Police use DNA to solve murder mysteries and rapes.

They used it last year to determine who spit into a customer’s soda at a Chili’s restaurant in Clay, New York.

The state police crime lab compared DNA from some spit that Ken Yerdon found inside his soda with a swab of saliva from the man who had waited on Yerdon at Chili’s – Gregory Lamica.

The DNA was a match, according to court papers. Lamica was charged with disorderly conduct and pleaded guilty.

Yerdon and his wife, Julie Aluzzo-Yerdon, had dinner at Chili’s on Route 31 on July 28, as they did about once a week. Lamica, then 24, was their waiter.

They had a couple minor complaints – undercooked broccoli and chips not being served, they said. They told Lamica and he seemed annoyed with them, Ken Yerdon said.

“They were busy — we understood,” Julie Aluzzo-Yerdon said. “We were patient with him, but we could tell he was annoyed with us. All Ken said to him was, ‘Are you OK? Have we done something to offend you?’ And he said, ‘Oh, no, no.”

When they were getting ready to go, the Yerdons told Lamica they wanted to get their drinks refilled and to take them in to-go cups. Lamica brought them the cups, as if he’d expected them to pour the remains of their drinks into the cups, according to a police report.

Ken Yerdon told Lamica they wanted him to refill the cups, since the drinks on their table were almost gone, he said. Lamica seemed annoyed again, and took the cups to the back of the restaurant, Yerdon said.

On their way out, they Yerdons saw Lamica and noticed that he wouldn’t make eye contact, the police report said.

Ken Yerdon took two sips from the cup. He wasn’t able to see inside because it had a lid and was Styrofoam. As they were driving home, the lid popped off.

“I saw the spit in the cup,” Ken Yerdon told Syracuse.com. “It wasn’t regular spit either. It was definitely a loogie.”

Yerdon took a picture of it, dropped his wife and 12-year-old son off at their home in Clay and drove back to Chili’s.