Nationwide, problems with lab interpretation of complex DNA mixtures persist.

I’ve been working on a writ of habeas corpus involving complex mixture DNA samples.  I have written about this several times.  In this entry I would like to emphasis that this is not just a local San Diego issue, but rather an issue of national concern.

For background, the issue at hand is a change in the interpretation methods for Complex Mixture DNA samples.  Essentially, interpretations of these complex mixtures that once deemed some suspects as inclusions, may now render those inclusions invalid.  In turn, this means many people now in prison could have been falsely identified and wrongfully convicted.

Three examples of crime labs outside of California illustrate the widespread problem that needs to be addressed on a national level.

  • District of Columbia Crime Lab, Washington D.C.

    In 2015, ANAB, a national accrediting body for forensic crime labs, conducted an audit on the District of Columbia Crime Lab.  In their audit, they found the DC crime lab violated the SWGDAM guidelines (the same ones at issue here in San Diego with the SDPD crime lab)  in their interpretation of complex mixtures.  ANAB revoked their DC Crime Lab’s accreditation and they are no longer allowed to do casework on complex mixtures.

  • Austin PD Crime Lab, Texas

    In 2016, the Texas Forensic Science Commission completed an audit of forensic DNA cases analyzed by the Austin PD Forensic Science Division’s DNA Section.  The audit found that significant statistical changes to DNA interpretations were attributed to the fact that the evidence in these cases had been originally analyzed before the laboratories made certain important revisions to their mixture interpretation protocols to comply with recommendations made by the Scientific Working Group on DNA Analysis Methods (SWGDAM) in 2010.   In other words, the audit found that the over estimates of CPI statistics were directly correlated with analyses of the samples using the old, out-dated, guidelines similarly used by the SDPD Crime Lab.  The Commission ultimately recommended temporarily suspending Austin Crime Lab’s ability to do case work on DNA mixtures.

  • Broward County Sheriff’s Office Crime Lab, Florida

    In 2015 and 2016 the American Society of Crime Laboratory Directors, Laboratory Accreditation Board (aka “ASCLD-LAB”) disciplined the Broward County Sheriff’s Department for “irregularities” in their mixture interpretation methods. Among other issues, they failed to follow the 2010 SWGDAM guidelines.  In its technical review, ASCLAD-LAB stated that the method used was “flawed.”

What does it mean?

These examples involve complex mixture interpretation methods that are substantially similar to those that the SDPD was using prior to April 1, 2011.  They highlight that the science community has undergone a fundamental change in DNA mixture interpretation science, highlighted by the change in SWGDAM guidelines in 2010.  This scientific change has shed light on the very real possibility of wrongful convictions nationwide.

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