'She has no conscience': Dead teen's mother attacks the girl who talked him into suicide

The mother of the US teen that took his life after encouragement from his girlfriend said Michelle Carter “knew exactly what she was doing” when sending text messages willing him on.

Carter, 20, was convicted of involuntary manslaughter for her role in the death of Conrad Roy III who died of carbon monoxide poisoning in his pick-up truck in a Massachusetts parking lot in July 2014.

“I think she needs to be held responsible for her actions ’cause she knew exactly what she was doing,” Conrad Roy's mother Lynn told CBS.

“She knew exactly what she was doing and what she said.”

Ms Roy also said that she doesn't think Carter has a "conscience."

Lynn Roy said Carter knew what she was doing when she told her teenage son to kill himself.

“The fact that she would say to him, ‘Your family will get over you.’ How is that even? - I will never get over him,” she said.

When asked how she would describe what Carter did, Lynn was unable to find the words, saying, “I cannot. Only she can.”

Carter's sentencing for what has been described as an "unprecedented manlaughter" will take place on August 3, where she faces up to 20 years in prison.

Michelle Carter's text messages are displayed in court. Picture: AP

Carter's text to friend proved telling

Roy killed himself in 2014 after Carter sent him hundreds of texts encouraging him to do so.

In the end, the main messages that sealed Carter's fate was not sent to Roy but to her friend Sam Boardman, two months after her then-boyfriend’s suicide.

“Sam, his death is my fault like honestly I could have stopped him,” Carter wrote.

Michelle Carter listens as prosecutor Maryclare Flynn makes her opening statement. Picture: AP

“I was on the phone with him and he got out of the car because it was working and he got scared and I (expletive) told him to get back in Sam.

“I knew he would do it all over again the next day and I couldn't have him live the way he was living anymore I couldn't do it I wouldn't let him.”

While Massachusetts Judge Lawrence Moniz was explaining his decision (Carter waived her right to a jury so he decided her fate alone), he said it was the texts Carter sent that acknowledged she knew how much Roy could hurt himself that rendered her guilty.

If you are concerned about the mental health of yourself or a loved one, seek support and information by calling Lifeline 13 11 14, Mensline 1300 789 978, or Kids Helpline 1800 551 800