TAUNTON — Michelle Carter was found guilty of involuntary manslaughter Friday by a judge who ruled that the young woman recklessly goaded her boyfriend into suicide with a series of phone calls and texts, and then failed to help him.
Carter was 17 when she urged 18-year-old Conrad Roy III to kill himself in July 2014 — even after he told her he was too scared to go through with the act.
From 30 miles away, she ordered him back into a truck that was filling fast with carbon monoxide, then listened as he choked to death on the fumes. Those actions, Judge Lawrence Moniz decided, led to Roy’s death.
“She did not call the police or Mr. Roy’s family,” said Moniz, a juvenile court judge. “She called no one. And finally, she did not issue a simple additional instruction: Get out of the truck.”
Moniz declared Carter, now 20, a youthful offender, which under Massachusetts law makes her eligible to be sentenced as an adult. She faces a sentence of probation, or as much as 20 years in prison. Sentencing was scheduled for Aug. 3.
Moniz’s decision, issued from the bench before a packed courtroom in Bristol County Superior Court, ended an extraordinary trial that explored a virtual relationship between teenagers and asked whether a person’s words should make her criminally responsible for another person’s actions.
The trial, which garnered national attention, riveted lawyers and the public alike as it delved into the painful interior lives of two teenagers who called themselves boyfriend and girlfriend though they had seen each other in person only a few times.
They lived an hour away from each other — she was in Plainville and he was in Mattapoisett — but met in Naples, Fla., in 2012 while they were each on family vacations.
For the next two years, they communicated primarily through text messages and Facebook, digital communications that would provide the bulk of the evidence at Carter’s trial.
Carter showed a range of emotions Friday as Moniz explained his verdict in a booming voice from the bench.
At first, she appeared to weep with relief when Moniz started by declaring prosecutors had failed to show Carter’s many texts to Roy had led to his death.
The judge declared Roy had acted alone — and with purpose — when he secured what he would need to commit suicide.
But as Moniz continued to deliver his decision, describing all the ways Carter could have saved Roy, it became clear the defense had lost. Carter’s attorney wrapped his arm around the young woman, who shook with quiet sobs, clutching a tissue to her face.
Behind her sat her mother and father, who had worn a suit every day of the weeklong trial. The family left the courthouse without speaking to reporters.
On the other side of the courtroom was Roy’s mother, Lynn Roy, who sat among a large group of supporters, crying and wiping away tears as she listened to Moniz’s decision.
She declined to speak with reporters after the ruling. Roy’s father, Conrad Roy Jr., briefly addressed the media, thanking police and prosecutors for their work on the case.
“This has been a very tough time for our family, and we would like to just process this verdict that we are happy with,’’ he said.
The case sparked debate among legal specialists, who noted there is nothing under Massachusetts law that forbids someone from encouraging someone else to commit suicide.
Carter’s attorney, Joseph Cataldo, had repeatedly argued that Roy was a troubled young man so intent on committing suicide, he had tried to kill himself multiple times.
But each time, the judge said, Roy stopped himself, then told someone about what he had tried to do, and got help from that person.
Moniz agreed it was Roy who researched how to kill himself and obtained a generator and water pump to fill his truck with carbon monoxide.
One week before police found him dead in his pickup truck, Roy texted Carter that he was having second thoughts.
“I don’t think I have it in me,” he wrote.
“I knew it,” Carter responded.
In another text, she wrote: “Hang yourself, jump off a building, stab yourself. I don’t know. There’s lots of ways.”
Still, the judge ruled that Carter’s texts encouraging Roy to kill himself in the days leading up to the suicide did not result in his death.
It was Carter’s command during their last conversation, that Roy return to his truck — then filled with toxic fumes — and her subsequent failure to act that rose to the level of criminal behavior.
Moniz noted that Carter sent texts to friends after Roy’s death in which she said she knew that the fire and police departments were nearby, about half a mile from the Kmart parking lot where Roy had driven his truck.
Cellphone records showed a 47-minute phone call between Carter and Roy on July 12, 2014, when prosecutors said Roy attached a compression pump to his truck in the Fairhaven parking lot.
“She instructs Mr. Roy to get back into the truck despite knowing all of the feelings he has exchanged with her. All of his ambiguities. All of his fears. His concerns,” Moniz said. “Ms. Carter’s actions, and also her failure to act where she had a self-created duty to Mr. Roy because she had put him into that toxic environment, constituted wanton and reckless conduct.”
Moniz said that before finding Carter guilty, he wanted evidence confirming that Carter listened on her cellphone as Roy slowly died. He said he found that evidence in text messages Carter sent friends after Roy’s suicide in which she described hearing the loud noise of the generator in the background — and the sound of Roy coughing as he inhaled the carbon monoxide.
Moniz, who deliberated for two days, dismissed assertions that the case was novel.
He cited the trial of a Massachusetts inmate who was prosecuted in 1816 for persuading another inmate facing a death sentence to hang himself in his cell before he was executed.
He also cited the prosecution of two homeless men who accidentally started a fire inside the Cold Storage warehouse in Worcester in 1999 that killed six firefighters. Those men were indicted on charges of involuntary manslaughter but never convicted.
And he said he was not swayed by the defense argument that Carter was “involuntarily intoxicated” by prescription medication she had taken for depression in the weeks leading up to Roy’s suicide.
A psychiatrist testifying on Carter’s behalf, Dr. Peter R. Breggin, said during the trial that the medication, Celexa, coupled with a psychiatric condition, created a “grandiose’’ belief in Carter that she alone could guide Roy to heaven and take care of his family afterward.
Cataldo said Carter and her legal team were “disappointed in the verdict,” declining further comment.
Bristol Assistant District Attorney Katie Rayburn had described Carter as a manipulative bully so desperate for attention she persuaded Roy to kill himself so she could bask in the sympathy of her peers.
After the verdict, Rayburn struck a sober tone and said “there are no winners here.”
“Two families are torn apart and will be affected by this for years to come,’’ she said. “In the end, the case was really about one young man and one young woman who were brought together by tragic circumstances.”
Rayburn said Roy’s family wishes he was alive, fulfilling his dream of becoming a tugboat captain.
“The evidence clearly showed that not for the actions of Michelle Carter,” she said, “Conrad Roy would still have been alive on the morning of July 13, 2014.”
Maria Cramer can be reached at email@example.com. John R. Ellement can be reached at firstname.lastname@example.org. Globe correspondent Andrew Grant contributed to this report.