Update provided on investigation of 1970s cold cases linked to serial killer Warren Forrest

The Clark County Sheriff’s Office Cold Case Team located and interviewed subject because he was believed to have information relevant to Jamie Grissim’s disappearance

The Clark County Sheriff’s Office Major Crimes Unit is cancelling the “Attempt to Locate” bulletin issued earlier this year regarding 72-year-old Matt (Mathew) W. McClure. The bulletin was disseminated initially as part of the ongoing investigation into the 1971 disappearance of Jamie Grissim, believed to be an early victim of convicted serial killer Warren Leslie Forrest. 

The Clark County Sheriff’s Office Cold Case Team sought the public’s assistance in locating McClure because he was believed to have information relevant to Grissim’s disappearance, based on a possible sighting in the winter of 1971. McClure was never considered a suspect in this case. Due to his believed association with the local unhoused community, locating and contacting him required assistance from the public. 

Thanks to tips received from the community, investigators successfully located and interviewed McClure. 

While the details of the interview remain part of an active investigation and are not being released at this time, investigators report that the information provided by McClure appears credible and is consistent with previously known details surrounding Grissim’s disappearance, particularly those supporting the belief that her remains may be in the Dole Valley area. Grissim was reported missing in December 1971. In the Spring of 1972, her high school identification was found on the side of the road in Dole Valley, approximately 1.5 miles north of where two murder victims’ remains were discovered in 1974. Those two victims were later identified as Carol Valenzuela and Martha Morrison. Warren Leslie Forrest was convicted of Morrison’s murder in February 2023. 

McClure is not suspected of any involvement in Grissim’s disappearance or any related crime. 

As a result of the new information and McClure’s cooperation, the Cold Case Team is coordinating with Washington State Search and Rescue and Clark County Search and Rescue to plan an additional search effort in the Dole Valley area. This search will utilize human remains detection dogs — specialized canines trained to locate human remains that may be deeply buried and several decades old. The search operation is pending final logistical planning and resource availability. 

Recently, the Seattle Division of the Federal Bureau of Investigation has joined the investigation and is consulting on laboratory and investigative matters. 

Further updates will be provided as the investigation progresses. Anyone with information on this case is asked to call the Cold Case Tip Line at (564) 397-2036. 

Information provided by the Clark County Sheriff’s Office.