TAUNTON — Michelle Carter, the Plainville woman who urged her high school boyfriend to kill himself through a series of texts and phone calls, was responsible for his death, according to a judge who today found her guilty of involuntary manslaughter in the landmark case.

Carter, who wept as the verdict was read this morning, was on trial for the summer 2014 death of Conrad Roy III, then 18. The verdict in the case, which drew national attention, is likely to reverberate across the country and potentially reshape criminal law relating to virtual communications.

Carter, who was 17 at the time of Roy’s death, did not take the stand in her own defense. The only time she spoke during the trial was when she tearfully waived her right to a jury last week. She will be sentenced on Aug. 3.

Tried in juvenile court, Carter was found guilty as a youthful offender.

In the days leading up to his death, she had repeatedly encouraged Roy to kill himself through texts and phone calls.

In one message, Carter texted her classmate, Samantha Boardman, that she could have stopped Roy’s suicide but instead told him to finish the job.

“Sam, his death is my fault like honestly I could have stopped him,” Carter texted on Sept. 15, 2014. “I was on the phone with him and he got out of the car because it was working and he got scared and I (expletive) told him to get back in Sam because I knew he would do it all over again the next day and I couldn’t have him live the way he was living anymore I couldn’t do it I wouldn’t let him.”

That message was key to Judge Lawrence Moniz's decision, who ruled that instructing Roy to get back in the truck was "reckless and wanton conduct" that created an environment that Carter knew would cause harm.

Prosecutors argued that Carter’s texts and calls to Roy on the night of July 12, 2014, were enough to make her “virtually present” in a criminal context. That language came directly from a 2016 Supreme Judicial Court case in which the justices unanimously found that there was probable cause for Carter to be tried for Roy’s death.

To convict, Moniz had to find Carter guilty beyond a reasonable doubt. She is, he ruled today.

Bristol prosecutors Katie Rayburn and Maryclare Flynn argued that, in keeping with the SJC ruling, in this new digital age crimes can be committed even when someone isn’t physically near a victim.

“Back years ago in order to have a relationship you had to actually see somebody — or at a minimum talk on the phone. That is no longer required,” Rayburn said in her impassioned closing on Tuesday. “People fall in love via the internet and via text. People bully via text and the internet. You can encourage someone to die via text, and you can commit a crime via text.”

However, in ruling in the trial — widely regarded as potentially setting a precedent for 21st century criminal law in a social media age — Moniz cited a 200-year-old case: Commonwealth vs. Bowen, in which a prisoner "repeatedly and frequently advised and urged (a fellow prisoner) to destroy himself." The prisoner in the adjacent cell hung himself the night before he was to be executed, and the defendant was found guilty in 1816.

"The verdict represents the application of centuries old common law principles and the interplay with today's widespread use of communication through social media," said Martin W Healy chief legal counsel to the Massachusetts Bar Association in a statement. "The case will have national implications in as a clarion call that seemingly remote and distant communications will not insulate individuals from heinous acts that could rise to the level of criminal culpability. The defendant's fate was sealed through the use of her own words."

The case was closely watched by civil liberties advocates, for its ramifications regarding the application of the First Amendment.

"Mr. Roy's death is a horrible tragedy, but Ms. Carter's conviction expands Massachusetts criminal law and imperils free speech," said Matthew Segal, legal director of the Massachusetts ACLU., after the verdict.

Carter’s defense team had unsuccessfully argued that Roy’s death was a suicide, not a homicide, in a defense that revolved around issues of mental illness.

“He was suicidal in 2011, long before Michelle Carter came along. He was suicidal then,” defense attorney Joseph Cataldo said in his closing argument. “She has some significant issues herself. He’s now bringing her along on this sad journey of his.”

Cataldo also argued that prosecutors were being selective in choosing which Carter texts they accepted at face value. On one hand, prosecutors called Carter an attention-seeking liar when she texted friends about cutting herself.

On the other hand, much of the case hinged on the truthfulness of Carter’s text to Boardman, which prosecutors claimed was a moment of honesty, Cataldo noted.

The defense also claimed Carter was involuntarily intoxicated on the antidepressant Celexa at the time of the crime. Dr. Peter Breggin, a paid expert witness for the defense, argued that Carter had a propensity to be helpful that was warped by the drug.

She blindly decided to help her boyfriend kill himself while lost in an intoxicated daze, Breggin testified.

Prosecutors, however, argued that Breggin was a hired gun who has an ax to grind with the pharmaceutical industry.

After the verdict was read, Cataldo told reporters he is "disappointed" in the decision but won't comment until after sentencing.

The case was Moniz's last before retirement.