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