A King County Superior Court jury found Gary Wade, 42, guilty of second-degree murder for the killing of Michelle Thornton, who was found dead in the closet of her Belltown apartment on Jan. 6, 2011, after her family reported her missing.
The jury reached its verdict Wednesday after deliberating for a day and a half.
Evidence at the scene suggested there was a struggle and that Thornton had been sexually assaulted, investigators said. The medical examiner determined Thornton, 43, had been strangled to death.
Footage from building security cameras, fingerprints and DNA evidence led Seattle police detectives to Wade, who is a convicted felon. He was arrested on Feb. 26, 2011.
When questioned by detectives, Wade admitted he knew Thornton as he often sold her drugs. He initially said he'd last seen her before Christmas 2010; however, when investigators confronted him with evidence, he said "when he last saw Ms. Thornton, she was dead and that he had placed her in her closet," according to court documents.
Thornton was last seen alive on Dec. 29, 2010, when she last used her debit card. Records show she made a call on Dec. 30, but failed to report to work on the same day. Her family reported her missing on Jan. 4, 2011.
Prosecutors said Wade has a long criminal history in several states including Florida, Georgia and Utah. In Washington state, he was previously convicted of making a false or misleading statement to a public servant and possession of cocaine.
Wade will face a sentence range of 154 to 254 months in prison. A sentencing hearing has not yet been set.
"Michelle Thornton was murdered in her own apartment by a killer who tried very hard to cover his tracks," said King County Prosecutor Dan Satterberg. "Thanks to diligent police work by Seattle police detectives and skillful prosecution, we were able to identify her killer and hold him accountable."