“We will meet someday in heaven,” Massachusetts teenager Conrad Roy III wrote in a 2014 suicide note to his girlfriend Michelle Carter, who now stands accused of pressuring him to take his own life.

The note was introduced into evidence on Tuesday (US time), before a judge heard closing arguments in the involuntary manslaughter trial.

“I love you and greatly appreciate [your] effort and kindness towards me,” Mr Roy said in his handwritten note to Ms Carter.

“This life has been too challenging and troublesome to me but I’ll forever be in your heart.”

Mr Roy also instructed Ms Carter to take “anything from my room … to remind you of me”.

A then-18-year-old Mr Roy took his own life in July 2014.

Ms Carter, then 17, was later indicted for involuntary manslaughter in February 2015 after police found text messages in Mr Roy’s phone from Ms Carter urging him to follow through with the suicide.

Ms Carter, now 20, faces up to 20 years in jail if she is convicted. Judge Lawrence Moniz will decide her fate after Ms Carter waived her right to a jury.

While the prosecution claimed Ms Carter played a “sick game” with Mr Roy’s life in order to gain attention as the “grieving girlfriend”, the defence suggested Mr Roy, who suffered from social anxiety and depression, would have taken his own life regardless.

“What we’re dealing with is a suicide and not a homicide,” defence attorney Joe Cataldo told the court on Tuesday in his closing arguments.

Conray Roy III suffered from social anxiety and depression. Photo: Facebook

Mr Cataldo said Ms Carter was “overwhelmed” by Mr Roy’s behaviour in the lead-up to his death and was suffering side effects from the medication Celexa, commonly used to treat depression.

“We’re dealing with an individual who wanted to take his own life … he accomplished what he wanted. He dragged Michelle Carter into this, Your Honour.”

But Bristol Assistant District Attorney Katie Rayburn said Ms Carter “created the harm” when she urged him to follow through with his suicide attempt.

“When he didn’t want to do it, she berated him, she repeatedly asked him why not, she became angry,” Ms Rayburn said.

“She sat on the phone after telling an 18-year-old boy to get back in the car to kill himself after he didn’t want to, and she listened to him cry on the phone,” Ms Rayburn told the judge, according to the Boston Globe.

“She sat there, Your Honour, on the phone and listened to him die.”

Much of the trial has centred on the text messages Mr Roy and Ms Carter exchanged in the weeks leading up to his death.

In one of the messages presented to the court last week, Ms Carter wrote to Mr Roy: “I thought you really wanted to die but apparently you don’t. I feel played and just stupid.”

After his death, she text messaged a friend saying Mr Roy’s death was “her fault”.

“Like, honestly I could have stopped it,” Ms Carter wrote to her friend, according to Boston Magazine.

“I was the one on the phone with him and he got out of the car because he was working and he got scared and I f***ing 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 that way the way he was living anymore.”

In the state of Massachusetts, assisting a suicide is not considered a crime, which could explain why prosecutors are pursuing an involuntary manslaughter charge.

If you are troubled by anything you’ve read in this report, help is available. Call Lifeline on 13 11 14 or beyondblue on 1300 22 4636.