Forensic population genetics – original research| Volume 16, P165-171, May 2015

Testing likelihood ratios produced from complex DNA profiles

Published:January 17, 2015DOI:


      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.


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        • Taylor D.
        • Bright J.-A.
        • Buckleton J.
        The interpretation of single source and mixed DNA profiles.
        Forensic Sci. Int. Genet. 2013; 7: 516-528
        • Forensim H.H.
        An open-source initiative for the evaluation of statistical methods in forensic genetics.
        Forensic Sci. Int. Genet. 2011; 5: 265-268
        • Lohmueller K.
        • Rudin N.
        Calculating the weight of evidence in low-template forensic DNA casework.
        J. Forensic Sci. 2013; 58: 234-259
        • Steele C.D.
        • Balding D.J.
        Statistical Evaluation of Forensic DNA Profile Evidence.
        Ann. Rev. Stat. Appl. 2014; 1: 361-384
        • Puch-Solis R.
        • Rodgers L.
        • Mazumder A.
        • Pope S.
        • Evett I.
        • Curran J.
        • et al.
        Evaluating forensic DNA profiles using peak heights, allowing for multiple donors, allelic dropout and stutters.
        Forensic Sci. Int. Genet. 2013; 7: 555-563
        • Balding D.J.
        • Buckleton J.
        Interpreting low template DNA profiles.
        Forensic Sci. Int. Genet. 2009; 4: 1-10
        • Perlin M.W.
        • Legler M.M.
        • Spencer C.E.
        • Smith J.L.
        • Allan W.P.
        • Belrose J.L.
        • et al.
        Validating TrueAllele® DNA mixture interpretation.
        J. Forensic Sci. 2011; 56: 1430-1447
        • Cowell R.G.
        • Lauritzen S.L.
        • Mortera J.
        Probabilistic modelling for DNA mixture analysis.
        Forensic Sci. Int. Genet. 2008; 1 (Supplement series): 640-642
        • Gill P.
        • Haned H.
        A new methodological framework to interpret complex DNA profiles using likelihood ratios.
        Forensic Sci. Int. Genet. 2013; 7: 251-263
        • Schneider P.M.
        DNA databases for offender identification in Europe - the need for technical, legal and political harmonisation.
        in: The Second European Symposium on Human Identification, Innsbruck, Austria1998
        • Dørum G.
        • Bleka Ø.
        • Gill P.
        • Haned H.
        • Snipen L.
        • Sæbø S.
        • et al.
        Exact computation of the distribution of likelihood ratios with forensic applications.
        Forensic Sci. Int. Genet. 2014; 9: 93-101
        • Taylor D.A.
        • Bright J.-A.
        • Buckleton J.S.
        The ‘factor of two’ issue in mixed DNA profiles.
        J. Theor. Biol. 2014; 363: 300-306
        • Good I.J.
        Probability and the Weighing of Evidence.
        Charles Griffin & Company Limited, London1950
        • Evett I.W.
        • Lambert J.A.
        • Buckleton J.S.
        • Weir B.S.
        Statistical analysis of a large file of STR profiles of British Caucasians to support forensic casework.
        Int. J. Legal Med. 1996; 109: 173-177
        • Prieto L.
        • Haned H.
        • Mosquera A.
        • Crespillo M.
        • Alemañ M.
        • Aler M.
        • et al.
        Euroforgen-NoE collaborative exercise on LRmix to demonstrate standardization of the interpretation of complex DNA profiles.
        Forensic Sci. Int. Genet. 2014; 9: 47-54
        • Taylor D.
        Using continuous DNA interpretation methods to revisit likelihood ratio behaviour.
        Forensic Sci. Int. Genet. 2014; 11: 144-153
        • Walsh S.J.
        • Buckleton J.S.
        Autosomal microsatellite allele frequencies for a nationwide dataset from the Australian Caucasian sub-population.
        Forensic Sci. Int. Genet. 2007; 168: e47-e50
        • Balding D.J.
        • Nichols R.A.
        DNA profile match probability calculation: how to allow for population stratification, relatedness, database selection and single bands.
        Forensic Sci. Int. Genet. 1994; 64: 125-140