31 Years Cold Case Solved by a Family Tree — He Had a Relative Who Took a DNA Test

In August 1990, 17-year-old Michelle Koski vanished just two blocks from her home in the Lake City neighborhood of north Seattle. Days later, her body was found in an overgrown blackberry thicket off Highway 522 near Echo Lake Road in Snohomish County. For thirty-one years, the killer lived in complete freedom because his crime scene DNA was a complex two-person mixture that traditional police databases couldn't read. He had no DNA in CODIS. But an innocent relative took an at-home ancestry test—and ignited a genetic beacon that led straight to his door. In this full-length documentary investigation, we examine the landmark 31-year cold case that transformed forensic science: • The final hours of 17-year-old Michelle Koski in Lake City • The crime scene in the woods off Echo Lake Road and the autopsy findings • The massive 1990 manhunt and cross-investigation with the Green River Task Force • Why traditional forensic DNA hit a brick wall for over three decades • The bioinformatics breakthrough: How Parabon NanoLabs mathematically deconvoluted a degraded two-person DNA mixture • Genealogist Deb Stone's year-long excavation of two centuries of family trees • The suspect unmasked: Robert Anthony Brooks, released from prison just four months prior, living less than 500 feet from Michelle's front door • How detectives retrieved a preserved postmortem blood sample to confirm a 1-in-multiple-quadrillions match • The retirement of legendary Detective Jim Scharf after 45 years of law enforcement service 🔔 If you believe every cold case victim deserves justice and their stories must never be forgotten, please SUBSCRIBE to ColdCase Crime File and turn on notifications: @ColdCaseCrimeFile