New publication - The reliability and reporting of DNA match strength for uncertain genotype evidence.

“Handprints in Morning Dew” Produced DNA Mixtures Leading to First-Degree Murder Convictions

Case summary

Joseph John was shot and later died from his injuries. Investigators followed footprints and found two handprints on a fence post where morning dew had been disturbed. The state lab found DNA mixtures in both handprints, but could not perform statistical analysis due to the nature of the DNA data. TrueAllele® re-interpretation separated the mixture data into genotypes and produced match statistics in the millions linking both defendants to the evidence. TrueAllele results were presented at trial, and a jury convicted both defendants of first-degree murder, which carried a mandatory life sentence without parole.

What the lab report said

  • The lab found mixtures in the handprint swabs, but could not perform statistical analysis due to the nature of the DNA data. When lab interpretation is limited, TrueAllele mixture interpretation can turn “No statistical DNA results” into “Supporting DNA information”.

What was submitted

  • The lab’s electronic DNA data files from the fence-post handprint swabs (no re-testing of physical evidence items).

What changed after TrueAllele interpretation

  • TrueAllele separated the mixture data into genotypes.
  • TrueAllele produced match statistics in the millions connecting the handprint mixtures to both defendants.

Outcome

  • TrueAllele results were presented at trial, and a jury convicted both defendants of first-degree murder, which carried a mandatory life sentence without parole.

Case Takeaways

If you have “touch” DNA evidence from surfaces (fence, railing, window, gate) and the lab cannot interpret the mixtures:

  1. Request a TrueAllele screening of the key items, especially in a homicide.
  2. If the lab interpretation is limited, that’s a strong reason to screen the same lab data.

For more information on what to request from the lab, see the Sending Cases for TrueAllele Processing page.

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We don’t retest physical evidence items. We interpret the electronic DNA data a lab already generated.