Green River Killer Gary Ridgway's youngest victim identified

Gary Ridgway, inset, terrorised the Seattle area in the 1980s. Four of the victims - including Wendy Stephens, pictured - had not been identified. Photo / Supplied

Genetic genealogy helped identify the youngest known victim of one of the nation's most prolific serial killers almost 37 years after her remains were discovered near a baseball field south of Seattle.

Wendy Stephens was 14 and had run away from her home in Denver before Gary Ridgway, the Green River Killer, strangled her in 1983, the King County Sheriff's Office announced on Monday.

Ridgway terrorised the Seattle area in the 1980s and has pleaded guilty to killing 49 women and girls since 2003. Four of the victims - including Stephens - had not been identified.

Green River Killer Gary Ridgway listens during his arraignment on charges of murder in the 1982 death of Rebecca Marrero in 2011. Photo / AP

"Ridgway's murderous spree left a trail of profound grief for so many families of murdered and missing women," King County Prosecutor Dan Satterberg said in a written statement.

"We are thankful that Wendy Stephens' family will now have answers to their enormous loss suffered nearly 40 years ago."

Researchers at the DNA Doe Project, a volunteer organisation that uses publicly available DNA databases to find relatives of unidentified victims, helped make the identification.

Stephens' remains were found in a wooded area next to a baseball field in what is now the suburb of SeaTac on March 21, 1984, after the groundskeeper's dog came home with a leg bone.

She had been killed a year or more earlier, investigators said, and she is believed to have been Ridgway's youngest victim.

The remains of another Ridgway victim, Cheryl Wims, were discovered at the same time.

Stephens' family requested privacy and declined to speak with reporters, said Sgt. Tim Meyer, a spokesman for the sheriff's office.

Wendy Stephens. Photo / Supplied

Green River Killer's victims. Photo / AP

Ridgway preyed on young women in vulnerable positions, including sex workers and runaways, mostly from 1982 to 1984. Though he had long been a suspect, his role was unconfirmed for nearly two decades before advances in DNA technology allowed detectives to identify him as the Green River Killer in 2001 from a saliva sample they had taken in 1987.

Ridgway claimed to have killed dozens more women than he was charged with - so many he said he lost count.

Rosemary Fries, left, mother of Green River Killer victim Shirley Sherrill speaks at the sentancing of Ridgway as her daughters Deanna Brewer, centre, and Michele Andrews listen. Photo / Getty Images

He pleaded guilty in a deal to avoid the death penalty after agreeing to help investigators find additional remains.

He is now 71, spending the rest of his life at the Washington State Penitentiary.