People line up for entry into the U.S. Supreme Court where justices are debating whether executions of teenage killers are unconstitutionally cruel, October 13, 2004. Currently, nineteen states allow the death penalty for 16 and 17-year-olds, and some 70 juvenile murderers are on death row.

© 2004 Reuters

Ten years ago this month, the United States Supreme Court found the death penalty unconstitutional when imposed on people who committed crimes when they were younger than age 18.

The decision, Roper v. Simmons, spared the lives of 72 inmates on death row at the time. It also paved the way for later decisions that addressed other abusive sentences.

Until that moment, the US had been the world leader in executing juvenile offenders. In fact, just eight other countries had put juvenile offenders to death between 1990 and 2004, and the 19 executions of juvenile offenders carried out in the US during that period equalled the known total for the rest of the world combined.

The court had considered the constitutionality of the juvenile death penalty before, but in 1989 ultimately decided that the punishment was acceptable for someone who was 16 or older at the time of the crime.

So what had changed in a decade-and-a-half?

Advances in neuroscience, for one thing. Research was beginning to show what we already knew from everyday experience: teenagers have limited comprehension of risk and consequences, and they are much more likely than adults to engage in risky behavior, particularly with peers.

These studies confirmed that for most adolescents, risk-taking and criminal behavior is fleeting. That means that young offenders are particularly amenable to change and rehabilitation.

International law also played a part. The court in Roper cited the Convention on the Rights of the Child and other human rights treaties and incorporated points made in the amicus brief submitted by human rights organizations, including Human Rights Watch.

The Supreme Court has since gone on to apply these lines of reasoning to juvenile offenders sentenced to life without the possibility of parole – incrementally, to be sure. In Graham v. Florida, the court struck down life-without-parole sentences for juveniles convicted of crimes other than homicide. In Miller v. Alabama, the court determined that the mandatory imposition of life-without-parole sentences for juveniles, including those convicted of homicide, violates the US Constitution.

The Supreme Court hasn’t yet addressed the non-mandatory imposition of life without parole for juvenile offenders. It’s also left open the question of whether resentencing was available to people already serving mandatory life-without-parole sentences for crimes committed when they were juveniles – although a case now before the court could resolve that question and apply the rule of Miller retroactively, as Florida’s highest court has just done.

Now that the US is out of the business of executing juvenile offenders, the shameful club of countries that put children to death has only a handful of members. Pakistan and possibly Iran have carried out such executions this year; Yemen also likely has juvenile offenders on death row.

US juvenile justice practices still don’t fully comply with international standards, but Roper and the cases that followed represent enormous strides forward. Roper also removes any cover for the few other countries that continue to engage in the abhorrent practice of putting people to death for crimes they committed as children.