Joe Ligon immediately came to mind after the U.S. Supreme Court ruled Monday that mandatory life sentences for juveniles convicted of murder are unconstitutional, violating the Eighth Amendment prohibition against "cruel and unusual punishments."

Ligon, rotting in Graterford, was convicted at age 15, almost six decades ago.

Labeled "orthogenically backward," he went to a special school and today reads at a third-grade level. As he told me when I visited him two years ago, "I'm one of those slow learners."

Ligon was instructed to plead guilty at a one-day trial that in 1953, I suspect, did not offer adequate representation to a poor, "orthogenically backward" black teenager. The five other defendants have since been released or died.

The United States leads the world in incarcerating juveniles for life in prison without possibility of parole. Pennsylvania leads the nation by far, with almost a quarter of them. Of Pennsylvania's prisoners, more than 60 percent are from Philadelphia.

Really, making the Human Rights Watch list is no reason to crow.

"Mandatory life without parole for a juvenile precludes consideration of his chronological age and its hallmark features - among them, immaturity, impetuosity, and failure to appreciate risks and consequences," Justice Elena Kagan wrote for the 5-4 majority, an argument legal and academic experts have been making for 16 years.

"Adolescents are not adults," says Temple's Laurence Steinberg, an authority on juvenile behavior. "We can't predict how someone acts at age 14 is how he's going to act at age 24." Although "80 percent of all male teenagers in the United States have done something against the law that could get them arrested," he says, "90 percent of juvenile offenders do not become chronic adult criminals."

Teenagers are more capable of change and rehabilitation. They age out of behavior Steinberg characterizes as "more impulsive, more shortsighted, more easily influenced by peers." As Ligon told me, "For 40 years I've had no citations for misconduct."

If the purpose of prison is rehabilitation, can't this be achieved in six decades? Where is the quality of mercy? It has cost approximately $2 million to warehouse Ligon when he's most likely been a danger to no one. He's an old man, his hair a tuft of cotton, with "six teeth left in my head."

Some offenders will never get out and shouldn't. But because of the Supreme Court's ruling, each of those 480 Pennsylvania inmates will have the chance to be heard by the parole board. The fate of being warehoused from adolescence to death, without any chance of freedom, will become rare. Such punishment will be up to the judge's discretion based on the evidence in the case, not mandated by state law.

"This is a sweet victory, really gratifying," says the Juvenile Law Center's Marsha Levick. "The court is still moving forward in the right direction where a majority has consistently hewed to this line that kids are different. Youth status is very relevant under the Constitution."

Public defender Bradley Bridge has handled the Philadelphia cases since 2005.

"We just want the opportunity to show that these people have demonstrated sufficient rehabilitation to merit parole," Bridge says. "I would be hopeful the state parole board would hear some of these cases within the year."

Foremost among them is that of Joe Ligon.

"To someone who has been in prison for six decades and is now 75 years old," Bridge says, "one more year is not speedy enough."

Every few months, Ligon sends me a letter asking for help. Steinberg, Levick, and Bridge get stacks of inquiries from prisoners, pleading for freedom.

"I've got letters from inmates who have been in prison for a very long time who did something very bad when they were teenagers," Steinberg says. "The inmates don't say they're innocent. They say, 'Hey, I was stupid when I was 14. Now I'm 40, and I'm not stupid anymore.' "

And for years there was nothing anyone could do to alter their situations. Monday that all changed.

"The world ain't the same. I seen that on TV. I heard that on the radio," Ligon told me. "I hope I live long enough to see the world change. One of my main concerns is that no one be ever again treated the way I was treated."

Ligon has lived long enough, almost all behind bars, to see that no one will.