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.
The criminal complaint shows the police spoke to Kahl six times in the 12 years since Zimmermann was murdered. When picked up on the day of the murder, Kahl admitted he was going door-to-door in Zimmermann’s neighborhood panhandling money for crack cocaine. However, he also agreed to a DNA sample that day, which proved fruitful in the end.
Kahl and his mother have continually maintained his innocence, although Kahl has changed his story over the years. In 2009, police received a letter reportedly from an inmate at the Fox Lake Correctional Institution claiming another inmate there admitted to murdering Zimmermann. In August 2019, when the Wisconsin Crime Lab ran DNA left on the adhesive sealed area of the envelope, it matched 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.
“It has been almost 12 years since Brittany’s death. During that time, MPD never gave up on her case, tirelessly pursuing justice for Brittany and her family. Investigators have conducted hundreds of interviews, processed countless pieces of evidence, and produced thousands of pages of reports. The Dane County District Attorney’s Office and Wisconsin State Crime Lab have also been instrumental in the investigation. The dedication and persistence of those tasked with investigating this case—past and present—has never wavered,” the Madison Police Department said in a statement.
Kahl is currently incarcerated at Oshkosh Correctional Institution in Wisconsin for his seventh drunk driving arrest in 2016. He is also a registered sex offender and was convicted of second-degree sexual assault in 1993.
Photo: Brittany Zimmermann. Credit: MPD.