'20/20' Examines Mandy Stavik Murder and How a Cup and Coke Can Solved the 30-Year-Old Case

Mandy Stavik disappeared after she left for a run with the family dog.
Mandy Stavik as a high school cheerleader. Handout

Former neighbor Timothy Bass was convicted after a co-worker pulled his cup and Coke can from trash.

Amanda "Mandy" Stavik was just 18 when she vanished after taking the family dog for a run in Washington's rural town of Clipper. Three days later, her naked body was found in the nearby Nooksack River.

Friday's "20/20" episode revisits the disturbing case of a murdered young woman who had just started college and how the man who killed her got away with it for three decades.

"30 Years Searching," airing at 9 p.m., features Mandy's mother, Mary Stavik, the former local prosecutor David McEachran, Mandy's then-boyfriend, Rick Zender and lead detective Kevin Bowhay.

Former neighbor Timothy Bass, 51, was found guilty in July of raping and murdering Stavik. He was sentenced to nearly 27 years in prison.

The long and winding road leading to his arrest took a dramatic turn in 2017, when investigators visited Bass' workplace, asking questions about his route as a truck driver. They told employee Kim Wagner that Bass was a suspect in Stavik's killing, one of the most famous unsolved murder cases in the Northwest. 

Wagner had a daughter and empathized with a mother's anguish over losing a child. She agreed to help, even though her bosses declined, according to local media. Later, an officer called Wagner and asked if Bass ever ate his lunch in the office. He did, Wagner replied. What do investigators need?

Not long after, Wagner watched Bass throw away a plastic cup and a Coke can he had been drinking from. She pulled both from the trash, put them in a bag, and turned them over to police. 

DNA analyses showed a match. Bass was arrested on Dec. 12, 2017 and charged with rape and first-degree murder.

Genetic testing was not routinely available when Stavik was killed. In 2009, in a last-ditch effort to find a suspect, police collected DNA samples from many men in Slavik's town. Bass had quickly married and moved away after the girl's murder. 

When detectives tracked him down, he refused to submit to DNA testing.

Wagner helped solve that problem, though defense attorneys would argue at his trial that her retrieval of the cup and can constituted an illegal search. 

A jury of six men and six women deliberated just more than one day before finding Bass guilty. 

He had told investigators he was having an affair with the college freshman. Stavik was a first-year student at Central Washington University and was well-known in her neighborhood. She had graduated the previous year from high school, where she played varsity basketball and softball, as well as the flute, clarinet and saxophone. She was an honor student and a cheerleader, knew sign language and spoke Japanese. 

"She had it all going for her," a former teacher told The Associated Press in 2017. "She had a bright future ahead of her."

On the day she went for her last jog, she followed her usual route, which took her past Bass' house, investigators said. At her side was Kyra, the family's German shepherd. Hours after she left her home, as her parents grew worried, Kyra returned alone.

The Staviks called police.