The tainted atmosphere surrounding forensic science in general and specifically in regards to the devastating FBI faux pas from their elite hair people is still bouncing around the media-verse. With that still happening, the FBI now says their DNA population calculations of Random Match Probabilities have been off since 1999.. RMP; this is a bit dated but gives a decent overview. The NIST page on RMP definitions has been deleted. NIST verifies methods and standardizes DNA protocols for law enforcement crime labs. Here is a summary of various reports from a search of its website. The phrase they use is called Probabilistic Genotyping.
Someone at the FBI is gritting their teeth and taking the high-road about this, but the fall-out cannot be minimized, regardless of what they say about its having a “minimal effect” on judicial proceedings involving this biological evidence.
I will assume that their recalculating of cases (if they can even track down them all ) will be a reduction of probability stats leaving the RMPs still at very low chance of mismatching.
The defense bar will take a jaundice view about that. In fact, they already have.
Spencer Hsu’s Washington Post article starts with this:
March 29, 2014 10:03pm
The FBI has notified crime labs across the country that it has discovered errors in data used by forensic scientists in thousands of cases to calculate the chances that DNA found at a crime scene matches a particular person, several people familiar with the issue said.
The bureau has said it believes the errors, which extend to 1999, are unlikely to result in dramatic changes that would affect cases. It has submitted the research findings to support that conclusion for publication in the July issue of the Journal of Forensic Sciences, the officials said.
But crime labs and lawyers said they want to know more about the problem before conceding it would not make much difference in any given case.
What really sticks in my mind, is that the FBI people (and an inspection company composed of ex-FBI DNA analysts) accused the Washington DC independent crime lab director, Max Houck of using incorrect DNA statistics in forcing him to resign and others to be fired last month. That is here and here and here.
The Omaha World Herald reposted:
“The public puts so much faith in DNA testing that it makes it especially important to make those the best estimates possible,” said Wright State University professor of statistics Daniel Krane, an expert whose work has been cited by defense attorneys. “There is no excuse for a systematic error to many thousands of calculations in such a context.”