In announcing his decision, Massachusetts Juvenile Court Judge Lawrence Moniz described Carter's behavior three years ago, when she was 17 years old, as "reckless." Her then-boyfriend, Conrad Roy, was 18 years old when he died in July 2014 of carbon monoxide poisoning after locking himself in his truck following the texts from Carter, including one telling him to get back in the car when he got out. Before his death, Roy had searched online for ways to commit suicide, a digital forensic analyst testified in the trial, and he had a history of previous suicide attempts, according to The New York Times.
Carter's case is the first of its kind in which someone has been convicted of manslaughter for using his or her words, First Amendment experts told ABC News.
Involuntary manslaughter is defined as an unintentional killing resulting from recklessness or criminal negligence.
Here's what experts had to say about the ruling and the First Amendment:
Carter's texts 'abhorrent' but were they criminal?
Under the First Amendment, speech cannot be criminalized, except in situations where the speech itself is a crime, such as hate speech or solicitation, Longwood, Florida-based First Amendment attorney Lawrence Walters told ABC News. Walters added that the prosecutors in Carter's case essentially tried to criminalize her words and speech.
Walters said that while "there's no question" that the speech used in Carter's texts was "abhorrent," there's no statute that says you can't encourage someone to commit suicide.
"The First Amendment is there to protect vile and repugnant speech," he said.
The ACLU said in a statement that Carter's conviction "exceeds the limits" of criminal law and "violates free speech protections by the Massachusetts and U.S. Constitutions."
"Mr. Roy's death is a terrible tragedy, but it is not a reason to stretch the boundaries of our criminal laws or abandon the protections of our constitution," said Matthew Segal, legal director of the ACLU of Massachusetts.
Massachusetts does not have a law making it illegal for someone to encourage or persuade an individual to commit suicide, Segal added.
Did Carter's texts incite Roy's suicide?
Prosecutors argued that Carter was reckless when she told Roy to get back in the vehicle, saying that Roy didn't want to die, and therefore Carter caused his death.
Marc John Randazza, free speech attorney and president of the First Amendment Lawyers Association, disagreed with the ACLU, saying that the First Amendment "does not simply say that if words are involved, you cannot be held responsible for their consequences."
"That's not how it works," he said. "If that's how it works, how would we ever have the crime of extortion? Extortion is always made of words unless you're really good at inferring what you're gonna do to someone."
Randazza cited the 1969 Supreme Court decision in Brandenburg v. Ohio, which states that speech can be prohibited if it is directed at inciting or producing imminent lawless action" and if it is likely to incite or produce such action.
Randazza said that if there is "clear and present danger of imminent lawless action, and you incite that action, and you know that your incitement will cause that action, you can be held liable for that."
He added that Carter's case isn't different from standing next to a suicidal person on a bridge and encouraging them to jump.
Were Carter's texts taken out of context?
Another issue with Carter's conviction is that prosecutors may have taken her texts out of context by not taking every text into consideration, said First Amendment attorney Jennifer Kinsley, a law professor at Northern Kentucky University.
Kinsley said she read through all of the texts Carter sent to Roy and that their meanings were "all over the place."
"In previous texts, she was encouraging the young man to get help and seek counseling and to not commit suicide," she said. "I think the messages that were used to convict her were pulled out of context."
Speech is to be taken into consideration as a whole, Kinsley said, adding that she believes that was not done in Carter's case.
"This is a very dangerous case in terms of the right of free speech," she said.
Randazza feels that Carter "obviously had no idea how to deal with mental health issues" and speculated that she became "exasperated," which led her to encourage Roy to get back in the truck.
What does this ruling mean for the future?
Carter's conviction could have a "very disturbing" and "chilling effect" on free speech, Walters said.
"A condition like this will scare people from speaking their mind -- having a conversation or robust debate -- out of fear that their words will encourage someone to commit criminal behavior," Walters said.
Walters called the ruling a "slippery slope" that may encourage prosecutors and law enforcement to apply laws across the country to criminalize speech.
The ACLU said that if the conviction is "allowed to stand," it could impede "important and worthwhile end-of-life discussions between loved ones across the Commonwealth."
Could there be a trend toward a harmed-based interpretation of the First Amendment?
Rather than the historical categorization of the First Amendment, which looks at the speech itself, courts may be trending toward a harm-based interpretation of the First Amendment, which is about how someone may feel when hearing speech, Kinsley said.
Even in cases of slander, the "categories have never been defined by the feeling of the listener," she added.
Carter's case could also have an effect on how cyberbullying on social media is dealt with in the future, Randazza said.
"In the social media age, we are seeing cases like this -- where the emotional harm of the person is being used to define the extent of free speech protection," Kinsley said.
If someone were to commit suicide as a result of online bullying, prosecutors may try to "shoe-in" on the person who did the cyberbullying for manslaughter, Randazza said.
Could Carter's conviction be reversed?
Carter maintained her innocence throughout her trial, and her lawyers argued that Roy was on the "path to take his own life for years."
Both Walters and Kinsey said it is likely that the ruling will be reversed on appeal.
"If the traditional First Amendment analysis is applied, the case should be reversed," Walters said.
"It's a pretty clear First Amendment violation for this young woman to be convicted," Kinsley said.
ABC News' Emily Shapiro contributed to this report.