(CNN) -- A victim of Washington state's notorious "Green River Killer" has been identified 29 years after her disappearance, when a relative saw a TV movie about the serial murderer in April and family members gave DNA samples to investigators, authorities said Tuesday. The victim was Sandra Denise Major of Rochester, New York, who was a 20-year-old prostitute when she got into a truck on December 22, 1982, and was never seen again, said Sgt. Cindi West of the King County, Washington, sheriff's office. Gary Leon Ridgway, dubbed the Green River serial killer, pleaded guilty in 2003 to killing 48 women, including Major, though her remains hadn't been identified at the time, West said. The 48 guilty pleas gave Ridgway more murder convictions -- though not necessarily more slayings -- than any other serial killer in U.S. history.
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A cousin watches Lifetime's "The Capture of the Green River Killer" in April
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The family recalls how Sandra Denise Major went missing in Seattle in 1982
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Major's remains are identified after family members give DNA samples
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Gary Leon Ridgway admitted killing 49 persons, mainly runaways and prostitutes
"Since (Major) was last known to be in @placeholder and ... she was working as a prostitute, (her family) contacted detectives," West said.