It sat in a freezer, untouched, for nearly four decades.

Claus Peter Speth always thought it would be a key to solving the "Golden State Killer" case. He just didn't know when.

Speth, a pathologist who lives in the tiny borough Wenonah in Gloucester County, was the Ventura County deputy coroner assigned to the murder of Charlene and Lyman Smith in 1980. It was among the most brutal of at least a dozen murders and scores of rapes believed to have been committed by the "Golden State Killer" over a 10-year period in California.

Speth completed two rape kits of Charlene Smith. One was used by the local crime lab shortly after the murders took place. The other sat in pristine condition at the bottom of a freezer in Ventura County for nearly 38 years.

And, earlier this week, it was a crucial piece of DNA evidence that law enforcement officials say led to the arrest of Joseph James DeAngelo, a 72-year-old retired police officer. DeAngelo was charged in the Smiths' murder Wednesday, as well as several others connected to the Golden State Killer case.

"I have rarely seen such a brutal murder as Lyman and Charlene Smith," Speth, now 82, said Wednesday. "I have been on top of this ever since, hoping, hoping, hoping they would find this monster. I am so glad that they finally found this man."

The "Golden State Killer," alternatively known as the "East Area Rapist" and the "Original Night Stalker," terrorized California from 1976 to 1986. He is thought to be responsible for upwards of 50 rapes and 12 murders during that time.

The break in the case came just over the last week, said Sacramento County District Attorney Anne Marie Schubert. Law enforcement was able to tie DeAngelo to the murders using DNA, and acquired discarded DNA from his home during a stakeout to make the confirmation.

"The answer was, and always was going to be, DNA," Schubert said at a news conference Wednesday.

Speth said he remembers the scene vividly, largely due to the heinous nature of the murder.

"It was a beautiful ranch-style house. The bedroom was very large, with big, brass sliding doors. When I arrived, (the Smiths) were both lying partially covered in bed, wrists and ankles tied," he said.

Speth's examination proved Charlene had been raped before she was killed. Both were bludgeoned to death with a piece of firewood taken from a stack outside their bedroom door.

"This 1980 murder has long been a source of fear and angst in the neighborhood in which it occurred, in the community and indeed in Ventura County," said Gregory Totten, the Ventura County District Attorney. "It also as we know was a source of great frustration for law enforcement over a prolonged period of time."

Speth has long been an advocate for thorough investigation by medical examiners, and has been one of the loudest voices calling for reform to the New Jersey Office of the Medical Examiner, which has languished due to lack of funding.

A former Gloucester County Medical Examiner, Speth was featured in Death and Dysfunction, an 18-month NJ Advance Media investigation into the state medical examiner system. It led to comprehensive reform moving swiftly through the state legislature, and it now sits on the desk of Gov. Phil Murphy, who himself called for wholesale reform after the NJ Advance Media media investigation was published in December.

Speth believes the creation of a duplicate rape kit, which he said remains a rare practice, was key to preserving the evidence needed to connect DeAngelo to the case. Nearly 40 years later, he's now preparing to testify in the upcoming trial.

"This will give, finally, closure to the families after all these years," he said.

Stephen Stirling may be reached at sstirling@njadvancemedia.com. Follow him on Twitter @sstirling. Find him on Facebook.