But using forensic genealogy testing, detectives with the Fairfax County Police Department linked remains found 21 years ago near a drainage ditch at Lincoln Circle in McLean to Gildawie. Last month, detectives told Duperly what happened to her sister: Evidence shows the 17-year-old girl was shot in the head sometime in the mid-to-late 70s in the then-wooded McLean Street, which is now the site of an apartment complex.

Even if you’ve never taken a DNA test, a distant relative’s could reveal your identity

Police said potential leads about the female victim’s identity fell through for decades until they teamed up with forensic laboratory Othram Inc. — a company which they have used in the past. Othram scientists created a DNA profile for the victim that matched Duperly’s family tree. Investigators were then able to confirm the remains belonged to Gildawie herself in August through additional DNA testing, Fairfax County police said.

Police have made no arrests in the case, which they have ruled a homicide. They said…