Mandy Stavik was murdered in Whatcom County in 1989. Her the case went cold for nearly 30 before police made an arrest.

BELLINGHAM, Wash. — Three decades after 18-year-old Mandy Stavik was murdered in Whatcom County, her killer was brought to justice.

On Friday, a jury found Timothy Bass guilty of raping and murdering Stavik in 1989 before dumping her body in the south fork of the Nooksack River.

Jurors deliberated for just over one day before delivering a verdict.

Stavik went missing after going for a jog with the family dog on Thanksgiving Day. The dog returned three hours later, but Stavik did not. Three days later her body was found in the river. She had been hit in the head and had apparently drowned.

Bass, who lived down the road from Stavik in Deming, was arrested in 2017 several years after he became a suspect. He had refused to give police a DNA sample, but a coworker helped police get a sample off a plastic cup.

Kimberly Wagner took a Coke can Bass used at work and turned it over to police.

"When I suspected that it was Tim, I had to do the right thing for Mandy, her mom, for the community, [and] for her friends," Wagner said.

The DNA matched evidence recovered from Stavik’s body. However, Bass had claimed that he had consensual sex with Stavik several hours before she disappeared.

Bass did not testify in his own defense.

Longtime prosecutor Dave McEachran came out of retirement to try this case for free.