Mark Personette, now 80, was sentenced to life for the 1978 strangling of 15-year-old Marissa Harvey after genetic genealogy and trash DNA closed a decades-old cold case.
A San Francisco jury convicted Mark Stanley Personette of first-degree murder in the killing of 15-year-old Marissa Harvey, and a judge sentenced the 80-year-old to life in prison with the possibility of parole after seven years, the district attorney’s office announced on Sept. 30.
True Crime News reported that investigators identified Personette through investigative genetic genealogy in 2021, then matched his DNA to evidence left on the teenager’s clothing and a piece of gum recovered from the crime scene nearly half a century earlier.
Harvey had been visiting her sister in San Francisco when she went to Golden Gate Park on March 27, 1978, to go horseback riding. The next day, a group of surfers found her body in the underbrush. An autopsy determined she had been strangled and sexually assaulted, and blood on a leaf showed she was attacked where she was found.
For more than four decades the case sat cold. Then advanced DNA work, trash surveillance, and a search warrant did what earlier investigators could not.
Genetic genealogy put a name to a 1978 crime scene
San Francisco police reopened the cold case in October 2020. By 2021, investigative genetic genealogy had pointed to Personette as a suspect, the district attorney’s office said.
Fox News reported that authorities arrested Personette, then 76, in suburban Denver on suspicion of killing Harvey after the case was reopened with advanced investigative methods. Police Chief Bill Scott said the victim’s family had pressed for justice for more than four decades.
"For more than four decades, Marissa Harvey’s family members have been relentless advocates to bring her killer to justice, and we hope this development in the case begins to bring a measure of healing and closure they’ve been too long denied," Police Chief Bill Scott said.
That same DNA-driven approach has closed other long-dormant killings, including a 2003 Dayton strangulation cold case broken by a DNA match years after the crime.
FBI investigators then watched Personette at his Denver home and collected personal hygiene garbage containing his DNA. A search warrant at the residence showed he separated those materials from other trash. Lab testing matched his DNA to evidence on Harvey’s sweater and jeans and to gum recovered from the scene.
The New York Post reported that dried gum stuck to the victim’s back was among the evidence that finally tied Personette to the attack, and that warrants also turned up a San Francisco map and California license plates at his Colorado home.
District Attorney Brooke Jenkins and prosecutors framed the sentence as long-delayed accountability for a crime that stole a child’s life.
"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.
Assistant District Attorney Heather Trevisan said the sentence reflected the cruelty of the conduct and the harm done to Harvey.
"This sentence reflects the extraordinary cruelty of Mark Personette’s conduct and the harm he caused," said Assistant District Attorney Heather Trevisan.
Trial testimony reached beyond the 1978 killing
At trial, another woman testified that Personette had allegedly raped her in New Jersey in 1979, the year after Harvey was killed, according to the district attorney’s account of the case. The package does not show whether that allegation produced a separate conviction; it entered this case as witness testimony.
Cold-case units keep turning to the same toolkit. Arlington police used an FBI DNA genealogy program to identify a suspect in a 2012 stabbing, and similar genetic work has pulled names out of evidence lockers that sat untouched for a generation.
Personette was 80 at sentencing. Harvey was 15 when she walked into Golden Gate Park and never came home. The gap between those ages, and the nearly 50 years between the murder and the verdict, is the story the jury closed.
Life with parole possible after seven years is the term the court imposed for first-degree murder. Prosecutors called it accountability. Families who waited decades called it overdue. The record shows a teenager strangled and sexually assaulted, a suspect identified by genealogy and trash DNA, and a conviction entered when the defendant was already an old man.
Investigators elsewhere have used the same methods to break other stalled murders, from a 1988 Orlando killing solved nearly four decades later to charges in a 1990s neighbor murder once written off as unsolvable.
Harvey’s family spent more than forty years pressing police and prosecutors to keep the file alive. When the science finally caught up, the state charged Personette, tried him, and secured a first-degree murder conviction. The sentence sends him to prison for life, with a parole hearing possible after seven years.
Forensic DNA has rewritten the odds on cases once left for dead. An Ohio assist on a 30-year California cold case showed the same pattern: old evidence, new testing, a name where there had been none.
Personette’s Denver search and the match to Harvey’s clothing and gum turned a 1978 park killing into a prosecuted murder. The jury’s verdict and the life term close the official chapter. They do not restore the years Harvey lost, or the decades her family spent waiting for a name.
Justice delayed is still justice owed, and DNA finally forced this killer to answer for a child who never made it home from the park.
