“Blame the brother”-assesment of forensic DNA evidence when alternative explanations have different likelihoods
2011 (English)In: Book of Abstracts, 2011, 196- p.Conference paper (Refereed)
In a crime case where a suspect is assumed to be the donor of a recovered stain, forensic DNA evidence presentedin terms of a likelihood ratio is a clear course as long as the set of alternative donors contains no closerelative of the suspect, since the latter has a higher likelihood than has an individual unrelated to the suspect.The state-of-art today at several laboratories is to report the likelihood ratio but with a reservation stating itslack of validity if the stain originates from a close relative. Buckleton et al  derived a so-called extendedlikelihood ratio for reporting DNA evidence values when a full sibling is present in the set of potential alternativedonors. This approach requires consideration of prior probabilities for each of the alternative donors tobe the source of the stain and may therefore be problematic to apply in practice. Here we present an alternativeway of using prior probabilities in the extended likelihood ratio when the latter is reported on an ordinal scaleof conclusions. Our example show that for a 12 STR-marker profile using the extended likelihood ratio approachwould not imply a change in the level reported compared to the ordinary likelihood ratio approach, unless theclose relative has a very high prior probability of being the donor compared to an unrelated individual. Buckleton JS, Triggs CM, Champod C., Science & Justice 46: 69-78
Place, publisher, year, edition, pages
2011. 196- p.
National CategoryNatural Sciences
IdentifiersURN: urn:nbn:se:liu:diva-70273OAI: oai:DiVA.org:liu-70273DiVA: diva2:437708
24th World Congress of the International Society for Forensic Genetics 2011