Testing likelihood ratios produced from complex DNA profiles

Duncan Taylor, John Buckleton, Ian Evett

    Research output: Contribution to journalArticlepeer-review

    27 Citations (Scopus)


    The performance of any model used to analyse DNA profile evidence should be tested using simulation, large scale validation studies based on ground-truth cases, or alignment with trends predicted by theory. We investigate a number of diagnostics to assess the performance of the model using Hd true tests. Of particular focus in this work is the proportion of comparisons to non-contributors that yield a likelihood ratio (LR) higher than or equal to the likelihood ratio of a known contributor (LRPOI), designated as p, and the average LR for Hd true tests. Theory predicts that p should always be less than or equal to 1/LRPOI and hence the observation of this in any particular case is of limited use. A better diagnostic is the average LR for Hd true which should be near to 1. We test the performance of a continuous interpretation model on nine DNA profiles of varying quality and complexity and verify the theoretical expectations.

    Original languageEnglish
    Pages (from-to)165-171
    Number of pages7
    JournalForensic Science International: Genetics
    Publication statusPublished - May 2015


    • DNA profile interpretation
    • Likelihood ratios
    • Mixtures
    • Performance tests


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