Nearly 50 years after a young teacher was found stabbed to death in a San Jose high school hallway, the Santa Clara County District Attorney’s Office and the San Jose Police Department have officially identified her killer.
Image of Harry Nickerson (date unknown). Photo, Santa Clara County District Attorney’s Office
Harry “Nicky” Nickerson, 16-years-old at the time, stabbed Diane Peterson in 1978 at Branham High School. Just this year, investigators learned that he had confessed the killing to a family member.
Earlier, a witness had told police that Nickerson had confessed the crime and that he had seen him carrying a knife that had written on it: “Teacher Dear.” Police at that time were unable to corroborate the claim.
Nickerson committed suicide in 1993.
“This marks the end of a terrible and tragic mystery,” said District Attorney Jeff Rosen. “Diane Peterson would have been a senior citizen today if she had not crossed paths with this violent teenager. I wish she was. I am pleased that we have solved this case, even though the murderer is not alive to face justice. I wish he was.”
"Nearly five decades have passed since a young teacher’s life was tragically taken," said San Jose Police Chief Paul Joseph. "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 truth — because every victim matters, and every life deserves justice."
On June 16, 1978, a student found Peterson lying on the floor near her classroom with a single stab wound to her chest. The killing occurred the day after school recessed for summer while teachers were cleaning their classrooms for the break.
Nickerson was a suspect in the killing. A 1978 booking photo of Nickerson four days after the killing bore a strong similarity to a composite sketch based on eyewitness accounts of the attack. In 1983, the family of a Branham student alerted police that their son claimed to have seen the killing and identified Nickerson as the one responsible.
The student, however, later denied making that statement. In 1984, a witness told police that Nickerson implicated himself in the killing, which he said was in response to discovering Nickerson in the act of a drug deal. Between 2023 and 2024, the DA’s Crime Lab conducted extensive DNA work on the case to identify the perpetrator but was unsuccessful.
In 2025, investigators broke the case after meeting with a family member of Nickerson. The relative admitted to police that Nickerson came to their home minutes after the killing and confessed to having stabbed Peterson.
In the years following the murder, Nickerson was arrested and convicted of such charges as armed robbery, assault with a deadly weapon, and kidnapping. He was shot and critically injured in 1984 while attempting to commit a drug robbery. Given the circumstances, no charges were filed.
He died in 1993 from a self-inflicted gunshot wound.
The DA’s Cold Case Unit was established in 2011. Since then, the DA’s Office has solved over 30 cold case murders from as early as 1969. The Peterson case is the fourth cold case homicide solved by the DA’s Office in 2025.
A family member of the victim, who wishes to be unidentified, thanked investigators for “not giving up for 47 years.”
The relative said: “Diane was a beautiful and wonderful person who is missed dearly.”
