Teen who allegedly urged boyfriend to kill himself researched the 'best way'

New texts in a shocking case where a US teen is accused of coaxing her boyfriend to kill himself have emerged, this time showing she allegedly helped him research the 'best way' of doing it.

Conrad Roy III, 18, had driven to a K-Mart store in Massachusetts, the United States, with the intention of killing himself.

Roy was having second thoughts and stepped out of the car to contact his friend Michelle Carter, 18, but her response allegedly read: "Get back in".

His body was found in his vehicle in July 2014.

'Tonight is the night': Michelle Carter allegedly encouraged teen's suicide. Photo: AP
'Tonight is the night': Michelle Carter allegedly encouraged teen's suicide. Photo: AP

Over 1000 text messages had been exchanged between Carter and Roy in the week prior to his death.

Carter consistently urged Roy to kill himself in those messages, police have alleged. She had also questioned why he had not killed himself yet, Fairhaven Neighbourhood News reported.

In the newly released messages Carter discussed how to make his death "painless and quick" and came up with
"back-up plans" should his initial choice not work.

Carter's lawyer, Joseph Cataldo, argued that she had not committed a crime and that she had been brainwashed by her boyfriend.

He pointed to this exchange between the young lovers.

"Let's do a Romeo and Juliet. The two of us, together, kill ourselves."

Mr Cataldo said that Carter replied: "[Expletive] no. We are not dying."

You said you were gonna do it. I don't get like why you aren't,
You said you were gonna do it. I don't get like why you aren't,

But prosecutors allege Carter sent a text message to Roy's sister on the night of his death and acted as though she did not he had killed himself even though she was allegedly talking to him while he did it.

Carter also told a friend via text message: "it's my fault, I was talking to him while he killed himself. I heard him cry in pain. I should have known. I should have done something.

After Roy's death, Carter had posted messages on social media to pay tribute to her friend, as well as organising a fundraising baseball event in his honour.

The event was to raise awareness of mental health issues. Carter reportedly publicised the event, writing: "Life can be tough, but helping others makes it easier."

The teenage girl was charged with involuntary manslaughter over the death of her friend.

A spokesman for the Bristol District Attorney's Office released a statement claiming Carter knew about Roy's suicidal thoughts.

"Instead of attempting to assist him or notify his family or school officials, Carter is alleged to have strongly influenced his decision to take his own life, encouraged him to commit suicide and guided him in his engagement of activities which led to his death," the Sydney Morning Herald reported the statement saying.

If you or someone you know is struggling with mental health contact LifeLine crisis support on 13 11 14.