(CNN) -- Attorneys for Michelle Carter, the woman convicted of involuntary manslaughter in her boyfriend's suicide, have filed an appeal, saying her texts encouraging the teenager to kill himself were protected free speech.
"Because the judge convicted Carter for what she said, or failed to say, not what she did, this case implicates free speech under the 1st Amendment and art," the attorneys wrote.
"Carter's words encouraging Roy's suicide, however distasteful to this Court, were protected speech," they added.
Carter was found guilty in June 2017 on the basis of a series of texts to her 18-year-old boyfriend, Conrad Roy III, that pressed him to die by inhaling carbon monoxide in his pickup.
The disturbing texts showed that when Roy hesitated, Carter emphatically told him to go through with the suicide.
"I thought you wanted to do this. The time is right and you're ready, you just need to do it! You can't keep living this way," she wrote in one exchange.
Carter was sentenced to 15 months in jail but is currently free pending an appeal.
The case touched on issues of suicide among teenagers as well as the legal gray area of whether someone can be convicted for another person's decision to kill himself. In their appeal, Carter's attorneys said the conviction went too far in criminalizing a defendant who was not even present at the scene.
"Massachusetts would be the only state to uphold an involuntary manslaughter conviction where an absent defendant, with words alone, encouraged another person to commit suicide," the attorneys wrote.
They said Carter deserves to be acquitted or have a new trial, as her text messages were protected speech and contradicted by physical evidence. The attorneys said the judge failed to evaluate her conduct under the standard of a "reasonable juvenile."
They also argued the conviction violated her First Amendment right to free speech. Any law or crime statute that restricts speech must survive strict scrutiny and be narrowly tailored to avoid violating free speech. The law for involuntary manslaughter, the attorneys argue, is written too broadly.
"A criminal law that penalizes a person who encourages another person to commit suicide cannot survive strict scrutiny," they wrote.
Eric Goldman, an attorney for the Roy family, declined to comment on the appeal.