Patricia Agnes Gildawie: Teen's skeletal remains identified through relative's DNA after she went missing in 1975

The skeletal remains of a teenage girl who went missing in the US state of Virginia nearly 50 years ago have been identified thanks to a DNA breakthrough.

Patricia Agnes Gildawie, also known as Choubi, was last seen in the city of Fairfax on 8 February 1975. She was 17 at the time.

On 21 September 2001, a woman's remains were found by a construction crew behind an apartment complex and near a drainage ditch, along with some clothing, in McLean.

Fairfax County police say the remains have now been identified as those of Ms Gildawie.

Following the discovery 21 years ago, an initial review found she died from a gunshot wound to the head. The report also indicated the remains were likely that of an African-American female in her late teens to early 20s.

However, cold case detectives have been working this year with Othram, which does DNA testing and forensic-grade genome sequencing, and established the remains belonged to a white female.

The testing identified a half-sister, Veronique Duperly, who shared Ms Gildawie's story.

'100% match within 15 minutes'

Ms Duperly has described the moment last month when detectives told her the company's testing had linked her results to Ms Gildawie.

"When I gave them my DNA, they sent it to the lab while they were sitting here in my living room, and they had a 100% DNA match within 15 minutes," she said.

Ms Duperly said Ms Gildawie was dating an older man at the time, who loaned her a white Cadillac Eldorado with red interior that she was driving the last time Ms Duperly saw her.

It was also the day Ms Duperly noticed bruises on her half-sister.

"Bruises on her upper arms, her shoulders, and the back of her legs," she told NBC News.

"I said, 'Well, why are you so black and blue?' She said, 'I fall a lot.' I said, 'No, you don't.'"

'We know the killer is still out there'

Police are keen to talk to her boyfriend, but they don't know his name - only that he was in his 30s at the time of Ms Gildawie's death and worked at a now-closed upholstery store near Church Street and Lawyer's Road in the town of Vienna, Virginia.

Ms Gildawie was born in France in February 1958 and came to the US when she was eight months old. In the early 1970s, she moved to Fairfax.

"We're moving fast and furious on this case. We know the killer is still out there," said Ed O'Carroll, bureau commander of major crimes and cyber and forensics.

He added: "Identifying this young woman solves a mystery that has been more than 47 years in the making.

"Our community should take comfort in knowing that our detectives never stop working these cases.

"Advancements in technology have given my cold case detectives an opportunity to pursue fresh leads and bring some relief to families that have been long-suffering with the unknown."

No information has been released on any charges over Ms Gildawie's death. Police continue to investigate, using fresh information from the family.