San Jose, California – Nearly half a century ago, a young teacher was tragically found murdered at a California high school, just as summer vacation began. On Monday, cold case detectives revealed the identity of her killer for the first time.
Diane Peterson, who taught at Branham High School in San Jose, was stabbed to death on June 16, 1978, by a 16-year-old named Harry “Nicki” Nickerson, according to the Santa Clara County District Attorney’s Office.
She was killed shortly after the school year ended and while she was preparing her classroom for summer. A student discovered Peterson lying on the floor with a stab wound to her chest.
Investigators were able to break the cold case after engaging with Nickerson’s family this year. They learned that shortly after the murder, he confessed to stabbing the teacher. Nickerson had gone home and admitted the act to his family, who relayed this information to law enforcement.
He reportedly had a knife inscribed with the words “Dear Teacher,” which investigators noted.
“Just this year, we found out he had confessed to his family,” the DA’s office stated. “Nickerson took his own life in 1993.”
Although Nickerson was not a student at Branham High, Assistant Prosecutor Rob Baker shared that the motive behind the crime remains unclear. However, he speculated that Diane may have unknowingly interrupted some drug dealings on school grounds during the summer.
District Attorney Jeff Rosen remarked, “This wraps up a grim and tragic mystery. Peterson would have been quite elderly today had she not encountered this violent teenager. I’m pleased we’ve managed to solve this case.”
According to Baker, Nickerson was arrested four days post-murder for a different offense. “He accused police of trying to pin the murder on him, vehemently denying he killed Diane and claiming he didn’t have the knife,” Baker noted.
Police took a mugshot of Nickerson soon after the incident, noting his resemblance to a composite sketch created from eyewitness accounts of the attack.
In 1983, the family of a Branham High School student reported that he had recognized Nickerson as the assailant, alleging he had witnessed Peterson’s death. However, the student later retracted this statement. The following year, another witness claimed Nickerson admitted to killing Peterson, but authorities couldn’t corroborate that account.
After finishing high school, Nickerson became involved in a range of criminal activities, including robbery and assaults. He was fatally shot during a botched drug robbery in 1984, and no charges were filed due to the circumstances. He ultimately died from a self-inflicted gunshot wound in 1993.
From 2023 to 2024, the DA’s Crime Institute carried out extensive DNA analysis on this cold case. Unlike other recent cold case resolutions in the area, investigators didn’t find a DNA match. Instead, the breakthrough came when Nickerson’s family approached the police.
“It’s now almost 50 years since a young teacher’s life was so tragically cut short,” noted San Jose Police Chief Paul Joseph. “While the suspect won’t face trial, I hope this outcome brings some measure of closure for the victim’s family and the community that has mourned her for so long. No matter how much time passes, we will always pursue the truth.”
The DA’s Cold Case Unit, established in 2011, has successfully resolved over 30 cold case murders since 1969. The Peterson case marks the fourth such resolution by the office this year.
Peterson’s family expressed, “Diane was a beautiful and wonderful person who was truly overlooked.”
