Detectives in San Jose say they have solved a grisly 1978 cold-case murder of a high school teacher who was found stabbed to death in the school’s hallway with a knife marked “Teacher Dear.”
The violence unfolded on June 16, 1978, at Branham High School one day after school let out for summer and teachers were breaking down their classrooms for the break.
Detectives said a student discovered Diane Peterson on the floor near her classroom suffering from a single stab wound to the chest.
Harry “Nicky” Nickerson, a 16-year-old at the time, was a suspect in the brutal murder. A 1978 photo of Nickerson taken four days after the killing appeared similar to a composite sketch of the suspect based on eyewitness accounts.
One of those witnesses told police that Nickerson confessed to the killing and that he had seen him carrying a knife that had the words “Teacher Dear” written on it.
“Police at that time were unable to corroborate the claim,” officials at the Santa Clara County District Attorney’s Office said in a news release.
Then, in 1983, family members of a Branham student told investigators that their son claimed to have seen the killing and identified the NIckerson as the one who did it, but the student later denied making that claim.
A year later, in 1984, yet another witness told detectives that Nickerson implicated himself in the teacher’s murder and that he’d done it because Peterson caught him in the middle of a drug deal.
Nearly 40 years later, the district attorney’s crime lab conducted extensive DNA testing on the case but were never able to identify the perpetrator, until a family member came forward in 2025.
“The relative admitted to police that Nickerson came to their home minutes after the killing and confessed to having stabbed Peterson,” officials said.
Nickerson’s life following the murder was a series of run-ins with law enforcement.
He was arrest and convicted on charges of armed robbery, assault with a deadly weapon and kidnapping, the release stated. In 1984, he was critically shot during an attempted drug robbery, though he survived the ordeal.
Then, in 1993, he took his own life with a self-inflicted gunshot wound, officials said.
“This marks the end of a terrible and tragic mystery. Ms. Peterson would have been a senior citizen today if she had not crossed paths with this violent teenager. I wish she was,” Santa Clara County DA Jeff Rosen said. “I am pleased that we have solved this case, even though the murderer is not alive to face justice. I wish he was.”
