Fairplay, Colo. ? A man convicted of murder in Kansas in 1982 has pleaded guilty to killing a 24-year-old graduate student while she was working on a mapping project in a remote part of the San Isabel National Forest this summer.

Robert Amos pleaded guilty Friday and was immediately sentenced to life in prison without parole in the death of Alyssa Heberton-Morimoto. Judge Charles Barton also sentenced Amos to 60 years for a kidnapping charge and for using a deadly weapon.

Amos had earlier asked to be executed but prosecutor Molly Chilson said Heberton-Morimoto’s family opposed the death penalty.

During the hearing, Chilson explained how Amos strangled Heberton-Morimoto after encountering her in the forest, where he had been camping, on June 26.

Heberton-Morimoto’s husband sat expressionless in the court’s front row while one woman buried her head in her hands most of the time. No family or friends spoke when given a chance by the judge.

Kansas records show he was known as Dennis Cook when he was convicted of second-degree murder in 1982. He strangled an elderly music teacher with an instrument cord and left his body in the bathtub 25 years ago in Kansas City, Kan.

Amos was transferred to a Colorado prison in 1982 after agreeing to testify against a co-defendant and was paroled in 2000. He has never explained why he killed Heberton-Morimoto.

She was a summer intern for the Colorado Geologic Survey, which locates and maps such hazards as sinkholes and avalanches. She had been working with a professor on the day she was killed but they had split up for a time. The professor, Karen Houck, later heard her cries for help over her radio but couldn’t find her.

When Houck went searching for Heberton-Morimoto she ran into Amos and he offered to drive her to get help. They encountered a forest ranger on the road and Houck got out.

Amos was arrested the following day after Heberton-Morimoto’s body was found.