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TrueAllele finds match for DNA mixture in 12-year-old murder of college student

Excerpts from the original Forensic® article by Michelle Taylor.

Wisconsin police arrested a man who allegedly stabbed and strangled a 21-year-old college student to death in the middle of the day in her house in 2008. The accused, David Kahl, has been a suspect from the very beginning but lab tests have been inconclusive, until now. Cybergenetics and TrueAllele have finally matched DNA from the victim Brittany Zimmermann’s jeans to Kahl.

During the murder, DNA from the assailant was left on Zimmermann’s shirt and jeans. The Wisconsin Crime Laboratory analyzed the DNA samples, which were all mixtures, in 2010 for the first time. At the time, the DNA mixture found on Zimmermann’s shirt was not eligible for CODIS upload, and could not be identified any further.

The DNA left on the victim’s jeans was determined to be a mixture of three or more persons, including one male. However, even amplified by PCR, the small sample size and mixture did not allow forensic lab analysts to determine a source. When this DNA sample was re-analyzed in 2014 and 2016, the results were, again, inconclusive.

The Madison Police Department did not give up, though. As technology advanced, the police surveyed their options. They ended up submitting DNA samples from the victim’s shirt and jeans to Cybergenetics for analysis.

On November 30, 2018, three days after receiving the evidence, Cybergenetics returned a report identifying Kahl as the source of the DNA found on each sleeve of the victim’s shirt. The DNA mixture on Zimmermann’s jeans was forwarded to Cybergenetics in December 2019. A February 2020 report from the company indicated a DNA match to Kahl on three separate areas of the jeans.

For the full story, please see the original Forensic® article.

Photo: Brittany Zimmermann. Credit: MPD.

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