As more and more minors serve time in adult prisons, a growing number are placed in solitary confinement. Officials say it's to protect the minors from the adult prison population. Some of those who served time in solitary as teens and their advocates say it's a harmful practice and a dark secret of the criminal justice system. Rock Center Special Correspondent Ted Koppel reports.

By Elizabeth Chuck, NBC News, and Deirdre Cohen and Sarah Koch, Rock Center

Courtesy of the Stewart family James Stewart, who was arrested after being charged with vehicular homicide when he was 17, is seen in an undated school photo.

James Stewart, a 17-year-old from Denver who committed suicide while in solitary confinement, had never been to jail before August of 2008. That was when, under the influence of alcohol and marijuana, Stewart had gotten into a head-on car collision, killing a 32-year-old man.

Because of the severity of his crime, Stewart was charged with vehicular homicide – and charged as an adult. His family couldn’t make bail, so Stewart was placed in the Denver County Jail while he awaited his sentence.

There was just one problem: Since he was a minor, Stewart was ordered to be put in protective custody, separate from the adult prisoners— and the best protection the jail had to offer was solitary confinement.

Weeks later, the psychological impact was too much. After a brief reprieve from solitary to be in a shared cell with another juvenile offender, Stewart was sent back to isolation after a minor argument with his cellmate. According to his older sister, Nicole Miera, Stewart took his own life after less than 10 minutes of being back in what inmates called "the hole."

"It was stated that that when he got in there, he was pretty upset," Miera told NBC's Ted Koppel, her eyes filling with tears. "He had taken a sheet and he had wrapped around his neck and just twisted until he couldn't twist anymore."

Stewart was one of many juveniles who are in adult jails and prisons across America. Not all of their stories end as tragically as his, but the increasingly blurry line between juvenile offenders and adult correctional facilities have made many wonder if better solutions are needed for this growing population.

James Stewart was 17 when he committed suicide after being placed in solitary confinement. He is part of a rising tide of juveniles who commit suicide while being locked away in solitary. Rock Center Special Correspondent Ted Koppel reports.

For each of the past five years, roughly 100,000 juveniles have been held in adult jails and prisons, according to data from the Department of Justice.

Defense attorney Bryan Stevenson, executive director of the Montgomery, Ala.-based Equal Justice Initiative, told NBC these youths are getting unfairly harsh treatment for the crimes they commit.

"Ninety-one percent of the children who are serving time in adult jails and prisons are serving time in jails and prisons for crimes that are not murder, crimes that are not sex crimes," he said. "Solitary confinement is pretty horrible for anybody, but it's especially horrible for a child. It is psychological torture."

‘The dark secret of the criminal justice system’

Data on how many of those young people nationwide are held in solitary confinement isn't available, but a report published this past October by Human Rights Watch and The American Civil Liberties Union said the New York City Department of Corrections, for example, reported that in fiscal year 2012, 14 percent of all detained adolescents were held in solitary at least once.

"I spoke to kids. They talked about being in a cell alone, the size of a parking space, the size of an elevator," said Ian Kysel, who authored the HRW/ACLU report. "This is sort of the dark secret of the criminal justice system. ... Jails and prisons don't make available their data on solitary confinement."

At New York City's Riker's Island, the average length of solitary confinement for youths last year was 43 long, 23-hour days, according to Kysel's report.

The catch-22 of being prosecuted as adults but segregated from the adult prison population because they are still minors is literally making young offenders go out of their minds — and many of them have mental health issues before they are put in isolation, according to the HRW/ACLU report.

Stuart Grassian, a Boston-based psychiatrist who is an expert on solitary confinement, cites CIA research done in the 1950s, which found solitary confinement made American prisoners of war in North Korea go psychotic.

"What was produced by that was a person who was so unhinged, he was confused, disoriented, disheveled," he told NBC News, "They wouldn't sometimes know who they were. They couldn't think."

Kysel, the author of the report on adolescents in adult prisons, has called for youth solitary confinement to be banned and for other punishments — such as taking away privileges — to be instituted instead. Grassian agrees that this is necessary.

"You have these kids getting more and more out of control, more and more impulsive, more and more emotionally out of control because they're in solitary. It's very likely that's going to be a permanent impairment in their lives," he said. "Well, guess what? Ninety-five percent of them are gonna get out back into your community. What do you want them to be like when they get out?"

Rock Center's Rima Abdelkader contributed to this report.