Robert Brooks

On July 30, 2022, police announced that they have identified Robert A. Brooks as the lead suspect in the August, 1990 rape and murder of 17-year-old Michelle Koski in Snohomish County, Washington. The case has been cleared by exception due to the death of Brooks.

Koski’s body was found on August 25, 1990 near a highway in rural Snohomish County. She had been sexually assaulted and strangled. Her head was bashed in with a piece of concrete.

The FGG investigation was performed by Parabon Nanolabs, with the assistance of genealogist Deb Stone, using a DNA mixture of the victim and perpetrator. It took about 12 months to narrow the list of potential suspects down to a cohort of two brothers.

At the time of the murder, Brooks was 22 and was staying with family a few blocks from Koski’s home and where she was last seen on August 20, 1990. At that time, someone drove her to a hangout for teenagers in Snohomish County. Brooks had been released from prison on August 18 – just two days before Michelle disappeared. His prior convictions have not been reported.

Police state that several suspects were asked to provide their DNA over the years, including Koski’s boyfriend, a local serial rapist, and the friend who drove her to the hangout. All were ruled out as being suspects.

Brooks died from natural causes in 2016 in King County.


Cavallier, Andrea. “Family, Friends Hoping for Answers Three Decades After Michelle Koski was Brutally Murdered in Snohomish, Washington.” NBC News, September 4, 2020. Accessed July 3, 2022.

Fox 13 News Staff. “Suspect Identified in 1990 Snohomish County Cold Case Murder.” Fox 13 News Seattle, June 30, 2022. Accessed July 3, 2022.

Shapiro, Emily. “Genetic Genealogy Identifies Suspect in 1990 Murder of 17-Year-Old Girl.” ABC News, July 1, 2022. Accessed July 3, 2022.

Scott, Hanna. “Snohomish County Cold Case Unit, Genetic Genealogy ID Suspect in 1990 Teen Murder.” My Northwest, July 1, 2022. Accessed July 3, 2022.


First Name Robert
Last Name Brooks
Other Names
Victims 1 (Details)
IGG Started nd
Case Cleared 2022-06-30
IGG Org Parabon


Case ID Name Age Case Opened Location Investigating Org Most Serious Charge Disposition Court
1717 Michelle Koski 17 1990-08-25 Snohomish CO, WA Snohomish CSO Second degree murder Case was cleared by exception due to death of perpetrator n/a

Last updated: February 9, 2024

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Case data and narrative licensed under CC BY 4.0: Dowdeswell, Tracey (2023), “Forensic Genetic Genealogy Project v. 2022”, Mendeley Data, V1, doi: 10.17632/jcycgvhm96.1. All other content, including photos, have been added.