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You are here: Home / Cases / DNA-only evidence not sufficient in CT case

DNA-only evidence not sufficient in CT case

August 14, 2021 //  by Sarah Olson//  Leave a Comment

Defenders may be interested to read the Connecticut Supreme Court decision, State v. Andre Dawson (2021) in which the Court found that the state failed to present sufficient evidence of constructive possession where the defendant could not be excluded from a DNA mixture containing a partial profile found on a firearm.

In the case, a DNA profile was developed from swabs containing about 70 picograms of DNA. The DNA analyst testified that 1000 picograms is the ideal amount for DNA analysis. She obtained results at 7 of 15 loci tested. The DNA was a mixture of two or more individuals. The analyst excluded other individuals who were in proximity of the firearm in a public space. The defendant could not be eliminated as a contributor and the expected frequency of individuals who could not be eliminated as a contributor to the DNA profile was one in 1.5 million, according to the analyst’s testimony.

The court considered multiple factors related to the location of the firearm and access to it, but determined that even with the DNA evidence, the jury could not reasonably have concluded beyond a reasonable doubt that the defendant had knowledge of the gun, and with intent, exercised dominion or control over it.

The court was troubled by the lack of conclusiveness regarding the DNA evidence for several reasons, which are common in partial profile cases:

  • The analyst was not able to determine how the DNA ended up on the gun – whether primary or secondary transfer or aerosolization
  • The analyst was not able to determine when the DNA was deposited on the gun
  • The DNA sample was a mixture, meaning at least one other person’s DNA was on the gun
  • Exclusion of the other individuals as contributors to the mixture did not mean their DNA wasn’t on the gun, it just wasn’t detected in that sample
  • Additional individuals present at the scene were not DNA tested
  • The analyst testified that she could not definitively say that the DNA profile developed was that of the defendant; she could determine only that he could not be excluded as a contributor

The court found “there were simply too many unknowns for the jury to find beyond a reasonable doubt that the defendant had even touched the gun, much less that he was aware of its presence near where he was seated on the night in question and intended to exercise dominion or control over it.”

Attorneys who are trying “touch DNA” cases should consider the limitations to “touch DNA” that are addressed in this opinion. In many cases, bringing out the relevant factors mentioned above can illustrate the limited probative value of a partial profile originating from a DNA mixture.

As always, I’m happy to consult with attorneys on court-appointed cases involving scientific evidence. I can help with cross-examination questions that illustrate the limitations of “touch DNA” evidence. Please email me (Sarah.R.Olson@nccourts.org) if I can be of assistance.

Category: CasesForensic Discipline: DNA

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