Often, a criminal trial is a contest over a competing set of facts.

But the case of the Commonwealth of Massachusetts versus Michelle Carter, charged with involuntary manslaughter of Conrad Roy for allegedly encouraging him to commit suicide, does not quite fit that mold.

For one thing, most of the facts of Conrad’s suicide have not been disputed – and the case may ultimately hinge on Carter’s intentions, motivations, and the perplexing nature of the relationship between Michelle Carter and Conrad Roy – a relationship that does not appear, after two days of testimony, to match the easy “Girlfriend/Boyfriend” characterization that media accounts have proliferated.

But Carter’s defense also hopes to turn the prosecution’s narrative on its head.

Carter’s lawyers will try to show that Roy’s own mental health struggles were deep-seated and that Roy had contemplated and even researched suicide long before he even met Michelle.

And they will likely offer evidence that rather than a heartless exploiter of Roy’s troubles, Carter was a fellow sufferer: a teenager who had struggled herself with mental health issues, who had sought to help and support Roy while seeking medical help for her own problems, and who may have been experiencing adverse reactions to psychotropic medications when she sent the infamous text messages.

The case has been widely characterized as putting on trial the legal limits of digital bullying – and it may turn out to be just that.

But it may yet turn out to revolve around hazier issues, including the tricky lines between the agency, culpability, and moral responsibility of young people as they try to navigate confusing, difficult and sometimes disappointing paths towards health.

To Recap: Carter, who lived in Plainville, and Roy, who lived in Mattapoisett, happened to meet while both were in Florida. Carter was 17 and Roy was 18.

They struck up a relationship that was mostly or almost entirely conducted by phone and text message.  

They would talk about Roy’s struggles with depression and suicidal thoughts. When Roy’s thoughts turned again to suicide in the summer of 2014, Michelle Carter sent him various text messages seemingly encouraging him, like:  

·       “When you going to do it? Stop avoiding the question”

·       “You better not be bullshitting me when you say [you’re] going to do that.”

·       “You need to do it … you promise?”

When, on July 13, 2014, Roy got into his truck and began to pump carbon monoxide into the vehicle, Carter was apparently on the phone with him, encouraging him to go through with it – and even telling him to get back into the truck when Roy, apparently having second thoughts, confided over the phone that he’d gotten out of it.

Carter apparently stayed on the phone with Roy when he did get back into his truck until he was no longer responsive.

Roy was found dead in a parking lot in the nearby town of Fairview, Massachusetts. Carter has been charged with involuntary manslaughter and could face up to twenty years in prison if convicted.

The Prosecution’s Case: Bristol County prosecutors say that Carter should be convicted because she knowingly and willingly contributed to and encouraged Roy’s death by suicide.

But with Carter’s copious and seemingly-damning text messages already accepted as evidence in court, that’s not the extent of the prosecution’s case.

Carter, prosecutors say, had a motive: To gain attention, sympathy, and popularity from her peers, who she felt didn’t otherwise like her or want her friendship.

Carter, the prosecution says, wanted to bask in the attention of playing the role of the “grieving girlfriend,” and encouraged Roy’s suicide to accomplish that goal.

The Defense: Lawyers for Carter have yet to present their full case.

But in opening remarks, Carter’s attorney, Joseph Cataldo, outlined two main defenses -- neither denying that Carter had sent the infamous text messages, but arguing instead that Carter committed no crime and that she is not the monster depicted by the prosecution.

Cataldo focused first and foremost on a simple argument: Roy’s death, he said, was a tragic case of suicide; “But not a homicide.”

Roy, he argued had been suffering from depression and/or other mental health challenges for years – sine long before he met Michelle Carter.

Roy had spent years trying various medicinal remedies for his depression to little avail That was one reason, Cataldo said, that Roy had already been contemplating suicide.

But Cataldo also suggested that his defense of Carter will also show that Carter herself was struggling with various mental health issues. Carter, the defense has suggested, was herself adjusting to anti-depressant medications that may have affected her behavior.

While the prosecution has made strong use of text messages and other communications that occurred in the days and weeks around Roy’s suicide, the defense argues that it will show that Carter in fact tried to help Roy with his struggles, at times recommending that he seek professional help when he was reluctant.

Is it a crime to be a bad person? For all the shocking depictions of Michelle Carter presented so far – and they are many– the legal foundations of this case may be far less sensational.

Carter is not, after all, being tried for being a bad person; nor is she being charged with “bullying.”

Instead, the case rests on whether Carter’s actions, even if deplorable, rise to the level of involuntary manslaughter – direct responsibility, in other words, for Roy’s death.

It was this point to which Carter lawyer Cataldo returned again and again in his opening remarks.

Roy ultimately made the decision, Cataldo said.

It was, he said a “tragic suicide.”

“But this is not a homicide.”

The case of Commonwealth v Michelle Carter is ongoing. Follow WGBH News and @isaiah_thompson for continued coverage.