(CNN) -- A Massachusetts judge found Michelle Carter, 20, guilty of involuntary manslaughter in the 2014 death of her boyfriend, who poisoned himself by inhaling carbon monoxide in his pickup truck. Prosecutors had argued she sent Conrad Roy III, 18, numerous text messages urging him to commit suicide.
"She called no one, and finally she did not issue a simple additional instruction: Get out of the truck," Bristol County Juvenile Court Judge Lawrence Moniz said as Carter stood to receive the ruling.
"This court has found that Carter's actions and failure to act where it was her self-created duty to Roy since she put him in that toxic environment constituted reckless conduct," the judge said. "The court finds that the conduct caused the death of Mr. Roy."
The defendant, who was tried as a juvenile because of her age at the time of the crime, cried silently as Moniz spent about 15 minutes explaining the rationale for his decision before announcing the ruling. Roy's relatives, who sat near her in the first row, wept as Moniz ticked through the steps Roy took to end his life, as well as Carter's complicity.
Moniz allowed Carter to remain free on bail until her sentencing on August 3. She was ordered to have no contact with members of the Roy family. She cannot apply for or obtain a passport, nor can she leave Massachusetts without permission from a judge.
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The case was built largely on Michelle Carter's own words, in the form of hundreds of texts messages exchanged with a vulnerable young man who killed himself in July 2014 by inhaling carbon monoxide in his pickup truck.
A Massachusetts judge is due to deliver a decision Friday on whether those words were enough to convict Carter, 20, of involuntary manslaughter in the death of her boyfriend, Conrad Roy III, who was 18 when he took his life. If convicted, she could spend 20 years in prison.
The ruling could set legal precedent for whether it's a crime to tell someone to commit suicide. It may also spur lawmakers to codify such behavior as criminal.
Texts drove suicide, prosecutors argue
Carter secretly nudged Roy toward suicide by sending him numerous text messages encouraging him to take his life, prosecutors said.
In closing arguments Tuesday, prosecutors said Carter berated her vulnerable boyfriend when he had second thoughts about killing himself, listened by phone to his last breaths and used his suicide to get from friends the attention that she desperately craved.
Carter went from offering "words of kindness and love" to aggressively encouraging Roy via text message to carry out longtime threats to commit suicide, Bristol Assistant District Attorney Katie Rayburn told the court.
"It got to the point that he was apologizing to her, ... apologizing to her for not being dead yet," Rayburn said in her closing argument.
Rayburn reminded the judge of text messages in which Carter encouraged Roy to get back in the truck, where he eventually died of carbon monoxide poisoning. In text messages to a friend, she described hearing his finals words and breaths on the phone.
'Tragic ... not a homicide,' defense says
Carter's attorney argued she was a troubled, delusional young woman who was "dragged" into the suicidal journey of Roy, who has long been intent on killing himself.
"The evidence actually established that Conrad Roy caused his own death by his physical actions and by his own thoughts," defense attorney Joseph Cataldo said. "You're dealing with an individual who wanted to take his own life. ... He dragged Michelle Carter into this."
Carter was "overwhelmed" by Roy's talk of suicide while at the same time dealing "with all of her baggage," including the side effects of medication for depression, Cataldo said.
"It's sad, it's tragic," he said. "It's just not a homicide."
Earlier in the trial, a psychiatrist testified that Carter was delusional after becoming "involuntarily intoxicated" by antidepressants. She was "unable to form intent" after switching to a new prescription drug months before Roy's suicide, and she even texted his phone for weeks after he died, the psychiatrist testified.
Case watched closely
Carter's fate now rests with Bristol County Juvenile Court Judge Lawrence Moniz, who heard the case after Carter waived her right to a jury trial. She's being tried in juvenile court because she was 17 at the time of the alleged crime.
Roy's body was found July 13, 2014, a day after his suicide in his parked truck in a Kmart parking lot in Fairhaven, nearly 40 miles from his home.
Friday's ruling will be closely watched by legal experts.
"The wrinkle here is whether she coerced him or pressured him into doing something that he wasn't in a position to rationally and autonomously decide to do because he was in such a depressive state," said Daniel Medwed, professor of law and criminal justice at Northeastern University.
"It's a square peg in a round hole," he said. "It's not a perfect fit for manslaughter."