Michelle Koski turned 17 in the summer of 1990. She only got 11 days of being 17 before her life was violently cut short.
“Her birthday was on August 9,” Michelle’s best friend, Melissa Johnson, told Dateline. “Days later, she was gone.”
Melissa met Michelle at school at Northgate Elementary School when they were just nine years old. The next year, Michelle asked her schoolmate a very important question.
“I still remember it like it was yesterday,” Melissa said. “One day she just came up to me and said, ‘I need a best friend. Do you wanna be best friends?’ We were inseparable after that.’”
Throughout their teenage years, the pair spent their time hanging out, playing cards, having sleepovers and talking about boys. Melissa added that her best friend’s favorite card game was Rummy and that she loved Slurpees.
Even when Michelle skipped a grade and was transferred to the Summit K-12 alternative school nearby for her studies, the two girls stayed close.
“She was super smart,” Melissa told Dateline. “She wanted to be a lawyer. She was not only book smart. She was street smart. She would have made an awesome lawyer.”
But Michelle never got that chance.
August 20, 1990 was the last time Melissa spoke to her friend.
Melissa said Michelle had told her she was planning to move out of her boyfriend’s apartment in Lake City, Washington and was excited to spend more time with Melissa.
“But that was the last time I ever spoke to her,” Melissa said. “It was the last time anyone spoke to her.”
According to Detective Jim Scharf with the Snohomish County Sheriff’s Department, Michelle was dropped off by a friend at the apartment she shared with her boyfriend in Lake City on August 18. Two days later, on August 20, Michelle got a ride from the apartment to a space about 14 miles away in Snohomish County where teenagers were known to hang out, drink and ride motorcycles.
“We believe that Michelle was brought out to the space to hang out, party, drink, but then things took a terrible turn,” Det. Scharf told Dateline.
Five days later, Michelle’s body was found by a woman walking her dog in a wooded area near Highway 522 and Echo Lake Road in the southeast part of Snohomish County - close to the popular party spot.
Detective Scharf told Dateline that investigators think someone at the hangout on August 20 tried to have sex with Michelle and when she resisted, she was beaten and strangled. He added that he’s convinced Michelle knew her killer, because of the violent nature of the crime.
“There was a pile of concrete that had been broken up and dumped in that area where she was found,” Det. Scharf said. “The killer came and got a piece of that concrete and used it to finish her off.”
Michelle’s body was identified a few days later after a review of her dental records. The county medical examiner's office said she had been strangled.
There is one piece of the puzzle that Det. Scharf hopes will lead to an answer in Michelle’s case: The killer left DNA behind that has been used to narrow the search.
But after 30 years of ruling out persons of interest, including Michelle’s boyfriend, the friend who gave her a ride, and a serial rapist in the area, Det. Scharf said that while there hasn’t yet been a match, he hasn't given up on the case.
“This is something we’re hoping to solve soon,” the detective told Dateline. “We’re constantly working on it and encourage anyone with information to come forward. Someone out there knows something.”
In 2005, the Snohomish County Sheriff’s Department formed a cold case unit to focus on cases like Michelle’s. In 2008, the Snohomish County Sheriff’s Office Cold Case Unit created a deck of playing cards, the first in Washington state, and distributed them to inmates. Each card features the photo and brief summary of a cold case in the area. Michelle is featured on the five of diamonds.
Detective Scharf told Dateline their cold case unit has solved about a dozen cases with help from the playing cards and expects Michelle’s case to be another one.
“We’ve got good hope that we can solve her case,” Detective Scharf said.
Michelle’s aunt, Sonja Alderson, told Dateline their family and friends have been hoping and praying for decades for answers.
“She deserves justice,” Sonja said. “It’s been three long decades and there’s still no answer about who did this to her.”
Sonja’s brother was Michelle’s father. For years, he searched for answers in Michelle’s murder. He died in 2000, without ever getting answers. Six months later, Michelle’s grandmother also died.
“It’s heartbreaking,” Sonja said. “And it’s time for closure.”
Michelle’s best friend, Melissa, moved away and now lives in Nevada where she works as a 911 dispatcher.
“It’s weird to think that Michelle has been gone now longer than she was alive,” Melissa told Dateline. “But she’s always with me. She’s my guardian angel.”
Melissa recalls that summer and the year after being a very traumatizing time in her life.
“I was just starting my senior year and my best friend was murdered,” Melissa said. “Everything changed. It took a long time for me to recover.”
Although 30 years have passed, Melissa said she’s still hopeful the case will be solved.
“We all want, more than anything, for this to be solved,” Melissa said. “I know Detective Scharf is dedicated to this case and that’s what it’s going to take - passion.”
She added that she’ll continue to tell Michelle’s story to encourage those who may have information to come forward.
“She hasn’t been forgotten and that’s huge,” Melissa said. “We can’t give up now.”
Anyone with information about Michelle’s case is asked to call the Snohomish County Sheriff’s tip line at 425-388-3845.