Michelle Carter, a teen who stands accused of encouraging her boyfriend through text messages to kill himself, is due back in court for a pretrial hearing Monday.

Carter, 18, is facing manslaughter charges in connection with the 2014 death of Conrad Roy III, who committed suicide by inhaling carbon monoxide. Prosecutors claim that Carter sent Roy dozens of messages encouraging him to follow through on his suicide plan.

Roy and Carter met in person once - in Florida in 2012 - and the two began dating. For the next three years afterward, the couple conducted their relationship entirely over text messages online.

Roy had a history of issues with depression and spent time in mental institutions in Worcester and Brookline. Following a stay in a Brookline facility, Roy attempted suicide.

Roy had told a girl he met in treatment that he was attempting suicide, prompting her to call 911. His life was saved by emergency responders, and prosecutors claim that Roy's life changed after that day.

"He told his mother he 'would never do that to [her] again,' and never again mentioned wanting or trying to take his life to her," prosecutors wrote in a court filing released in April.

On the day of his death, Roy spent the day walking the beach with his family and bought his sisters ice cream. He and his mother discussed his plan to attend the same college as his best friend and one day take over the family business.

However, while Roy spoke with his mother, he was simultaneously texting Carter about his plan to kill himself. Roy's mother told New York Magazine he was distracted by his phone for much of the walk.

At 4 a.m., Carter wrote to Roy, "You said you were gonna do it. Like I don't get why you aren't. So I guess you aren't gonna do it then. All that for nothing."

In the pretrial hearing Monday, Carter's lawyer is likely to make additional arguments defending her actions.

Earlier in the month, Carter's lawyer asked a judge for funds to hire an expert that could explain the effects on an antidepressant that both teens were taking. The judge denied that request.

In a defense brief, Carter's lawyers contested the claim that Carter was responsible for Roy's death, arguing the government had overcharged Carter to compensate for a lack of applicable law against encouraging suicide in Massachusetts.

"Charging her with manslaughter was a transparent effort calculated to circumvent the fact that the legislature has not criminalized words that encourage suicide," the brief argued.

Prosecutors are likely to argue that Roy might still be alive today if not for Carter's words.

"Unbeknownst to his mother or any of the other people he was close to, for at least the past six days Conrad had been making plans to kill himself with carbon monoxide," prosecutors said wrote in a court filing released in April. "Carter played an instrumental role: she talked him out of his doubts point-by-point, assured him that his family would understand why he did it, researched logistics and reassured him that he was likely to succeed, and pushed him to stop procrastinating and get on with it, mocking his hesitation and threatening to get him help if he did not carry through with his plans."