Teen ID'd as Killer in San Jose Teacher's Murder

Nearly five decades ago, Diane Peterson was found lying in a hallway at Branham High School in San Jose, her life ended by a single stab wound to the chest. She was 26 years old, a teacher just starting her career, cleaning out her classroom as summer break began.

Her murder would remain unsolved for 47 years.

That changed in 2025, when a long-held family secret finally came to light.

The Day After School Let Out

It was June 16, 1978. The final bell of the school year had already rung the day before, and students were gone for the summer. Peterson stayed behind with other teachers to pack up her classroom. But she never made it home. A student discovered her lifeless body near her classroom.

From the beginning, investigators had leads. A 16-year-old student named Harry “Nicky” Nickerson quickly drew attention. Witnesses said he resembled a composite sketch of the killer. One person even reported seeing him with a knife inscribed with the chilling words “Teacher Dear.”

Yet, despite multiple tips and even a witness who said Nickerson confessed, no charges were ever filed.

Years of Leads - Then Dead Ends

The case file grew thick with statements, sketches, and doubts. In 1983, the family of a student told police their son had witnessed the killing and identified Nickerson as the attacker - but that witness later recanted.

A year later, another person claimed Nickerson admitted to killing Peterson after she allegedly caught him dealing drugs. Still, it wasn’t enough.

Nickerson’s life spiraled after high school. He was arrested for armed robbery, assault with a deadly weapon, and kidnapping. In 1984, he was shot during a failed drug robbery attempt and survived. He died by suicide in 1993.

A Family Confession Changes Everything

In 2025, everything changed. A relative of Nickerson’s contacted police and said Nickerson had come home minutes after the stabbing and confessed. The relative had kept the secret for almost 50 years, possibly out of fear, but could no longer carry the burden. They told authorities Nickerson admitted to stabbing Peterson that day in 1978. The DA’s office confirmed the relative had no involvement in the murder and wouldn’t face charges.

Though Nickerson is no longer alive to face justice, authorities officially closed the case. Death made prosecution impossible.

Seeking Justice After Death

“This marks the end of a terrible and tragic mystery,” said Santa Clara County District Attorney Jeff Rosen, according to a Santa Clara news release. “Ms. Peterson would have been a senior citizen today if she had not crossed paths with this violent teenager. I wish she was.”

San Jose Police Chief Paul Joseph called it “a solemn reminder” that justice can still be pursued no matter how much time has passed, according to PEOPLE.

Peterson’s family, who had waited for answers through decades of heartbreak, expressed gratitude to investigators for never giving up. “Diane was a beautiful and wonderful person who is missed dearly,” a relative said, according to PEOPLE.

A Case Closed - and a Community Reminded

For nearly 50 years, the murder of Diane Peterson haunted her school, her city, and her family. Now, it stands as one of the oldest homicide cases to be solved in Santa Clara County.

There won’t be a trial. No cross-examinations or verdict. But for those who loved Diane, the truth still matters.

References: A Teacher Was Killed Nearly 50 Years Ago - Now the Suspect Has Been ID’d, and the Knife Held a Creepy Message | Teen Identified as Killer in Decades-Old Murder of Teacher | DA Cold Case Unit, SJPD Solve 1978 Murder of High School Teacher; Killer Carried Knife Inscribed with “Teacher Dear”