How CMPD used new DNA technology to crack 35-year-old cold case

CHARLOTTE — New DNA technology helped the Charlotte-Mecklenburg Police Department solve the 1990 killing of Kim Thomas, leading to an arrest 35 years after she was stabbed to death inside her Cotswold home. Investigators said on Thursday advanced software allowed crime lab analysts to reexamine old evidence and strengthen the case against a longtime suspect.

Channel 9’s crime reporter Hunter Sáenz spoke with CMPD’s Crime Lab director to explain how they did it.

Matthew Mathis, who has been the director since 2008, said his team ran back the evidence from 35 years ago at the crime lab on the fourth floor.

Sáenz wasn’t allowed in their lab, but CMPD provided video of it.

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Over the years, lab technicians tested a pubic hair found on Kim Thomas, along with DNA on a rug in her house and on her bed.

That hair was consistent DNA belonging to Marion Gales, a handyman in the neighborhood.

“Consistent” is a critical word in the case.

“When DNA is degraded or there’s small amounts of DNA, we may not have a complete profile, therefore, it may be consistent with, as opposed to identify specifically to that individual,” Mathis said.

Mathis explained the new technology used to crack the case.

“Probabilistic genotyping software,” Mathis said. “That software uses mathematical algorithms and modeling to help the DNA analyst sort through all of that information and make sense of all the DNA profiles that are present.”

The software helps in cases of complex, low-quality, or mixed DNA samples.

It allows analysts to be more confident in the DNA profile that was present. In this case, that of Marion Gales.

The new technology gives the lab more tools, which assist prosecutors in their cases.

“It has the opportunity to advance cases, not only in the initial investigation, but also throughout the court system,” Mathis said. “It helps build a fuller picture, if you will, for them to help advance their investigation.”

CMPD has been using the new high-tech software since April2024.

Mathis said it can be really helpful in cold cases, and it’s something they are using more often.

Gales admitted to being in Kim Thomas’ home the day she was killed after her husband left for work, prosecutors said. He also confessed to having sexual contact with her. For years, he said he had nothing to do with the killing.

VIDEO: Suspect arrested 35 years after killing of Kim Thomas