title: Decision analysis for the genotype designation in low-template-DNA profiles.
abstract: What genotype should the scientist specify for conducting a database search to try to find the source of a low-template-DNA (lt-DNA) trace? When the scientist answers this question, he or she makes a decision. Here, we approach this decision problem from a normative point of view by defining a decision-theoretic framework for answering this question for one locus. This framework combines the probability distribution describing the uncertainty over the trace's donor's possible genotypes with a loss function describing the scientist's preferences concerning false exclusions and false inclusions that may result from the database search. According to this approach, the scientist should choose the genotype designation that minimizes the expected loss. To illustrate the results produced by this approach, we apply it to two hypothetical cases: (1) the case of observing one peak for allele xi on a single electropherogram, and (2) the case of observing one peak for allele xi on one replicate, and a pair of peaks for alleles xi and xj, i ≠ j, on a second replicate. Given that the probabilities of allele drop-out are defined as functions of the observed peak heights, the threshold values marking the turning points when the scientist should switch from one designation to another are derived in terms of the observed peak heights. For each case, sensitivity analyses show the impact of the model's parameters on these threshold values. The results support the conclusion that the procedure should not focus on a single threshold value for making this decision for all alleles, all loci and in all laboratories.
authors: University of Lausanne, Ecole des Sciences Criminelles, Institut de Police Scientifique, le Batochime, 1015 Lausanne, Switzerland. Electronic address: simone.gittelson@unil.ch.
authors: S
authors: S
authors: Gittelson
authors: University of Lausanne, Ecole des Sciences Criminelles, Institut de Police Scientifique, le Batochime, 1015 Lausanne, Switzerland.
authors: A
authors: A
authors: Biedermann
authors: University Ca' Foscari, Dipartimento di Economia, San Giobbe, Cannaregio 873, 30121 Venice, Italy.
authors: S
authors: S
authors: Bozza
authors: University of Lausanne, Ecole des Sciences Criminelles, Institut de Police Scientifique, le Batochime, 1015 Lausanne, Switzerland.
authors: F
authors: F
authors: Taroni
mesh_terms: D000483:Alleles; D001499:Bayes Theorem; D004247:DNA / Q000032:analysis*; D016172:DNA Fingerprinting; D003661:Decision Support Techniques; D005838:Genotype; D006801:Humans; D008957:Models, Genetic
chemical_list: D004247:DNA
keywords: Bayesian decision theory; Influence diagram; Low-level-DNA threshold