Balding & You - Forensic Science Int'l Genetics - Feb 2019

A comparison of software for the evaluation of complex DNA profiles

Here, Professor David Balding and MIG student, Yupei You compare two open-source programs for the evaluation of evidential weight arising from complex DNA profiles recovered in a crime investigation. Here, “complex” means one or more of: low-template, degraded and mixed-source. Although software for complex DNA profile analysis has made great strides in recent years, the ability of courts to effectively scrutinise and challenge the reliability of the resulting evidence remains problematic. One key step is to compare different software on the same evidence, but there are currently few published comparisons in part because of the problems posed by restricted access to commercial software. We present here an extensive comparison between two open-source software, LikeLTD and EuroForMix. We find that despite different modelling assumptions the two programs generate similar results. The differences that we do identify can inform future improvements and can provide a benchmark for acceptable discrepancies between alternative programs.

You Y. & Balding D. A comparison of software for the evaluation of complex DNA profiles. Forensic Science International Genetics. DOI: https://doi.org/10.1016/j.fsigen.2019.02.014

Highlights
*We compared two software in computing LRs for complex DNA profiles.
*Overall results from likeTLD and EuroForMix were similar.
*LikeLTD returned slightly better result than EuroForMix but required longer runtime.
*Dropin models were necessary for likeLTD and EuroForMix.
*Double- and Over-Stutter models in likeLTD provided a small advantage.

ROC curveFigure 6 (from article). Receiver Operating Characteristic (ROC) curves, plotting the false positive rate (x axis) against the true positive rate (y axis) as the threshold varies for both detection threshold (T) = 50 (dashed curves) and T = 20 (solid curves). All two- and three-contributor mixture analyses are included. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article)

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David Balding

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