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Solving major crime from minor contributors: A case report using TrueAllele® Casework
M. Legler, Z. Shawhan, J. Naylor, P. Berry, "Solving major crime from minor contributors: A case report using TrueAllele® Casework", Promega's Thirty Fourth International Symposium on Human Identification, Denver, CO, 20-Sep-2023.
On Thursday August 9th, 2018 Detective Hayes was dispatched to the scene of a home invasion. Upon arrival, a male victim was observed covered in blood laying in a ditch. They immediately notified an ambulance service. When the detective entered the residence, a female victim was discovered with lacerations to head and lip. The female victim stated that a suspect entered the residence through the front door holding an assault rifle asking where the safe was. The female victim attempted to run away but was hit in the back of the head with an unknown object. The female victim informed the detective she was sexually assaulted by this suspect. A condom was recovered where the sexual acts were reported to have taken place. Afterward it was learned that another suspect stabbed the male victim approximately twenty-four times. The male victim endured five surgeries, lost vision in both eyes…but survived! A bow release was recovered from the scene. Two suspects were established during the investigation – James Tabb & Terrance Miles. Richland Parish Sheriff’s Office (RPSO) submitted DNA evidence to the Louisiana State Police Crime Laboratory (LSP) in August of 2018.
In 2015, Louisiana State Police began informing their agencies about Cybergenetics' TrueAllele probabilistic genotyping tool. In 2021, LSP began training every analyst to utilize TrueAllele routinely in the casework cycle to include and exclude references submitted for comparison. In 2022, this task was completed and TrueAllele is now a part of the LSP analyst training process. When RPSO contacted LSP in December 2021 to submit additional evidence in this case, LSP decided to review the 2018 case file to determine if utilizing TrueAllele would provide more information instead of submitting additional evidence. After reviewing the case file, LSP suggested processing the swab taken from the bow release.
The sample was processed using the TrueAllele Casework software. The software was able to objectively separate out three contributors from the complex mixture, producing a 75% major contributor and two overlapping 12% minor contributors. The major contributor matched to the victim reference with a match statistic in the hundreds of nonillions. One of the minor contributors statistically matched James Tabb with a value of 4.07 million. These match statistics provided strong support in tying both the victim and suspect references to the bow release.
When the case proceeded to trial, defense counsel requested a Daubert hearing. Defense counsel intended to question the scientific validity of TrueAllele and question the LSP analyst’s qualifications. LSP’s Technical Leader definitively answered the concerns raised during the Daubert hearing and the court ruled that the TrueAllele evidence was admissible. A jury unanimously convicted James Tabb for a minimum of 114 years.
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