples.
Highlights
In forensic casework, the DNA typing system for short tandem repeat (STR) loci is used for criminal investigations
We considered a true major contributor and a true minor contributor as person of interest (POI) in each mixture, and calculated the likelihood ratio (LR) values of each POI (Fig 3)
The LR values tended to decrease as the amount of DNA of the POI decreased
Summary
In forensic casework, the DNA typing system for short tandem repeat (STR) loci is used for criminal investigations. STR alleles of approximately 15 loci are amplified simultaneously in the polymerase chain reaction (PCR) process, and the repeated numbers are determined through the observed allelic peaks in capillary electrophoresis. New open-source software for DNA mixture interpretation individual, the sample approval allowed us to use these data for this study only. The datasets generated and/or analyzed during the current study are not publicly available owing to participant confidentiality, but will be available from the corresponding author on reasonable request after obtaining ethical approvals from the ethics committee of Kyoto University Graduate School and Faculty of Medicine (http://www.ec.med.kyotou.ac.jp/index.html)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
