- Today, the criminal justice system is in the midst of a painful reckoning as states determine whether the life sentences of more than 2,000 people should be reconsidered.

That's because they were given mandatory life terms as juveniles, which the Supreme Court has since ruled unconstitutional.

So how did so many kids get life behind bars in the first place?

- It was a trend that took off in the '80s and '90s, when fear of teenage crime was at a fever pitch.

Criminologists were warning about a supposed new breed of remorseless teen killers, so-called superpredators.

(ominous music) Along this stretch of grassy road, one night in early September 1994, when most grade schoolers were getting ready for a new school year, a grizzly murder took place.

- [Anchor] In Chicago, the body of an 11-year-old gang member nicknamed Yummy is found beneath an underpass.

- [Reporter] Police say Robert was murdered by two members of his own gang, 16-year-old Craig Hardaway and his younger brother.

- [Masud] Derrick Hardaway was 14 when he and his brother drove to the underpass to kill Robert Sandifer, or Yummy.

Sandifer himself had shot and killed a teenage girl before he was murdered.

Derrick waited in the car while Craig pulled the trigger.

- I remember the night but things took place.

He got a page from a guy named Kenny.

I'm not actually sure what he said to my brother, but it was to kill Robert.

- [Masud] Derrick and his older brother belonged to Chicago's Black Disciples gang.

- If I was told to do certain things, even I didn't want to do it, it was either do what I'm being told or have it done to me.

- [Masud] Robert Sandifer's murder was big news.

The story scared people, says criminologist Barry Krisberg.

- This was no longer a Chicago story.

This was a story that no matter where you lived, you turned on the evening news and you would hear about this case.

- [Clinton] By now, nearly all of us know the story of Robert Sandifer.

- There was a sense that the country at large was going to hell in a hand basket.

No one had a clear idea of what to do.

- [Masud] Political scientist John Dilulio taught at Princeton and had done extensive research in prisons studying the criminal justice system.

From 1984 to 1994, when Sandifer was killed, teenage homicide rates had more than doubled.

- It seemed like there was a high-profile, major, heinous crime in the news almost every day or every week.

Random, senseless violence.

- Teenage killers, the homicide rate for juveniles now has surpassed the rate for adults in this country.

- [Masud] Dilulio looked at studies that estimated that by 2000 there would be a million more teens between the ages of 14 and 17, and he predicted crime rates would snowball even more.

- You'd have a doubling or a tripling in the rate of youth violence in the time between the mid-'90s and up to through the mid-2000s.

- [Masud] Perhaps most troubling to Dilulio was what he saw as an indication that the small percentage of kids who commit the most violent crimes would be much more destructive than a generation before them.

- Studies found that essentially 6% of every male youth cohort was responsible for about 50% of all the violent crimes committed by that cohort.

That small fraction of people is gonna be able to wreak incredible havoc.

- [Masud] Dilulio wasn't the only one predicting a surge in crime.

- By the year 2005, we may very well have a bloodbath of teenage violence.

- [Masud] Northeastern University criminologist James Fox says his choice of words was deliberate.

- I did sound an alarm, and I did use some rather strong language in terms of what might happen if we didn't react quickly.

- [Masud] Fox and Dilulio felt compelled to call attention to this perceived problem.

Dilulio, an Ivy League academic from South Philadelphia, wrote this article for The Weekly Standard in 1995.

- The term superpredator originated from an inmate who said, as almost a throw away line, he said you know, these kids, they're stone cold predators.

- A superpredator is a young juvenile criminal who is so impulsive, so remorseless, that he can kill, rape, maim, without giving it a second thought.

- [Masud] And like a match to a flame, the word caught on.

- Superpredator.

- Predator.

- Predators.

- Superpredators.

- [Masud] Linguist Ben Zimmer is the language columnist for the Wall Street Journal.

- When you use a word like predator, it is loaded with certain assumptions about the way that an animal hunts another animal.

And so, to call someone a superpredator really amps that up even more.

- We're talking about a group of kids who are growing up essentially fatherless, godless, and jobless.

- [Masud] Dilulio says that he wasn't pointing to any particular racial group as being the most potentially violent.

But in 1996, he wrote that as many as half of these juvenile superpredators could be young black males.

- Race was the central issue.

That as the number of minority children, principally African-American but also Latino children, to the extent that that number was increasing in the society, with them would come a big crime increase.

- What's required in moral panic is the identification of a particular group of people who are demonized in some way.

- When you describe another group as godless, you can do anything to them.

- [Masud] Lawmakers seized the moment to spur on the overhaul of a legal system they considered to lax.

- The kids that once stole hubcaps now rape and murder.

No fear of punishment.

Experts call them superpredators.

- They are not just gangs of kids any more, they are often the kinds of kids that are called superpredators, no conscience, no empathy.

- There are no violent offenses that are juvenile.

You rape somebody, you're an adult.

You shoot somebody, you're an adult.

- Virtually every state, almost 45 states, enacted laws cracking down on juvenile offenders, making it easier to prosecute youth in adult criminal courts, increase penalties.

- [Masud] But at the same time the laws were being enacted, juvenile crime rates were already starting to show a surprising trend.

- Juvenile crime rates have been plummeting during this period of time, in the wake of this panic.

- [Masud] The drop in juvenile crime has been attributed to many things: A stronger economy, better policing, a decline in crack cocaine use.

But Dilulio's research had not foreseen any of these trends.

- We were on the precipice of being able to explain and predict all kinds of things, poverty trends, crime trends, and so forth, none of that work, none of those predictions in any of those fields have born fruit.

- [Masud] By the late 1990s, after a steady decline in juvenile crime, Dilulio could see just how mistaken he was.

- And predictions were off by a factor of four.

It had doubled, and it was supposed to double again, and instead it was halved.

And so, that's about as far off as one could possibly get.

The superpredator idea was wrong.

Once it was out there though, it was out there, there was no reeling it in.

- [Masud] The experience was a turning point.

Dilulio would go on to work in the Bush administration as Director of Faith-Based and Community Initiatives.

- I lost faith in social science prediction at about the same time that I gained faith of a traditional religious kind.

I went into religion and public affairs for the same reason I went into crime and corrections policies, that I thought that's where the most important issues and where the most good could be done.

- [Masud] But Krisberg says Dilulio's turnaround came too late to reverse the damage.

- It was a myth, and unfortunately it was a myth that some academics jumped onto.

The fear over the superpredator led to a tremendous number of laws and policies that we're just now recovering from.

- [Masud] In 2012, a case challenging mandatory life-without-parole sentences for juveniles made it to the Supreme Court.

A brief filed in support of the case denounced the superpredator theory.

It was a public repudiation, yet Fox and Dilulio both signed on.

- As I signed the amicus brief, I thought that although the arguments were a bit one-sided, it came to the right conclusion, and so I signed it.

Because at the end of the day, what's gonna matter most?

What did you do and why did you do it, and did it make a positive difference?

- [Masud] The Supreme Court agreed with Dilulio's side.

- Automatic mandatory life sentences, the justices said, amount to cruel and unusual punishment.

- [Masud] The court recently ruled that decision would apply retroactively to more than 2,000 people already serving mandatory life sentences for crimes they committed as juveniles.

- I made a bad choice.

- [Masud] Citing research showing that teenagers' brains aren't fully developed, making them less culpable for their actions.

- The justices wrote that a young person's immaturity reduces their accountability.

Juveniles have an inability to assess consequences, are often rash, and are prone to risk taking, things that should be considered when sentencing.

- [Masud] In 2016, Derrick Hardaway was released on parole after serving nearly 20 years in prison for his role in the death of Robert Sandifer.

- When I got sentenced, being told you got to do more time in prison than you actually lived at that time, that's harsh, especially for a 16-year-old, to accept.

- [Masud] John Dilulio has worked with three White House administrations to try to implement faith-based initiatives in needy communities, but he says he's out of the business of forecasting.

- Demography is not fading, criminology is not pure science and that lesson, I think, this episode from 20 years ago, and I think many, many other things in public policy mean that we should carve that in stone and put it above every research institution and every foundation.