Police in Washington have finally managed to identify the killer of an 18-year-old woman who was found dead on a riverbed 36 years ago.
It was August 28, 1988, when fishermen on the Puyallup River discovered the body of Tracy Whitney, a teenager who had last been seen the day before leaving a Burger King after an argument with her friends.
Her body was nude, and an autopsy revealed that she had died as a result of asphyxia from strangulation and probable smothering.
According to the Pierce County Sheriff's Department, Tracy was also believed to have been sexually assaulted.
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After Tracy was found, detectives launched an investigation and conducted interviews to try and track down the person responsible for her murder.
They collected DNA samples, but at the time they were unable to identify the killer, and the case went cold.
In 2005, police used the DNA they had collected through a national database, but still no positive matches were found.
It wasn't until 2022, following a grant from the Washington State Attorney General's Office, that a detective working on cold cases at Pierce County Sheriff's Office was able to submit the DNA to a genetic genealogy laboratory for repeat testing.
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The testing allows analysts to build a family tree based on a DNA profile, and in the case of Tracy's murder police were able to identify a member of her killer's family - namely his biological son.
The man's father, John Guillot, Jr., was confirmed to be a match for the DNA collected by investigators at the time of Tracy's murder. However, his death in January 2022 means he could not be brought to justice.
On Saturday (November 30), Pierce County Sheriff's Office announced the case had been solved.
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They wrote on Facebook: "There were no connections between Tracy and Guillot Jr and detectives believe this was a stranger abduction, rape and murder.
"Our Cold Case Unit is always looking into the past trying to find answers for families just like Tracy's. We are glad they can finally have an answer and some closure with the solving of this case."
Tracy's relatives have told CBS News affiliate KIRO that the resolution of the case has brought them a sense of peace.
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Her sister, Robin, added: "We believe that John Guillot Jr. likely committed other crimes. However, since he is deceased and due to current legal restrictions, his DNA cannot be uploaded into CODIS (law enforcement DNA database). We hope that this policy can be reevaluated, as it could aid in solving additional cases."
Topics: Crime, US News, Washington, True crime
Emily Brown