Their text messages were meant only for each other. But now hundreds of one young couple's intimate written exchanges have been exposed as the dramatic focus of a trial that could land a woman in jail years after her boyfriend killed himself.
The blockbuster case playing out this week in a Massachusetts courtroom lays bare the special challenges that text messaging -- unlike a phone or face-to-face conversation -- poses for teenagers, nearly 60% of whom cite texting as their primary form of smartphone communication, experts say.
"Messages that are delivered electronically are very powerful," said Barbara Greenberg, a teen, adolescent and child psychologist. "Kids aren't aware of how powerful their messages are and how their messages might impact others."
Key issues that trip up texting teens include expecting their messages not to be seen by other friends, parents and potentially the police; misinterpreting the tone of messages; and navigating peer pressure and other coming-of-age hurdles, experts told CNN.
While the obstacles crop up in small ways every day, they've also been revealed in other tragic cases that centered on young people's virtual chatter. Text messages among high school friends detailing a night of heavy drinking and sexual abuse played a critical role in rape convictions in 2013 in Steubenville, Ohio. And an alleged prank send via text message apparently led to the suicide this year in Michigan of an 11-year-old boy.
Prosecutors in Massachusetts have described a torrent of text messages that defendant Michelle Carter sent to her boyfriend, Conrad Roy III, encouraging him to take his life. Roy, then 18, died after inhaling carbon monoxide as he sat in his pickup truck. Carter, now 20, is being tried in juvenile court because of her age at the time of the alleged crime.
Not necessarily a safe space
Some teenagers view texting as a "safer" way to talk about sensitive topics, said Michele Ybarra, president and research director at the Center for Innovative Public Health Research and an adjunct professor at Johns Hopkins University.
"You can sort of broach the topic, and it doesn't have to be this huge thing," Ybarra told CNN. "And you can send it to the other person when they aren't necessarily in the same room."
Teenagers also view texting as more private than it actually may be, Ybarra and her research colleagues have found.
In one study, teenagers were paired up and told that Ybarra and her team would monitor their text exchanges. While some pairs seemed cognizant of the wider audience peering in on their conversations, other pairs eventually delved into very personal topics.
"There's an assumed intimacy when you communicate to someone on a one-to-one level, and technology doesn't reduce that," Ybarra said.
Carter's communications with Roy on the day he died also included a 46-minute phone call, prosecutors said. While Ybarra cautioned that this phone call could have played a major role in Roy's decision to take his life, she said she also would not be surprised if its content mirrored the couple's text messages.
Themes often cross modes of communication, Ybarra said.
"What's unique is that the digital footprint of texting remains," she added, noting that "when you consider cases like this or other cases where harm has come to one person, the digital footprint that texts leave has become an incredibly useful tool for police and prosecutors."
Developmentally, teenagers struggle with identity, impulse control, and considering the consequences of their actions, both experts said. Those issues can muddy the waters of communication in any medium.
"That's a recipe for vulnerability and peer pressure," said Greenberg, who practices in New York and Connecticut.
Difficulty in controlling urges makes it more likely teens will cave to an impulse that studies say affects adults, too: to write and send something on a screen that they'd never say in person, Ybarra said.
"I think it's visual stimuli -- the nonverbal cues (of face-to-face interaction) -- that can be incredibly powerful," she said. "Sometimes people can find that more difficult to tap into when there's a screen."
Another tricky area in text messaging is tone, Greenberg said. Messages intended to be positive often are interpreted as neutral, and neutral texts often are read as negative, she told CNN.
"The tone gets misread (in) the communication between the teenagers," Greenberg said. "They aren't necessarily delivering the type of message they want to deliver."
The quick nature of texting -- which denies teenagers, in particular, time to reflect on the messages they send -- doesn't help matters, she added.
Monitor and talk
While young people face special challenges when communicating by text message, it doesn't mean teens, especially older ones like Carter, should not be held responsible for their actions, Greenberg said.
"Sometimes because we feel like these are teenagers and their brains aren't fully developed, we hold them less accountable than we actually should," she said.
"At 17 years old, a teenager has the agency to know better, has the ability and the brain capacity to know how influential she is," Greenberg said, referring to Carter.
To help teens navigate these situations, parents should monitor their communications at a level that suits their family dynamic, the experts said.
And because themes from in-person conversations can carry over into text messages and social media, parents have a duty to talk with teens about healthy relationships and bullying, Ybarra said.
"The way that we think about text messaging is that it's integrated into our lives," she said, "and the conversations we're having with our teens should be more integrated into their lives."