#Forensics: #DNA STR MIXture takes a hit in its expanding use by FBI and other police crime labs.

Image result for cart before the horse

From DNA expert Dan Krane (thanks to Gil Sapir).

STRMix was found to be inadmissible in an important federal case ( Gissantaner ) out of the Western District of Michigan last week.  Its implications for STRMix (and the FBI’s increasing reliance on it) make this very likely to be appealed.  But, there is a potential for this to add an important new layer to things like the Daubert and Kelly-Frye standards (e.g. that tests should not be used outside of their validated range, and the relevant scientific community should not be limited to practitioners). Here is the bottom line from the court ruling inadmissibility exists in this particular case. It is telling:

“STRmix software had been in use a mere two years before its application to this case. And it had been in use by the MSP merely three months at the time of the DNA report and the conclusions reached by the MSP analysts—in simple terms, that the 7% contributor was 49 million times more likely to be Defendant than some unknown contributor.16 At that time, and even currently, there are no standards in place governing the development of PGS and its use in forensic DNA analysis.”

More articles (after the “Full Ruling) on how under validated methods are exaggerated (usually by prosecutors’ experts) when they get into criminal courts.

Full Ruling: Gissantaner – strmix inadmissible


FBI: DNA lab problems, scandals now presents new training on DNA STR stats

STRMix 2019 presentation about a “collaborative exercise.”

About csidds

Dr. Michael Bowers is a long time forensic consultant in the US and international court systems.
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2 Responses to #Forensics: #DNA STR MIXture takes a hit in its expanding use by FBI and other police crime labs.

  1. John Lentini says:

    The government can appeal, but the standard for overturning a Daubert ruling, “abuse of discretion” has not been met. The judge wrote a careful opinion, no doubt mindful of the possibility of an appeal.

  2. Brent Ostrum says:

    That’s true but the quote shown above does include a transposed conditional (that may or may not have been in the testimony). The ruling has a mix of statements about the conclusion, some of which are correct and others transposed. That suggests some misunderstanding is present. Not sure if that will matter though.

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