Under state law, the sentence was the only one possible for 52-year-old James Allen Kinney. He pleaded guilty to aggravated first-degree murder last month in Whatcom County Superior Court.
The prosecutor did not seek the death penalty.
Allen admitted killing Keri Lynne Sherlock on Oct. 3, 1998. Her body was found on a logging road about 30 miles east of Bellingham.
The 20-year-old from Braintree, Mass., had been visiting relatives while considering whether to attend Western Washington University in Bellingham.
A fugitive for two years, Kinney was arrested in March of last year in Elizabeth City, N.C. He was found through a tip generated by the television show "America's Most Wanted."
Kinney had also been wanted for questioning about unsolved killings of young women in Michigan, Minnesota, Iowa, Idaho and Oregon.
Kenney, a Vietnam veteran, has been hospitalized at least 26 times during the past 20 years for mental illnesses, including paranoid schizophrenia, schizophrenia, bipolar disorder and schizoaffective disorder, prosecutors said.
Kinney was the last person seen with Sherlock, the truck he was driving was found about a mile from her body, and physical evidence at the scene linked Kinney to the crime, according to court documents.