The effect of varying the number of contributors in the prosecution and alternate propositions (Accepted Manuscript) John S. Buckleton Jo-Anne Bright Kevin Cheng Hannah Kelly Duncan Taylor 10.26091/ESRNZ.12227546.v1 https://research.esr.cri.nz/articles/journal_contribution/The_effect_of_varying_the_number_of_contributors_in_the_prosecution_and_alternate_propositions_Accepted_Manuscript_/12227546 Using a simplified model, we examine the effect of varying the number of contributors in the prosecution and alternate propositions for a number of simulated examples. <p>We compare the Slooten and Caliebe [1] solution, with several existing practices. Our own experience is that most laboratories, and ourselves, assign the number of contributors, <i>N</i> = <i>n</i>, by allele count and a manual examination of peak heights. The <i>LR<sub>n</sub></i> for one or a very few values is calculated and typically one of these is presented, usually the most conservative. This gives an acceptable approximation.</p> <p>Reassessing the number of contributors if <i>LR</i> = 0 and adding one to <i>N</i> under both <i>H<sub>p</sub></i> and <i>H<sub>a</sub></i> to “fit” the POI may lead to a substantial overstatement of the <i>LR</i>. </p> <p>A more reasonable option is to allow optimisation of the assignment under <i>H<sub>p</sub></i> and <i>H<sub>a</sub></i> separately. </p> <p>We show that an additional contributor explained the single locus profile better when This is pleasingly in line with current interpretation approaches.</p> <p>Collectively these trials, and the solid theoretical development, suggest that implementation of the Slooten and Caliebe approach is optimal.</p> 2020-05-01 00:05:22 DNA Mixture interpretation Number of Contributors Slooten and Caliebe Forensic Biology Genetics