SAN FRANCISCO, CA — Marissa Harvey, 15, went to Golden Gate Park to ride horses while visiting her sister in San Francisco during the spring of 1978. But she never made it back home.
While out that day, she visited nearby Sutro Heights Park, where Mark Personette violently attacked her, sexually assaulted her and used some form of cord to strangle her to death, according to authorities.
Personette then placed her body in the underbrush of the park, where it was found the following day by surfers walking through the area, according to the San Francisco District Attorney's Office.
On Wednesday, Personette, 80, was sentenced to life in prison with parole eligibility after seven years, prosecutors said.
"After almost 50 years, Mr. Personette is finally being held accountable for his heinous crimes against Marissa and will spend the rest of his life in prison," District Attorney Brooke Jenkins said in a statement. "While nothing can bring Marissa back to her family, today's sentence hopefully leaves her family with a sense that justice was done for all that they have endured."
Marissa's case puzzled law enforcement for decades. Personette had left behind DNA on Marissa's jeans and sweaters, along with a piece of dried gum on her back, prosecutors said.
But forensic limitations stalled the case. Until DNA testing in the early 2000s revealed the first clue in decades: a male DNA profile.
Investigators identified Personette as a suspect in 2021 after a "through investigative genetic genealogy," prosecutors said.
FBI agents surveilled Personette at his Denver, Colorado home, where he at some point traveled more than 15 miles away to a Walmart parking lot to throw away trash, prosecutors said. Agents retrieved the trash, which included personal hygiene items with his DNA, authorities said.
Authorities secured a search warrant for Personette's home and found he had been separating all personal hygiene items from his other trash. Although he denied ever having visited San Francisco, agents found 1970s maps of the city and a set of California license plates with a 1979 registration sticker at his home, prosecutors said.
After further testing, Personette's DNA matched the one that had been found on Marissa's sweater and jeans, and the gum, prosecutors said.
During the trial, a woman testified that Personette had raped her as a teen in a wooded area of New Jersey back in 1979, prosecutors said.
Jurors found Personette guilty of first-degree murder following a trial in November.
"This sentence reflects the extraordinary cruelty of Mark Personette's conduct and the harm he caused," said Assistant District Attorney Heather Trevisan. "He will spend the rest of his life facing the consequence of taking hers."
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