According to a report being published today by Amnesty International and Human Rights Watch, the United States is the only country to punish juveniles so severely on a routine basis. They counted 2,225 child offenders locked up for life across 42 American states. In the rest of the world, they found only a dozen other cases, restricted to three countries - Israel, South Africa and Tanzania.

"Criminal punishment in the United States can serve four goals: rehabilitation, retribution, deterrence and incapacitation," the report concludes, and that no punishment "should be more severe than necessary to achieve these stated goals. Sentencing children to life without parole fails to measure up on all counts."

Some American states permit the imposition of a life sentence without parole to offenders as young as 10. The youngest actually serving such a sentence are 13. Roughly one-sixth of those locked up for life committed their offences when they were under 16. Almost 60 per cent were given their life sentence for their first offence.

In most cases, the crime in question was murder. But about a quarter of those locked up, the report found, were not the actual murderers, merely participants in a robbery or burglary in which a murder was committed by someone else. In many American states, draconian laws stipulate that being present at the scene of a murder can be equivalent to being guilty of the murder, with punishment meted out accordingly.

The report found that while the number of juvenile offenders being sentenced to life had gone up markedly over the past 25 years, the rate of serious juvenile crime had gone down. In most years since 1985, juvenile offenders have been sentenced to life without parole at a faster rate than adult murderers.

The imposition of severe sentences on juvenile offenders has coincided with a general crackdown on crime in the United States over the past generation. Politicians have found that it pays electoral dividends to advocate an attitude of "lock 'em up and throw away the key".

As a result, state and federal legislators have introduced ever tougher regimes of mandatory minimum sentencing, including one notorious law in California whereby even non-violent offenders can face life without parole if they are caught three times. One of the mantras often heard in political circles is that offenders should do "adult time for adult crimes".

Amnesty and Human Rights Watch said it was inappropriate to deny the possibility of rehabilitation to teenagers. Sentencing them to life inside a prison removed motivation to pursue an education or any self-improvement. Being in an adult prison rather than a juvenile facility also exposed them to a heightened risk of assault and rape.

Sentencing children to life without parole is forbidden under the United Nations' Convention on the Rights of the Child, which has been ratified by every member state except the US and Somalia. Out of 154 countries surveyed in the report, 13 were found to have laws on their books permitting life sentences for minors, but nine of these had never actually imposed one.

Peter A, 29, lifer: A sentence disowned by the judge forced to deliver it

Peter A, a black child from a broken home in Chicago, was just 15 when he went on a crime spree, ostensibly to recover some stolen money and drugs stolen from his older brother. The outing resulted in the shooting of two men, but Peter neither participated in nor witnessed the killings.

In fact, he later testified, one of the murder victims was a friend of his who had nothing to do with the original theft. While the shootings took place, Peter was sitting in a van parked in the street. He was charged with "felony murder" anyway because he had accompanied the two killers and, by his own admission, stolen the van in which they travelled to the house where the murders took place.

The trial judge, Dennis Dernback, sympathised with Peter, calling him a "bright lad" with rehabilitative potential and accepting that, in the absence of his father, he had fallen under the bad influence of his older brother. Judge Dernback's hands were tied, however, by Illinois' sentencing code.

In his written sentence condemning Peter to life imprisonment without parole, he stated: "That is the sentence that I am mandated by law to impose. If I had my discretion, I would impose another sentence, but that is mandated by law."

Peter (not his real name) is now 29. He has obtained a high-school equivalence diploma and completed a course in legal studies. He works in the prison library. The only strike against his disciplinary record has been a single bad report - for the offence of possessing an extra pillow and stashing extra cereal in his cell.