L.A. Times Statistics Expert Says L.A. Times “Mischaracterized” Crucial Statistic in DNA “Cold Hit” Article
A statistics expert cited by the L.A. Times has now publicly claimed that the paper “mischaracterized” a central statistic in a Page One article on DNA, statistics, and cold hits.
Prof. David Kaye was recently described by L.A. Times reporters Jason Felch and Maura Dolan as “an expert on science and the law at Arizona State University and former member of a national committee that studied forensic DNA.”
Prof. Kaye’s article is scheduled to appear in the journal “Law, Probability, and Risk” in September 2008. Alert readers will recognize the error cited by Prof. Kaye as one that I have repeatedly complained about on this blog. Here’s Prof. Kaye:
Diana Sylvester, a “22-year-old San Francisco nurse had been sexually assaulted and stabbed in the heart” in her San Francisco apartment over thirty years ago. A DNA database match from a highly degraded semen sample led investigators to “John Puckett, an obese, wheelchair-bound 70-year-old with a history of rape.” The jury heard that the random-match probability for the match at five or so loci was about 1 in 1.1 million. It did not learn that the California database had 338,000 profiles in it, making np almost 1 in 3 — a number that would render the match almost worthless to the prosecution (and that the reporters mischaracterized as “the probability that the database search had hit upon an innocent person”).
(All emphasis in this post is mine.)
Yes, they did indeed mischaracterize the probability, as I have been arguing for months.
I’ll send a link to this post, and Prof. Kaye’s article, to reporter Felch and to Jamie Gold. They have dismissed my complaints on this issue in the past. But it seems to me that they have to pay attention, now that an expert they have cited has stated in an academic article that the article “mischaracterized” the central statistic in the article.
P.S. You shouldn’t misread Prof. Kaye’s phrasing to indicate that he believes the match was indeed “almost worthless to the prosecution.” Further details, set forth in the extended entry, will dispel that notion. Those details are of interest mainly to those intensely interested in this topic. But I know there are a few of you among the regular readers here.