A Massachusetts woman who goaded her boyfriend into killing himself with numerous text messages and phone calls has lost her bid to appeal her manslaughter conviction in the US Supreme Court.

Key points: Michelle Carter was convicted of involuntary manslaughter in 2017

Michelle Carter was convicted of involuntary manslaughter in 2017 She was found to have coerced her boyfriend to take his life via thousands of text messages and phone calls

She was found to have coerced her boyfriend to take his life via thousands of text messages and phone calls The US Supreme Court declined to hear an appeal against her conviction

The justices refused to hear Michelle Carter's appeal of a Massachusetts Supreme Judicial Court ruling last year upholding her 2018 conviction.

Evidence in the trial showed Carter repeatedly urged her boyfriend, Conrad Roy, to take his life in 2014.

She was 17 and he was 18 at the time.

Carter's lawyers argued her conviction violated her right to free speech under the US constitution's first amendment.

Civil liberties advocates also raised concerns about the case.

It was the first time Massachusetts brought manslaughter charges related to texting.

Carter sentenced to 15 months in prison

In thousands of text messages, Carter encouraged Roy to "promise" to kill himself and helped him plan the event after he abandoned earlier suicide attempts.

"You just need to do it Conrad. The more you push it off, the more it will eat at you," she wrote in one text to him.

"You just gotta do it babe, you can't think about it," she wrote in another.

"You're just making it harder on yourself by pushing it off, you just have to do it," she wrote in another.

Carter was indicted in 2015.

Authorities discovered thousands of exchanges between Carter and Mr Roy. ( AP: Faith Ninivaggi/The Boston Herald )

She opted against a jury trial, leaving her fate in the hands of Bristol County Juvenile Court Judge Lawrence Moniz, who found her guilty of involuntary manslaughter in 2017.

Moniz subsequently ordered her to serve 15 months of a two-and-a-half-year sentence in prison. She started serving her sentence after the appeals court ruling.

Reuters