The effect of varying the number of contributors in the prosecution and alternate propositions (Accepted Manuscript)

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_n</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_p</i> and <i>H_a</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_p</i> and <i>H_a</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>