I believe the issues raised in this petition are a matter of grave public concern.  For this reason, I am trying to do the best I can to communicate this issue to the public and the legal community.

  • I have been working on a writ of habeas corpus involving DNA evidence

  • There are new guidelines for interpretation of complex DNA mixtures

  • State prisoners can challenge their convictions under Penal Code § 1473

What is the issue?

In January 2010, the Scientific Working Group on DNA Analysis Methods, aka “SWGDAM” published a new set of interpretation guidelines for Complex DNA Mixture Samples.  The guidelines did not affect DNA testing results, but rather the way in which DNA forensic scientists interpreted those results and how they compared those results to known suspects.

The reason SWGDAM changed their guidelines was because the old method for interpreting Complex Mixture DNA had been found to have the potential to make false identifications of suspects and to overestimate the statistical calculation associated with an identification of a suspect.  

For example, prior to 2010, a DNA analyst following the old guidelines may have compared a suspect to a complex DNA mixture of 5 different individuals and concluded that a suspect was a potential contributor to that mixture.  She may also have concluded that the statistical frequency associated with this inclusion (aka the “combined probability of inclusion” or “CPI”) was merely 1 in 450.  

For background, the CPI statistic asks the question; what are the odds that a person chosen at random from the population would be included, just by chance, as a contributor to a DNA sample.  A statistic of 1 in 450 tells the jury that only 1 out of every 450 people in the population will be included at random.

Now, under the new guidelines, it is entirely possible that the same DNA analyst can no longer conclude whether or not that same person is a contributor to the mixture.  Also, the same analyst may also say that assigning a CPI statistic to that person is inappropriate and overstated.

The reason that this hypothetical analyst has changed her opinion is because her first opinion has been found to have the very real potential of being wrong; both on the inclusion of the suspect and the statistical calculation associated with the suspect.  This means thousands of people could have been falsely identified under the old method and wrongfully convicted.

What does this mean?

Under state law (specifically Penal Code § 1473), state prisoners can challenge their convictions when “false evidence” was used against them at their trial.  In 2015, a new law went into effect defining “false evidence.”  It stated that false evidence is “opinions of experts that have either been repudiated by the expert who originally provided the opinion at a hearing or trial or that have been undermined by later scientific research or technological advances.”

In summary, current state prisoners whose cases involved complex DNA mixture samples need to have their cases reviewed, ASAP.

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