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The Probabilistic Genotyping Software STRmix: Utility and Evidence for its Validity

NCJ Number
Journal of Forensic Sciences Volume: 64 Issue: 2 Dated: 2019 Pages: 393-405
Date Published
13 pages

The principles behind STR mix are outlined in this study and include standard mathematics and modeling of peak heights and variability in those heights.


Forensic DNA interpretation is transitioning from manual interpretation based usually on binary decisionmaking toward computer based systems that model the probability of the profile given different explanations for it, termed probabilistic genotyping (PG ). Decisionmaking by laboratories to implement probability based interpretation should be based on scientific principles for validity and information that supports its utility, such as criteria to support admissibility. All PG methods generate a likelihood ratio (LR ) and require the formulation of propositions. Principles underpinning formulations of propositions include the identification of reasonably assumed contributors. Substantial data have been produced that support precision, error rate, and reliability of PG , and in particular, STR mix. A current issue is access to the code and quality processes used while coding. There are substantial data that describe the performance, strengths, and limitations of STR mix, one of the available PG software. (publisher abstract modified)

Date Published: January 1, 2019