Nearly half a century after a teacher was found stabbed to death in the hallway of a California high school, a teenager who had a knife inscribed with “Teacher Dear” has been named as the killer.
Diane Peterson, a 25-year-old teacher at Branham High School in San Jose, was stabbed in the chest by Harry "Nicky" Nickerson, the Santa Clara County District Attorney’s Office and the San Jose Police Department said on Monday.
The fatal stabbing happened on June 16, 1978, just as school had ended for summer break and teachers were clearing out their classrooms.
The journey to identifying Peterson’s killer was riddled with false starts, but within days of her murder, Nickerson had emerged as a suspect.
A 1978 booking photo of Nickerson bore a striking resemblance to a composite sketch created from eyewitness descriptions.
Nickerson was not a student at Branham, Deputy District Attorney Rob Baker said at a press conference Monday.
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.
Another witness reported in 1984 that Nickerson had implicated himself in the killing, which he said was in response to discovering Nickerson in the act of a drug deal. There were also reports that he carried a knife engraved with the chilling words “Teacher Dear.”
Still, none of it was enough to bring charges.
Investigators from the District Attorney’s Cold Case Unit, established in 2011, reopened the file multiple times. Between 2023 and 2024, they revisited forensic evidence and conducted extensive DNA testing.
Meanwhile, in the years following the murder, Nickerson had been arrested and convicted of multiple charges, including armed robbery, assault with a deadly weapon, and kidnapping. He was shot and critically injured in 1984 while attempting to commit a drug robbery. No charges were filed.
The break in the case came in 2025 when investigators met with a family member of Nickerson, who admitted to police that Nickerson came to their home minutes after the killing and confessed to having stabbed Peterson.
“This marks the end of a terrible and tragic mystery,” said Santa Clara County District Attorney Jeff Rosen.
“Ms. Peterson would have been a senior citizen today if she had not crossed paths with this violent teenager. I wish she was. I’m pleased we solved the case, even though the murderer is not alive to face justice. I wish he was.”
Nickerson died by suicide in 1993.
San Jose Police Chief Paul Joseph said the long-awaited resolution is bittersweet.
“While the suspect will never stand trial or face the consequences for his actions,” Joseph said, “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.”
The case is the fourth cold case homicide solved by the DA’s Office this year, bringing the total number of cold case resolutions since 2011 to over 30.
A relative of Diane Peterson, who wished to remain anonymous, expressed gratitude to investigators for their unwavering commitment: “Thank you for not giving up for 47 years.”
“Diane was a beautiful and wonderful person,” they added. “She is missed dearly.”
