EVERETT — On the day she would have turned 20, the people who loved Bridgette Johns expect to gather in a courtroom and watch sentencing for the man found responsible for her 2009 death.

Joshua Marlo Knox, 27, was convicted Wednesday of controlled-substances homicide and heroin delivery. The Mountlake Terrace man faces up to a decade behind bars.

The verdict came after two days of testimony before Snohomish County Superior Court Judge Kenneth Cowsert.

Knox opted not to have a jury hear the case, leaving it up to the judge to weigh the evidence. Cowsert announced his verdict on Wednesday afternoon.

There was a moment of awkwardness when the lawyers agreed to schedule sentencing for Feb. 22, then realized it was Johns’ birthday. Her mother, Ruth Spesshardt, assured them it wasn’t a problem.

“I want it on her birthday,” she said.

Johns was 18 when she died on Dec. 10, 2009. She knew Knox, and called him to arrange a ride from Seattle to Snohomish County. Knox had been in the city that day purchasing heroin, the judge found.

Johns had struggled with drugs but quit using heroin after her boyfriend overdosed. That day, though, she took Knox up on his offer to share his heroin.

Cowsert’s findings tracked closely with the evidence deputy prosecutor Mark Bridges detailed in court papers.

Johns fell asleep after taking the drug. Twice later she woke up, complaining that her ears were ringing and that something was wrong.

Knox told detectives he told Johns to go back to sleep. Later he was awakened by what he took to be loud snoring. Experts testified the noise likely was Johns entering drug-induced respiratory distress.

Johns was barely breathing, if at all, when Knox awoke around 11 a.m., saw her condition, and called 911, Cowsert found.

The autopsy determined Johns had used marijuana, cocaine and heroin. The county’s medical examiner, Dr. Norman Thiersch, testified her death came as a result of drug overdose.

Cowsert said testimony from a state toxicology expert convinced him that the other drugs present weren’t key to the case, and that Johns’ life ended from lethal exposure to heroin. Knox supplied the drug, he ruled.

Before announcing his verdict, the judge apologized to Johns’ family for revisiting painful testimony.

“This has been a tragedy, and I don’t intend to increase the pain and suffering more than I have to,” he said.

Scott North: 425-339-3431; north@heraldnet.com.