The title of a New Scientist news report — “Software Says Amanda Knox’s DNA Wasn’t at Crime Scene” — suggests that a new study has excluded Knox as a killer of Meredith Kercher. Not so fast, says the Professor David Balding, the author of the study.
Balding, a statistical geneticist at University College London, has made important contributions to the statistical evaluation of forensic DNA profiles. Now he is developing an open-source program to make inferences about the contributors to low-template DNA samples — samples that have too few copies of DNA fragments to amplify reliably.
An article in the Proceedings of the National Academy of Sciences (USA) describes the program and applies it to an electropherogram the police obtained from one sample in the Knox-Sollecito case. Seeking to clarify the New Scientist report, Balding describes this finding on his website … [continued on FSSL]
Recent postings on the FSSL blog (March 27, May 25) about the appeal of Amanda Knox and Raffaele Sollecito suggested that the court’s decision not to order more DNA tests on the kitchen knife was less a manifestation of bad judicial mathematics than a judgment about the possible costs and benefits of additional low template (LT-DNA) testing as perceived by court-appointed experts. As a publication of the Royal Statistical Society noted last year, “Many questions at the extremities of LTDNA technology remain unanswered, and scientific disputes between experts are sometimes ventilated in litigation.” (Puch-Solis et al. 2012, at 85 � 60.20, discussing English Court of Appeal cases in �� 60.21 & 60. 22).
In the United States, appellate courts have yet to address the admission of LT-DNA results. The latest opinion I have seen comes from a trial court in Bronx County, New York. Remarks on People v. Garcia, 39 Misc.3d 482, 963 N.Y.S.2d 517 (N.Y. Sup. Ct. 2013), are on the FSSL blog, May 30.
Puch-Solis, Roberto, Paul Roberts, Susan Pope, and Colin Aitken 2012. Assessing the Probative Value of DNA Evidence: Guidance for Judges, Lawyers, Forensic Scientists and Expert Witnesses. London: Royal Statistical Society.