title: Evaluating forensic biology results given source level propositions.
abstract: The evaluation of forensic evidence can occur at any level within the hierarchy of propositions depending on the question being asked and the amount and type of information that is taken into account within the evaluation. Commonly DNA evidence is reported given propositions that deal with the sub-source level in the hierarchy, which deals only with the possibility that a nominated individual is a source of DNA in a trace (or contributor to the DNA in the case of a mixed DNA trace). We explore the use of information obtained from examinations, presumptive and discriminating tests for body fluids, DNA concentrations and some case circumstances within a Bayesian network in order to provide assistance to the Courts that have to consider propositions at source level. We use a scenario in which the presence of blood is of interest as an exemplar and consider how DNA profiling results and the potential for laboratory error can be taken into account. We finish with examples of how the results of these reports could be presented in court using either numerical values or verbal descriptions of the results.
authors.affiliation: Forensic Science South Australia, 21 Divett Place, Adelaide, SA 5000, Australia; School of Biological Sciences, Flinders University, GPO Box 2100 Adelaide SA, Australia 5001. Electronic address: Duncan.Taylor@sa.gov.au.
authors.forename: Duncan
authors.initials: D
authors.lastname: Taylor
authors.affiliation: Forensic Science South Australia, 21 Divett Place, Adelaide, SA 5000, Australia; School of Biological Sciences, Flinders University, GPO Box 2100 Adelaide SA, Australia 5001.
authors.forename: Damien
authors.initials: D
authors.lastname: Abarno
authors.affiliation: School of Criminal Justice, University of Lausanne & Fondation pour la formation continue universitaire lausannoise, Lausanne, Dorigny, Switzerland.
authors.forename: Tacha
authors.initials: T
authors.lastname: Hicks
authors.affiliation: School of Criminal Justice, University of Lausanne, Lausanne, Dorigny, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Champod
mesh_terms: D001499:Bayes Theorem; D001826:Body Fluids / Q000737:chemistry; D004247:DNA / Q000032:analysis / Q000235:genetics; D016172:DNA Fingerprinting / Q000379:methods*; D044707:Forensic Sciences / Q000379:methods*; D006801:Humans; D016013:Likelihood Functions
chemical_list: D004247:DNA
keywords: Bayesian networks; Body fluid; Hierarchy of propositions; Likelihood ratio; Presumptive tests; STRmix; Source level propositions