But Carter's attorney painted a starkly different portrait, describing a troubled, delusional young woman who was "dragged" into the suicidal journey of a teenager, Conrad Roy III, who was long intent on killing himself when he committed suicide in July 2014.
Moniz said he will alert the clerk's office when he has reviewed all testimony and exhibits, and his verdict will be announced the following day. He gave no indication of how long that might take.
The trial could set a legal precedent on whether it is a crime to tell someone to commit suicide.
'Kicked his feet out from under him'
In closing arguments, Bristol Assistant District Attorney Katie Rayburn said Carter went from offering "words of kindness and love" to Roy at one time to aggressively encouraging him to carry out longtime threats to kill himself.
"It got to the point that he was apologizing to her. ... Apologizing to her for not being dead yet," Rayburn told the judge.
Roy sought Carter's support because he didn't want to die, Rayburn said. As Roy kept putting off attempts to kill himself, Carter grew frustrated.
In the end, Rayburn said, Carter "kicked his feet right out from under him" whenever he offered an excuse for not committing suicide.
The prosecutor described Roy as a "very self aware" young man who realized he needed help, as a teenager who loved his family and whose photos from family outings and motivational messages saved on his phone demonstrated his hope to get better.
Rayburn reminded the judge of text messages in which Carter said she pushed Roy to get back in the truck where he eventually died of carbon monoxide poisoning. In text messages to a friend, she described hearing his finals words and breaths on the phone.
Carter did it, the prosecutor said, out of a desperate need for attention, a desire to portray herself as a grieving girlfriend.
"She created the harm, your honor, when she told him to get back in the car, " Rayburn said. "She knew he didn't want to die. ... She wasn't going to let him live. That was her decision. "
"It's sad ... just not homicide'
Several times during defense attorney Joseph Cataldo's closing argument, Roy's mother, Lynn Roy, and his younger sister left the courtroom. Carter's parents sat behind the defense table on the other side of the courtroom.
Cataldo said Roy had been accepted into college, had a boat captain's license and possessed the intelligence to know what he was doing. Roy knowingly "dragged" Carter on his "sad journey," the lawyer said.
"The evidence actually established that Conrad Roy caused his own death by his physical actions and by his own thoughts," Cataldo said. "You're dealing with an individual who wanted to take his own life. ... He dragged Michelle Carter into this."
Carter was "overwhelmed" by his talk of suicide while at the same time dealing "with all of her baggage," including the side effects of medication for depression, according to Cataldo.
"It's sad, it's tragic," he said. "It's just not a homicide."
The defense rested its case Tuesday after testimony from Dr. Peter Breggin, who said Carter was "involuntarily intoxicated" and "unable to form intent" after switching to a new prescription antidepressant months before her boyfriend committed suicide. She even texted his phone for weeks after he died, Breggin said.
Carter, 20, is on trial for her alleged role in the death of Roy, who was 18 when he poisoned himself by inhaling carbon monoxide in his truck. She did not testify.
Prosecutors have argued that while Carter played the role of a loving and distraught girlfriend, she had secretly nudged Roy toward suicide by sending him numerous text messages encouraging him to take his own life.
A switch in drugs
Breggin said Carter had no nefarious intent but genuinely thought she was helping Roy. She had been on Prozac for years before switching to another antidepressant, Celexa, in April 2014 -- three months before Roy's death, Breggin said.
Such drugs can impair judgment, wisdom, understanding, love and empathy, he said -- especially in the adolescent brain, which is still developing and is "more susceptible to harm and all intrusions."
At the time of Roy's death, Carter was 17.
Breggin, who did not treat Carter, told Moniz that he reached his conclusions after reviewing Carter's educational records, text messages and police files and interviewed a half-dozen people who knew her.
Carter is being tried as a youth because she was a minor when her alleged crime took place.
Before age 12, Carter had seemed to be loving, caring and helpful. But as a teen she became "a very troubled youngster," Breggin said.
Carter began taking Prozac in 2011, when she was 14, after developing anorexia, Breggin said. She later transitioned to Celexa, which he said can increase suicide risk in people younger than 24 along with agitation, panic attacks, grandiosity and not understanding the trouble one is getting into.
Adverse changes also can occur when doses change, Breggin said.
Breggin testified that Carter began cutting herself between April and June 2014.
'My life's a joke'
Roy's body was found July 13, 2014, a day after his suicide in his parked truck in a Kmart parking lot in Fairhaven, nearly 40 miles from his home.
As early as October 2012, Roy told Carter he was going to kill himself and that there was nothing she could do to stop him, Breggin said. The psychiatrist said Roy made four suicide attempts before succeeding.
Over the course of many texts to Carter about depression and hopelessness, Roy spoke often of killing himself and going to heaven, Breggin said.
Roy suggested the pair should end up like Romeo and Juliet, Shakespeare's suicidal young lovers, and believed they would still be able to communicate after death, Breggin said.
'Enmeshed in a delusion'?
On Celexa, Breggin said, Carter became "involuntarily intoxicated" and began to think she could help Roy get what he wanted -- to die painlessly, to get to heaven and to help his family grieve less by understanding him.
"She is not forming the criminal intent -- 'I'm gonna harm him,'" Breggin said. "She's found a way to use her unique power to help and to help this boyfriend -- in her mind but not in his -- to not keep making mistakes and not keep hurting himself."
Assistant District Attorney Maryclare Flynn said last week that when Roy had second thoughts that fateful night, Carter told him to get back in the truck and listened on the phone while he cried out in pain and took his last breaths.
"She was enmeshed in a delusion," Breggin testified. "She was unable to form intent because she was so grandiose."
Breggin also reviewed a letter that Roy left for Carter. It said Roy was expecting to reach heaven, that he loved her, and that he thanked her for her kindness. In the letter he didn't say anything about being bullied.
A day after Roy's suicide Carter texted him, saying: "Did you do something??! Conrad I love you so much please tell me this is a joke. I'm so sorry I didn't think you were being serious Conrad please don't leave us like this," according to the text shown in court.
Prosecutor: Carter was untruthful
During cross-examination, Rayburn tried to paint Carter as an untruthful person who craved attention.
Rayburn asked Breggin to read from a "safety plan" that was given to Roy after a mental health visit. The last question on the form was, "What is the one thing that is the most important to me and worth living for?"
Breggin read back Roy's response: "My family."
At one point on Tuesday, Rayburn asked Breggin: "You formed your opinion that [Carter] was involuntarily intoxicated before you talked to a single person?"
"I try to get an impression from medical records," he said.
Rayburn also tried to pin Breggin down on the exact period of involuntary intoxication. Breggin said it started between June 29 and July 2, 2014, but he wasn't clear when it ended.
On July 15, 2014, Rayburn said Carter met with a therapist, who did not indicate that Carter had any symptoms of involuntary intoxication.