A teenager in Massachusetts has been found guilty of involuntary manslaughter after a judge ruled texts she sent her boyfriend prove she was negligent during his 2014 suicide.

Michelle Carter, who was 17 when she committed the crime, was talking to her then-boyfriend via text during a suicide attempt. The New York Times reports the victim, 18-year-old Conrad Roy III, stepped out of his vehicle after he became sick from carbon monoxide fumes pumping into his truck. Carter urged him to "get back in" to his truck, and he was found dead the next day.

The judge presiding over the case reviewed extensive evidence, including thousands of text messages sent back-and-forth between the couple, and eventually ruled that Carter did little to stop Roy from putting himself in harm's way.

"She admits in subsequent texts that she did nothing, she did not call the police or Mr. Roy’s family," said Judge Lawrence Moniz. "And finally, she did not issue a simple additional instruction: 'Get out of the truck.'"

Attorneys for Carter presented evidence that showed she had helped stave off previous suicide attempts by Roy and highlighted mental and physical issues their client was dealing with in an attempt to make her a more sympathetic figure. During testimony, a psychiatrist and psychopharmacology expert, Dr. Peter R. Breggin, claimed Carter became a completely different person when she changed prescription medications in the months before Roy's death.

"She was enmeshed in a delusional system," he testified. "She’s thinking it’s a good thing to help him die."

The decision to charge Carter with involuntary manslaughter sets an extraordinary precedent, particularly for the state of Massachusetts. The state has no formal law against encouraging suicide, and in order to convict her of the crime, the prosecution was tasked with proving the texts sent by Carter effectively killed him.

Prosecutors were adamant that was the case when they addressed the judge.

"People fall in love on the internet and via text, people bully via text and the internet, and you can encourage someone to die via text," said the assistant district attorney, Katie Rayburn. "Every time he came up with an excuse not to do it, she kicked his feet out right from under him and told him why it didn’t matter, why he still needed to die."

Carter faces up to 20 years in prison as a result of the conviction.