A teenage girl who sent a barrage of text messages to her boyfriend encouraging him to kill himself has been convicted of involuntary manslaughter.

A juvenile court judge found that Michelle Carter caused the death of Conrad Roy III.

Carter, who is now 20, cried in court this afternoon as the judge explained his reasoning.

She was 17 when she sent Mr Roy dozens of messages urging him to take his own life.

The 18-year-old was found dead of carbon monoxide poisoning in his truck in Fairhaven, Massachusetts, in July 2014.

Prosecutors said Carter also told Mr Roy to “get back in” when he got out of his truck.

Her lawyer argued Mr Roy had a history of depression and suicide attempts and was determined to end his life.

Her sentence could range from probation to 20 years in prison.

MirrorOnline previously reported how Conrad had spoken about his “social anxiety from beyond the grave – via videos.

The teen, who had long battled depression was found dead in a K-mart parking lot several miles outside Boston, America.

Two videos found on the tragic teen’s computer have been played to a court, where he describes his battle with mental health issues.

In one heart-breaking clip, he reveals he’s scared that he “will never be successful, will never have a wife, never have kids, never learn.

“But I have a lot to offer someone. I’m introverted, nice and caring – that’s some benefits. I’m a nice kid. But it comes to a point where [I’m] too nice.”

Transcripts of text messages sent between the pair in the days before his tragic death has been released by Prosecutors at Taunton Trial Court, Massachusetts.

At one point Roy expressed hesitancy about his suicide plan, writing: “Like no I would be happy if they had no guilt about it because I have a bad feeling that this is going to create a lot of depression between my parents and sisters.”

She allegedly responded: “Everyone will be sad for a while, but they will get over it and move on. They won’t be in depression I won’t let that happen.

“They know how sad you are and they know that you’re doing this to be happy, and I think they will understand and accept it. They’ll always carry you in their hearts.”

Carter was accused of repeatedly encouraging him to take his own life, allegedly writing: “The time is right and you’re ready, you just need to do it! You can’t keep living this way.”

The court heard more than 20,000 text messages exchanges were made – with more than 1,000 of those messages sent in the days leading up to Roy’s death.

Carter’s lawyer, Joseph Cataldo, had insisted that no crime was committed by his client.

He said Roy had a history of depression, which involved a previous suicide attempt and was wholly responsible for his own death.

He also claimed text messages were protected by free speech laws.