FAIRFIELD — Local police are using a little-known forensic tool — touch DNA — to track a burglar who was spotted Wednesday night in a motor vehicle.

The burglar fled the scene when the car’s owner confronted him around 8:30 p.m. on Willow Street, but he left something behind — his skin cells, Fairfield Police Chief Tom Gould said Thursday.

“The subject fled on foot, and we called in a canine from the Somerset County Sheriff’s Office,” Gould said. “We didn’t locate him, but we did get DNA — touch DNA.”

The touch DNA method of investigation analyzes skin cells left behind when someone touches a victim, a weapon or something else at a crime scene, according to a report in Scientific American. Police have been using the method for about 10 years. It was used in 2005 to clear the family of JonBenet Ramsey of any wrongdoing in the 6-year-old Colorado girl’s 1996 death, according to the magazine’s online edition.

“You only require a very small sample,” Fairfield police Sgt. Paul St. Amand said. “We have a collection kit that’s basically like a sterile Q-tip, and we apply some sterile water to it, and you just lightly swab the area that’s been touched. Skin cells are left when a person touches the object.”

St. Amand said local police have been using touch DNA for several years and find they have better luck with that than with using just fingerprints. The touch samples are processed at the state police crime laboratory in Augusta and later compared to samples taken from the suspect.

Years ago, in order to perform DNA analysis on a crime scene or victim, forensic investigators needed a blood or a semen stain to compare with a sample taken from a suspect in a crime, either with a mouth swab or a hair clipping. To use touch DNA, the investigator doesn’t have to see anything. A good sample of DNA requires only seven or eight cells from the outermost layer of the subject’s skin, according to the Scientific American report.

St. Amand said the sample taken from the 2005 GMC Yukon, which had been broken into, was lifted from the window on the vehicle’s driver’s side, where the burglar had rummaged through a purse.

“I think what happened was he tried to close the door softly, and we had a fresh fingerprint on the window,” he said. “Afterward, we caught the fingerprint with the latent dust.”

DNA evidence — whether blood samples or skin cells — is reliable and holds up in court if the crime laboratory can determine that the sample is a viable one, said Maeghan Maloney, district attorney for Somerset and Kennebec counties. The only problem is getting the sample examined under a microscope, because of a backlog of cases at the crime laboratory, she said.

“DNA is something that’s microscopic, so they’re able to compare it to the DNA of the offender. Then the lab can tell us of the reliability of that information,” Maloney said. “If they don’t have a full DNA strand, the lab will say that, but given the microscopic nature of DNA, a skin cell can be enough. Skin cell DNA is not less reliable than hair DNA.”

St. Amand said the suspect is a white man, appearing to be 17 to 19 years old. He was wearing a gray hooded sweatshirt and black sweat pants. He is about 5 feet, 8 inches tall and has short brown hair.

Doug Harlow — 612-2367

dharlow@centralmaine.com

Twitter: @Doug_Harlow