Diane Peterson Murder Case Solved 47 Years Later

Nearly 50 years after a beloved teacher was stabbed to death in a California high school hallway, authorities say they’ve identified her killer — and it was one of her students.

Harry “Nicky” Nickerson, who was 16-years-old at the time, stabbed Diane Peterson in 1978 at Branham High School in San Jose, the Santa Clara County District Attorney’s Office said in a statement. 

Investigators learned this year that Nickerson allegedly confessed the killing to a family member. Another witness told police that Nickerson admitted to the stabbing and had once been seen carrying a knife with “Teacher Dear” written on it.

Police at the time were unable to corroborate this claim, the statement from the prosecutor’s office said. Nickerson died by suicide in 1993. 

On June 16, 1978, a student found Peterson lying on the floor near her classroom with a single stab wound to her chest. Prosecutors say that the stabbing occurred the day after school let out for summer break while teachers were cleaning out their classrooms. 

Nickerson was an initial suspect in the killing. A 1978 booking photo authorities took of him resembled a composite sketch of the suspect created based on eyewitness accounts of the attack, the statement said. 

Prosecutors say that in 1983, the family of a student at the high school claimed that their son saw the killing and identified Nickerson as the person responsible, but the witness later denied making the statement. 

In 1984, a witness told police that Nickerson implicated himself in the killing, allegedly saying it happened after Peterson caught him dealing drugs, according to the prosecutor’s office.

Between 2023 and 2024, the district attorney’s office said its crime lab conducted extensive DNA testing but was unable to identify a suspect.

Prosecutors say that in 2025, a relative of Nickerson’s came forward and admitted to police that Nickerson came home a few minutes after the killing and admitted to stabbing Peterson.

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“Nearly five decades have passed since a young teacher’s life was tragically taken,” San Jose Police Chief Paul Joseph said in a statement. “While the suspect will never stand trial or face the consequences for his actions, we hope this resolution brings a measure of peace to the victim’s loved ones and to a community that has carried this loss for far too long. Let this serve as a solemn reminder: no matter how much time passes, we will continue to seek the trust – because every victim matters, and every life deserves justice.” 

A family member of Peterson’s thanked investigators for “not giving up for 47 years,” according to the statement from the district attorney’s office. “Diane was a beautiful and wonderful person who is missed dearly,” the unidentified family member said.