The man dubbed the “I-5 Strangler” has pleaded guilty to six murder charges, including two cases that occurred in Napa County, following court proceedings in San Joaquin County.

Roger Kibbe, 70, accepted a plea agreement Sept. 29 that included two life sentences without the possibility of parole, according to San Joaquin County District Attorney James Willett.

In 1991, Kibbe was convicted of the 1987 strangling of a West Sacramento woman, Darcie Frackenpohl. He was sentenced to 25 years to life in prison.  He also became a key suspect in other murders in San Joaquin, Sacramento and Napa counties between 1977 and 1986, the Napa County district attorney’s office said.

He confessed in 2003, when investigators questioned him about those cases.

Last year, Kibbe was indicted in the murders of six women, including Walnut Creek resident Lou Ellen Burleigh, 21, and Sacramento area resident Katherine Quinones, 25. Kibbe brought both Burleigh and Quinones to the Lake Berryessa area before he killed them, according to prosecutors.

In September 1977, prosecutors said Kibbe lured Burleigh to a business park one Sunday morning under the pretense that he was looking to hire a secretary. Burleigh disappeared and was reported missing later that day.

Kibbe told investigators during his confession that he kidnapped her and drove to Napa County, where he killed her. Burleigh’s body was never found.

No one in Napa County knew of the murder until Kibbe confessed in 2003, said Mike Frey, now supervising investigator at the Napa County district attorney’s office.

Frey was a detective at the Napa County Sheriff’s Office in 2003 and was assigned to assist San Joaquin County with its investigation. Kibbe’s confession led Frey to check the missing person’s cases in Walnut Creek, where he found Burleigh’s name.

In 1986, Kibbe picked up Quinones and drove her to Lake Berryessa.

Quinones’ body was found near the Pope Creek Bridge a few months later by people playing Frisbee in the area.

Napa County District Attorney Gary Lieberstein agreed to have San Joaquin County prosecute the case under a law that allows one county to prosecute homicide cases that cross multiple jurisdictions, he said.

Fibers and other microscopic evidence processed by the California Department of Justice linking Kibbe to the crimes were present in most of the cases. Officials agreed they could present the strongest case if all were combined, Lieberstein said.

He said cases like Kibbe’s are also very time-consuming and require  more staff and money.

 “If possible, you want to avoid multiple trials in multiple jurisdictions,” he said.

Frey said Kibbe had been a suspect in several unsolved murders in the ‘80s, and investigators persisted until they got a confession during the interview from prison in 2003.

Frey was one who talked to Kibbe, who described the area where he killed Burleigh. Frey visited the area based on Kibbe’s account, but to no avail.

Frey described Kibbe as “unassuming.”

“He doesn’t look like the horrible monster that he is,” he said.

Ultimately, the San Joaquin County district attorney’s office didn’t seek the death penalty because of Kibbe’s age, the length of time it would likely take before he was executed, and the wishes of the victim’s families, Lieberstein said.

Lieberstein said he supported that decision, calling it “pragmatic.”

As part of the agreement, Kibbe consented to help investigators look for Burleigh’s remains once more, said Napa County Sheriff’s Capt. Tracey Stuart.

Kibbe accompanied sheriff’s detectives to the area last weekend, but was unable to pinpoint a location, she said.

That will likely be the last time detectives makes an effort to look for Burleigh, Frey said.

Frey’s feelings about the outcome of the case are mixed.

“On one hand, I’m happy for the families (of the victims), but I’ll always regret not being able to find Lou Ellen Burleigh’s remains,” he said. “I’m hoping someday someone will stumble across something ... I think her family deserves that.”