database of DNA profiles.pdf

Biometrika (2006), 93, 3, pp. 525–536 ? 2006 Biometrika Trust Printed in Great Britain Forensic identification of relatives of individuals included in a database of DNA profiles B? DAVID CAVALLINI ??? FABIO CORRADI Department of Statistics, University of Florence, 50134 Florence, Italy cavallin@ds.unifi.it corradi@ds.unifi.it S?????? In this paper we evaluate the characteristics observed both on a crime sample and on individuals included in a database to assess the probability of alternative hypotheses concerning identification. The problem is first addressed by considering a generic charac- teristic and we demonstrate the problem via a computationally efficient Bayesian network. Then we turn our attention to a heritable ??? trait to show how to evaluate the hypotheses that some individuals, genetically related to the members of the database, are the donors of the crime sample. Then the network is extended to cope with many loci. Applications of the method are provided as well as details of computational requirements. Some key words: Bayesian network; Database of ??? profiles; Forensic identification; Search on a database. 1. I??????????? In this paper we consider the forensic identification problem arising when a crime sample is found but there is no clue about its origin and a search in a database is a real possibility. In the case where only non-heritable characteristics are concerned, or if heritability is not exploited, Dawid (1994) and Dawid Mortera (1996) found computationally simple solutions to cases arising in a database search involving one or more matches, imperfect evidence and different observation schemes. Simplicity was achieved mainly because all the individuals considered in the evaluation of hypotheses were observed, so that, for those not matching the crime sample, the posterior probability of identification was zero or expressed by formulae depending on laboratory error parameters. Even within this simplified setting the database search problem