A 20-year-old Massachusetts woman is on trial for allegedly egging on her boyfriend through text messages to take his own life.
Michelle Carter, who was 17 at the time, is charged with the involuntary manslaughter of her boyfriend, 18-year-old Conrad Roy III in 2014.
Opening statements began on Tuesday morning (local time).
Roy died of carbon monoxide poisoning in his car. Prosecutors say he had second thoughts and got out, but after talking with his girlfriend who sent him a text saying "get back in", he did.
It was one of hundreds of text messages the pair exchanged in the days leading up to his death, the prosecution says.
"Don't be scared. You're finally [going] to be happy in Heaven," local media reported Carter texted Roy.
"When are you going to do it? Stop ignoring the question???? You can't keep push [sic] it off."
Carter's trial is expected to raise the question of whether a person can be charged with someone else's death if they weren't there.
Carter's defence lawyers say the teen's words are "free speech", and cannot be criminalised under state law.
In Massachusetts assisting someone to commit suicide is not considered a crime.