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Advancing Probabilistic Approaches to Interpreting Low-template DNA Profiles and Mixtures: Developing Theory, Implementing Practice

NCJ Number
Date Published
July 2018
57 pages
This is the report on a project that assessed the performance of a probabilistic approach applied to "complex" DNA samples, which include samples that contain low levels of DNA and/or mixtures of DNA from multiple individuals; and it also improved and extended "Lab Retriever," an existing freely available program that can assist in understanding the weight of evidence yielded from these complex DNA profiles.

Overall, this project has increased knowledge regarding the interpretation of complex DNA profiles and added new features to a freely available software program that continues to assist forensic DNA analysts in accurately and efficiently assessing the weight of such evidence. Specifically, this project produced a set of low-template DNA mixtures. This dataset has been used in other parts of the project and will be made available to the community for evaluation of various statistical approaches. The project also evaluated the performance of estimates of drop-out probabilities in mixed samples. Further, it computed and evaluated results of likelihood ratios (LRs) for simulated complex mixtures of two, three, four, and five contributors. In addition, it evaluated the role of stutter in mixture interpretation. The report notes that the Lab Retriever software has a number of attractive features, including an open source platform, a basis in published algorithms, flexibility in terms of the hypotheses that can be considered, nearly instantaneous run-time, and a friendly graphic user interface.

Date Published: July 1, 2018