DNA mixture interpretation principles: insights from the NIST scientific foundation review

Published

July 1, 2020

Author(s)

John Butler, Hariharan Iyer, Richard Press, Melissa Taylor, Peter Vallone, Sheila Willis

Abstract

DNA mixture interpretation has become more challenging in recent years due to several factors including submission of more touch evidence samples to aid investigations and generation of more sensitive DNA test results with new STR typing kits. This sensitivity enables recovery of DNA results from low quantities of biological material. However, the PCR signal amplification process, which provides the DNA test sensitivity, also introduces artifacts into the resulting data including stutter products as well as allele drop-out, allele drop-in, and heterozygote imbalance that occur due to stochastic effects. These artifacts combined with allele sharing among contributors make separating the contributing genotypes difficult and therefore influence uncertainty related to the both the interpretation process and associating potential contributors with the mixture. Probabilistic genotyping software programs are being implemented in many laboratories to aid evaluation of low-template DNA results either from single-source samples or trace components of mixtures.

Proceedings Title

Proceedings of the 29th International Symposium on Human Identification

Conference Dates

September 24-27, 2018

Conference Location

Phoenix, AZ, US

Pub Type

Conferences

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Keywords

forensic DNA, DNA mixture interpretation, NIST scientific foundation review

Citation

Butler, J. , Iyer, H. , Press, R. , Taylor, M. , Vallone, P. and Willis, S. (2020), DNA mixture interpretation principles: insights from the NIST scientific foundation review, Proceedings of the 29th International Symposium on Human Identification, Phoenix, AZ, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926808 (Accessed September 30, 2025)