Of all the issues being considered by the Supreme Court this winter, none is more emotionally charged than life sentences for teenagers. The justices must decide whether sending minors to prison without any possibility of parole is a “cruel and unusual punishment” prohibited by the Eighth Amendment to the Constitution. It is a narrow point of law, but the purpose of America’s penal system is in the dock.

No other country locks up its children like the United States does. An Amnesty International report found just seven prisoners in Israel, four in South Africa and one in Tanzania serving life terms for crimes they committed before they were legally considered to be adults. There are 2225 such inmates in ­American jails – each one a stark reminder that in the desire to be tough on crime, faith in rehabilitation has been lost.

Defenders of the status quo argue that some rapists, murderers and violent criminals commit acts so heinous they deserve to be imprisoned for the rest

of their lives, no matter how young

they are.

The organisations challenging this include the National Association of Social Workers, Mothers Against Murders, the Correctional Chaplains Association, the Juvenile Law Centre and a list of religious groups who believe that however grave the offence, it is inhuman to offer a child no hope of redemption.

The Supreme Court abolished the death penalty for minors with its decision in Roper v. Simmons four years ago. In his majority opinion, Justice Anthony Kennedy wrote that teenagers are less capable of making mature decisions, more likely to act impulsively and more susceptible to peer pressure than adults. He also observed that because their characters are not fully formed, they have more potential to become productive members of society.

The petitioners in Graham v. Florida argue that this reasoning should apply beyond capital crimes, especially where no death was involved. Terrance Graham robbed a woman at gunpoint in her home, a few weeks after ­completing a previous prison stint for armed burglary and assault. He was 17 years old. The judge sentenced him to life without parole.

The other case being considered by the Supreme Court, Sullivan v. Florida, concerns a mentally impaired 13-year-old who raped an elderly woman. As things stand, Joe Sullivan is one of at least 73 prisoners destined to remain behind bars until they die, for crimes that were committed before they turned 15.

The American Psychiatric Association’s legal brief in his favour notes that neuroscience has shown that during puberty, areas of the brain associated with impulse control and risk evaluation are undeveloped. It concludes that “condemning an immature, vulnerable, and not-yet-fully-formed adolescent to die in prison is a constitutionally disproportionate punishment.”

Quantel Lotts was 14 when he stabbed his step-brother Michael Barton to death, in what began as a play fight. The dead boy’s mother has forgiven him, but the state of Missouri allows no such leniency, having sentenced him to life without parole on a charge of premeditated murder. In several states, there is no minimum age limit at which children can be tried as adults.

Because Sara Kruzan’s father was in jail, she was raised by her drug-addicted mother. By her early teens, she had been coerced into working as a prostitute. The abuse continued for three years, until she killed her pimp. She too was sentenced to life in prison with no hope of being set free.

At the Supreme Court hearings, Shannon Goessling spoke for the National Organisation of Victims of Juvenile Lifers. “This system is not set up for rehabilitation,” she told the judges. “It is set up for retribution and consequences.” Jennifer Jenkins, whose sister was murdered by a teenager, said “there are some people who are so fundamentally dangerous that they can’t walk among us.”

Former Republican Senator Alan Simpson, part of a group of former offenders petitioning for Graham and Sullivan, gave an impassioned response. As a young man, he started fires, destroyed property, recklessly fired his gun and hit a policeman. “For God’s sake, give the guy a chance,” he said. “Sort them out case by case. You don’t just salt them away for life.”

Chief Justice John Roberts has suggested that because “death is different” the Roper ruling has no bearing on custodial sentences for minors. In all likelihood, the decision will again come down to Justice Kennedy.

At one point in the hearing, Mr Kennedy wondered: “What is the state’s interest in keeping the defendant in custody for the rest of his life if he has been rehabilitated and is no longer a real danger?” US prisons currently hold 2.3 million people. The larger question is whether a country that incarcerates six times as many of its citizens as the average developed nation has any interest in rehabilitation at all?