A Massachusetts woman must serve prison time after she urged her boyfriend to kill himself in a series of text and phone conversations, a Massachusetts court ruled Monday.

The court’s ruling rejected an appeal by Michelle Carter, who was found guilty of involuntary manslaughter for the 2014 suicide of 18-year-old Conrad Roy II, when she was 17.

Carter had been sentenced to 15 months in jail after her conviction but remained free during her appeal. Her defense argued that her statements and texts urging Roy forward as he contemplated suicide were covered by First Amendment free-speech protections.

The Massachusetts Supreme Judicial Court disagreed, concluding in its ruling that “the evidence was sufficient to support the judge’s finding of proof beyond a reasonable doubt that the defendant committed involuntary manslaughter as a youthful offender, and that the other legal issues presented by the defendant, including her First Amendment claim, lack merit,” in the opinion written by Justice Scott L. Kafker, The Boston Globe reports.

Conrad Roy II More

Conrad died in his pickup truck from carbon monoxide poisoning — an act Carter had supported and encouraged in exchanges that came to light after Roy’s death on July 13, 2014.

RELATED: Inside the Controversial Conviction of a Woman Who Urged Her Boyfriend to Kill Himself in Texts

Testimony at Carter’s 2017 trial revealed that Carter, who was not present with Roy at the time he died, was on the phone with him as he expressed doubts about his actions.

In finding Carter guilty, Bristol County Juvenile Court Judge Lawrence Moniz highlighted two revelations from Carter’s trial. As Roy expressed his desire to abort his fatal plan by getting out of the truck, Carter told him to get back in. Then she initially failed to tell anyone else about it.

“She did nothing,” said Moniz. “She did not call the police or Mr. Roy’s family. Finally, she did not issue a simple additional instruction [to Roy]: ‘Get out of the truck.””

Michelle Carter after being found guilty on June 16, 2017 More

The Massachusetts high court ruling picked up a similar theme.

Roy was a “vulnerable, confused, mentally ill, 18-year-old” who had stepped out of his truck as it filled with carbon monoxide, Kafker wrote. “But then in this weakened state he was badgered back into the gas-infused truck by the defendant, his girlfriend.”