The supreme court of Massachusetts has upheld the involuntary manslaughter conviction of a girl who, at the age of 17, goaded her boyfriend to commit suicide in a series of text messages and phone calls. The state's highest court rejected her lawyer's arguments that she couldn't be held responsible for his death because she wasn't physically present and that prosecuting her violated her First Amendment rights.

Defendant Michelle Carter was sentenced to 15 months in prison in 2017, but the sentence was put on hold pending appeal.

It's a chilling case. Carter didn't just suggest that Conrad Roy kill himself once or twice. Text messaging records show her repeatedly urging Roy to kill himself over several days prior to his 2014 death.

Roy told Carter of his plans to acquire a portable generator or pump and use it to fill his truck with deadly carbon monoxide gas—exactly the plan he carried out days later. She repeatedly encouraged him to move forward with his plan. When Roy expressed concerns about how his death would affect his family, Carter assured him that they'd get over it.

"You're just making it harder on yourself by pushing it off, you just have to do it," Carter texted around 4:30am on the morning of Roy's suicide. "It's probably the best time now because everyone's sleeping. Just go somewhere in your truck."

Later that day, Roy drove to a local parking lot and turned on a portable water pump that filled his truck with toxic carbon monoxide gas. Phone records indicate that around this time, Roy and Carter had two 40-minute phone calls.

We don't have a record of those phone calls, but we do know what Carter texted afterwards. Weeks after Roy's death, Carter accepted blame for the death in a text message to a friend. "Honestly I could have stopped him I was on the phone with him and he got out of the car because it was working and he got scared and I fucking told him to get back in," she wrote.

The trial judge, Lawrence Moniz, concluded that Carter's actions—and particularly her decision to urge him to get back into the truck in his final minutes—was legally sufficient for a manslaughter conviction. And on Wednesday, the Massachusetts Supreme Judicial Court upheld that ruling.

Carter's lawyers argued that the trial court shouldn't have relied on her text message admitting that she told him to get back into the truck because Massachusetts law doesn't allow convictions based solely on uncorroborated confessions.

But the supreme court concluded that her confession was corroborated well enough. Corroborating evidence doesn't need to confirm every detail of a victim's confession—it just needs to confirm that a crime occurred. The fact that Roy died and Carter was in touch with him in the final minutes was enough to confirm her confession, the high court found.

The high court also rejected defense arguments that it would be unprecedented to convict Carter for manslaughter based solely on words rather than physical actions. Wednesday's opinion points to another case where a woman threatened to commit suicide. Her husband "taunted her, saying she was 'chicken and wouldn't do it,' loaded a rifle and handed it to her, and when she had difficulty firing the rifle, told her to take off her shoes and reach the trigger that way." When she followed his instructions and shot herself, the husband was convicted of manslaughter.

More generally, the court pointed out that it's not that unusual for people to be convicted of murder or manslaughter based solely on their words. A mafia boss ordering a subordinate to kill someone is only using words but can still be convicted of murder if the subordinate follows through on his instructions.

The supreme court sought to distinguish the case from the thorny issues that could arise in euthanasia cases.

"This case does not involve the prosecution of end-of-life discussions between a doctor, family member, or friend and a mature, terminally ill adult confronting the difficult personal choices that must be made when faced with the certain physical and mental suffering brought upon by impending death," the court wrote, signaling that it might reach a different conclusion in that kind of situation.