Hi Jclarkdawe, oops, sorry, I forgot to mention earlier that my original plan was to set the story approximately around 1965, with the teens around the ages of 17 and 18 years old, the accused 17 years old.
In answer to your comment "Is the kid's attorney dead? Is the judge dead? Is the appeals court dead? This is not legally sufficient to get a convince. Proof must be beyond a reasonable doubt and this doesn't come close. Have an "eye witness" testify.
According to research on the juvenile justice system, before two US Supreme court cases in 1966 and 1967 juveniles were not entitled to key elements of due process such as a right to legal consul, the right to confront or cross exam witnesses, or even notices of the charges against them, as it happened in the '67 Gault case. It wasn't until 1970 Winship case that usually for a conviction in juvenile court, all you needed for a guilty verdict was a "preponderance of the evidence" meaning that the available evidence makes it more likely than not to that the person committed the crime, instead of the prosecutor having to have evidence of "proof beyond a reasonable doubt" in criminal cases involving adults. The original reasoning was that kids and teens under the age of 17/18 (depending on the state) should not be treated as harshly as adults, so their cases would be treated as civil cases, under a more informal relaxed meeting with a judge. The goal was to rehabilitation for children and the belief that a judge would focus on doing whatever was in the best interests of the child. Of course, a judge could also decide to send the offender to a reformatory institution, which in some notorious cases as the ones in Florida or California, were as dangerous adult prisons.
Following the literary advice of "do terrible things to your main character for an interesting story", the legal guardian of the accused decides not to get an attorney for him since he would prefer to get him locked up in order to take control of the family assets (the parents in the story are dead/incapacitated).