A woman who sent her boyfriend a barrage of text messages encouraging him to kill himself has been convicted of involuntary manslaughter.
A juvenile court judge found that Michelle Carter caused the death of Conrad Roy III.
Carter cried as the judge explained his reasoning.
She was 17 when she sent Mr Roy dozens of messages urging him to take his own life. The 18-year-old was found dead of carbon monoxide poisoning in his truck in Fairhaven, Massachusetts, in July 2014.
Prosecutors said Carter also told Mr Roy to "get back in" when he got out of his truck.
Her lawyer argued Mr Roy had a history of depression and suicide attempts and was determined to end his life.
Her sentence could range from probation to 20 years in prison.
Sobs broke out throughout the courtroom when the verdict was announced.
The judge ruled that Carter, now 20, can remain free on bail but ordered her not to make any contact with Mr Roy's family or leave the state.
The sensational trial in Taunton offered a window into teenage depression and suicide through text messages and Facebook.
"I thought you wanted to do this. The time is right and you're ready, you just need to do it!" Carter wrote in one message.
Carter's lawyer, Joseph Cataldo, said she initially tried to talk Mr Roy out of it and urged him to get professional help, but eventually went along with his plan.
An involuntary manslaughter charge can be brought in Massachusetts when someone causes the death of another person when engaging in reckless or wanton conduct that creates a high degree of likelihood of substantial harm.
Peter Breggin, a psychiatrist giving evidence for the defence, said Carter was a "very troubled youngster" who suffered from depression.
At the time of Mr Roy's death, she was taking Celexa, an antidepressant Dr Breggin said targets the brain's frontal lobe, which controls empathy and decision-making.
Dr Breggin said she was in the grips of a "grandiose" delusion that she alone could help Mr Roy find his way to heaven and she would care for his family.
Prosecutors focused on a series of text messages she sent him in the days before he killed himself.
"You can't think about it. You just have to do it. You said you were gonna do it. Like I don't get why you aren't," she wrote on the day of his suicide.
Prosecutors argued the text messages support their claim that Carter caused Mr Roy's death by recklessly helping him poison himself.
They met in Florida in 2012 while visiting relatives, and their relationship largely consisted of text messages and emails.