title: Results of an inter and intra laboratory exercise on the assessment of complex autosomal DNA profiles.
abstract: The interpretation of complex DNA profiles may differ between laboratories and reporting officers, which can lead to discrepancies in the final reports. In this study, we assessed the intra and inter laboratory variation in DNA mixture interpretation for three European ISO17025-accredited laboratories. To this aim, 26 reporting officers analyzed five sets of DNA profiles. Three main aspects were considered: 1) whether the mixed DNA profiles met the criteria for comparison to a reference profile, 2) the actual result of the comparison between references and DNA profiling data and 3) whether the weight of the DNA evidence could be assessed. Similarity in answers depended mostly on the complexity of the tasks. This study showed less variation within laboratories than between laboratories which could be the result of differences between internal laboratory guidelines and methods and tools available. Results show the profile types for which the three laboratories report differently, which informs indirectly on the complexity threshold the laboratories employ. Largest differences between laboratories were caused by the methods available to assess the weight of the DNA evidence. This exercise aids in training forensic scientists, refining laboratory guidelines and explaining differences between laboratories in court. Undertaking more collaborative exercises in future may stimulate dialog and consensus regarding interpretation. For training purposes, DNA profiles of the mixed stains and questioned references are made available.
authors.affiliation: Division of Biological Traces, Netherlands Forensic Institute, P.O. Box 24044, 2490AA, The Hague, The Netherlands. Electronic address: c.benschop@nfi.minvenj.nl.
authors.forename: Corina C G
authors.initials: CCG
authors.lastname: Benschop
authors.affiliation: Forensic Science Ireland, Garda Headquarters, Phoenix Park, D08 HN3X, Dublin, Ireland. Electronic address: EConnolly@fsl.gov.ie.
authors.forename: Edward
authors.initials: E
authors.lastname: Connolly
authors.affiliation: Biology Section, Swedish National Forensic Centre, Linköping, Sweden; Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden. Electronic address: ricky.ansell@polisen.se.
authors.forename: Ricky
authors.initials: R
authors.lastname: Ansell
authors.affiliation: Division of Biological Traces, Netherlands Forensic Institute, P.O. Box 24044, 2490AA, The Hague, The Netherlands. Electronic address: b.kokshoorn@nfi.minvenj.nl.
authors.forename: Bas
authors.initials: B
authors.lastname: Kokshoorn
mesh_terms: D016172:DNA Fingerprinting / Q000592:standards*; D005060:Europe; D006801:Humans; D007753:Laboratories / Q000592:standards*; D018895:Microsatellite Repeats; D011786:Quality Control
keywords: Autosomal STRs; Collaborative exercise; DNA mixture interpretation; Forensic science; Weight of evidence