Almost three years ago, Massachusetts teenager Conrad Roy III was found dead from carbon monoxide poisoning in his pickup truck in a Kmart parking lot.
His girlfriend posted grieving messages on social media and raised money in his name for mental health awareness. His friends and family lamented a young life cut short by suicide.
But before long prosecutors came up with another, more sinister, theory about what happened. And within months they indicted the girlfriend, saying they had discovered numerous text messages from her urging Roy to kill himself.
Michelle Carter, who was 17 at the time, goes on trial this week in a Taunton, Massachusetts, courtroom on involuntary manslaughter charges. She waived her right to a jury trial Monday, meaning her case will be decided by a judge who will hear testimony and render a verdict.
Boston defense attorney Peter Elikann told CNN affiliate WFXT that lawyers and legal scholars are watching the case closely because it could set a legal precedent.
"At the moment, there's really no law on the books in Massachusetts about whether somebody can encourage somebody to commit suicide or not," he said.
Carter, now 20, is being tried as a youthful offender because she was a minor when her alleged crime took place.
Opening statements are scheduled to begin Tuesday morning.
'You need to do it, Conrad'
Roy, 18, was found dead in his truck on July 13, 2014, in Fairhaven, Massachusetts. Police say he used a combustion engine to fill the cabin with carbon monoxide.
The day before, authorities say, Carter had urged him to go through with his plan to commit suicide.
"You need to do it, Conrad," Carter told Roy in a text message the morning of July 12, according to a document disseminated by the Bristol County District Attorney's Office.
"You're ready and prepared. All you have to do is turn the generator on and you will be free and happy," she reportedly wrote. "No more pushing it off. No more waiting."
According to the District Attorney's office, Roy drove that day to the Kmart parking lot, nearly 40 miles from his home. At one point, he got out of his truck and spoke to Carter for more than 40 minutes on the phone, telling her that he was having second thoughts about taking his life, prosecutors said.
But she told him to get back into the car, according to the document.
CNN has reached out for comment from Carter's legal team but has not heard back. In 2015 Carter's attorney, Joseph Cataldo, told CNN that evidence will show she had attempted to console Roy on many occasions and had advised him to seek professional help.
"My heart goes out to the family, but this was a young man who planned this for months and months," Cataldo said.
'You fall asleep and die'
In the months following Roy's death, Carter organized a charity softball tournament and raised $2,300 money for mental health awareness in his honor.
But as police investigated, they found hundreds of text messages between Carter and Roy. In one text message, Carter allegedly counseled Roy on exactly how to commit suicide using carbon monoxide.
"If you emit 3200 ppm of (carbon monoxide) for five or ten minutes you will die within a half hour," she wrote. "You lose consciousness with no pain. You fall asleep and die."
Carter was indicted in February 2015. Her trial was delayed earlier this year at the request of the defense. Youthful offenders are tried in juvenile court, but the proceedings are public.