Justice After 30 Years: Conviction Won in Cold Case Murder

In February 1975, the community of Richmond Beach in Shoreline was shocked by the murder of 16 year-old Diana Peterson. Diana was found stabbed to death in the backyard of her parents' home after she had gone to a nearby pizza parlor with some friends.  Police immediately began investigating two possible suspects, Diana's high school boyfriend and a neighbor boy, James Groth, who was known to be infatuated with her.  Police interviewed Groth several times just after the murder, but could not establish enough evidence to arrest him.  The case soon grew cold, and remained unsolved for over 32 years.

In 2004, the PAO, along with the Seattle Police Department and the King County Sheriff's Office, formed a Cold Case Taskforce.  Investigators and prosecutors began a comprehensive, systematic review of King County's "cold case" homicides, including the murder of Diana Peterson.  King County Sheriff's Detectives and prosecutors pieced together the decades-old evidence and re-interviewed old witnesses who had information about Groth.  Groth was also re-interviewed and made some incriminating statements.

In 2007, Senior DPA Carla Carlstrom used the newly gathered evidence to file a murder charge against Groth.  Earlier this month, Groth was convicted by a jury of Murder in the Second Degree.  Because the crime took place in the 1970s, Groth will be sentenced under our State's former "indeterminate" sentencing system, which calls for a minimum term of 10 years in prison to life.  Groth will be subject to review by the State Parole Board after he serves his minimum term.

Speaking on behalf of the Peterson family, Diana's brother John Peterson commented that a conviction will help the family put this tragic crime behind them and finally get "some closure."

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