BOSTON — The Massachusetts Supreme Judicial Court has affirmed the manslaughter conviction of Michelle Carter, who coerced her boyfriend via text messages to commit suicide.

Carter, 22, of Plainville, was convicted of involuntary manslaughter in June in the death of Conrad Roy III, of Mattapoisett. She was sentenced to 2 1/2 years in prison with 15 months to serve with five years of probation.

Carter's defense lawyers appealed the conviction, presenting their case to the SJC in October.

In its ruling Wednesday, the Supreme Judicial Court found 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."

Roy was found dead in his truck of carbon monoxide poisoning in the Fairhaven K-Mart parking lot in July 2014. He was 17 years old.

An investigation into Roy's death revealed that Carter had encouraged him to kill himself even when he expressed second thoughts about suicide. Carter told Roy to "get back in" the truck as it filled with carbon monoxide from a generator that Roy had placed in the cab of the truck.