An Idaho teen has been sentenced to spend the next 20 years in an adult prison, forcing correction officials to look across the country to find a safe place for the 16-year-old to do his time.

Eldon Samuel III was just 14 when he shot to death his drug-addicted father and then shot, stabbed and hacked to death his autistic younger brother in their northern Idaho home.

Last week, 1st District Judge Benjamin Simpson sentenced him to spend the next two decades in prison, starting immediately. But federal laws prohibit minors from being held within sight or sound of adult prison inmates.

Currently, the only way for Idaho prisons to meet those standards is to place the teen in solitary confinement.

That's got Idaho Department of Correction officials scrambling to find a solution.

"We need to keep him separate from our adult offenders, and unfortunately there are no other juveniles in our system," said Ashley Dowell, the department's deputy chief of prisons.

The solution will likely be an out-of-state prison, Dowell said. Minors aren't unheard of in Idaho prisons, but haven't been a significant portion of the state's prison population for decades.

Today, there is just one other minor under IDOC jurisdiction — a 17-year-old girl who is on probation. Another juvenile is serving a blended sentence and is expected to be transferred to an adult facility at age 18.

Samuel has already done time in solitary. He spent more than three months in a 9-foot by 12-foot holding cell in a Kootenai County Jail when he was first charged.

Experts believe extended solitary confinement amounts to cruel and unusual punishment, and the American Civil Liberties Union of Idaho intervened on Samuel's behalf, asking the court to move him to juvenile detention.

Eventually, a judge agreed and sent Samuel to a local detention facility until his trial was complete.

The teen is returning to solitary for at least the next several days, however, as he undergoes the same receiving and diagnostic process that all state prison inmates go through.

ACLU-Idaho spokesman Leo Morales said his organization is watching Samuel's case closely.

"What this raises again is a serious issue with regards to our prisons in this state, an issue with how our judges sentence juveniles. We know that solitary confinement is really cruel and unusual, particularly for juveniles," Morales said.

IDOC research analyst Sean Falconer said in an email that the vast majority of people who came under IDOC custody as juveniles were sentenced to either probation or a so-called rider program, where they serve a few months in prison before they are evaluated for possible early probation.

Falconer said there are currently 218 adults who came under IDOC jurisdiction as juveniles, including 86 inmates currently serving prison terms.

Juveniles are also a rarity in adult prisons nationwide.

The U.S. Department of Justice's Bureau of Justice Statistics estimates that there are roughly 1,200 youths held in adult state prison facilities, according to a 2013 report. That's less than a tenth of a percent of all inmates.

And that number has been dropped dramatically over the past several years: Nearly 4,000 juveniles were held in state prisons in 2000.

Florida, New York, Georgia, Connecticut and Michigan currently have the highest numbers, according to the BJS report.

In Idaho, juveniles charged with certain felonies are automatically tried as adults. But those that are sentenced are often given blended sentences, serving time in a juvenile detention center until they become of age and can be transferred to an adult prison.

During Samuel's sentencing hearing, Kootenai County Public Defender John Adams urged the judge to allow the teen to stay in juvenile detention for now, moving him to a prison when he turns 19 or 21.

Adams cited Samuel's traumatized upbringing: His father was abusive, both children were neglected and Samuel was in charge of caring for his autistic brother. His father also believed that a zombie apocalypse was imminent, and tried to train Samuel to fight off the monsters in case of a doomsday event, according to court testimony.

However, the judge noted the seriousness of the crime. Samuel's younger brother tried to hide under a bed, but Samuel found him and shot, stabbed and hacked the child with a machete more than 100 times.

The judge said he wasn't comfortable having the teen housed with other juvenile offenders, opting instead to house him in adult prison for the entirety of his sentence.