When 15-year-old Luis Cruz joined the Latin Kings in 1991, he was a child by almost any measure: he couldn’t legally drive, drop out of school, or buy a beer. But was he still a child a few years later when—just months after he turned 18—he murdered two people on the orders of gang leaders?
Earlier this year, a federal judge in Connecticut said yes. The judge decided that a 2012 Supreme Court ruling that forbade mandatory sentences of life without parole for juveniles should apply to 18-year-olds like Cruz, and granted his request to be re-sentenced. It’s one of a small but growing number of cases in which courts are grappling with what to do with young adults who commit the most serious crimes.
The years between 18 and 21 are a sort of societal limbo period when, in most states, you can smoke but not drink; make medical decisions for yourself but stay on your parents’ health insurance policy; and try on a variety of identities and life experiences without anyone looking askance.
With this in mind, Connecticut last year opened a dedicated prison unit for young adults aged 18 to 25, and Vermont this year began allowing young adults up to age 21 to have all but the most serious cases tried in juvenile court.
When it comes to the most extreme punishments, the Supreme Court has ruled so far that 18 is a “bright line.” If you’re under 18 at the time of your crime, you can’t be executed. You also can’t be sentenced to life without parole without a hearing to consider your maturity level. But the high court has never extended those protections past age 18.
“The qualities that distinguish juveniles from adults do not disappear when an individual turns 18,” Justice Anthony Kennedy wrote in Roper v. Simmons, the first of four modern cases in which the court has laid out its thinking on these issues. “However, a line must be drawn.”
The high court has not revisited that line since Roper was decided in 2005. But state and lower federal courts have begun to consider whether people between the ages of 18 and 21—the period psychologists now call “late adolescence”—should have the same kind of special consideration that younger teenagers get before they face sentencing for murder.
The Roper case was decided at a time when researchers had recently begun imaging adolescents’ brains. Using functional magnetic resonance imaging, or fMRI—like the technology doctors use to look inside the brain for tumors or strokes—researchers were able to observe how young people’s brains responded to various situations.
Paired with research on kids’ choices and behaviors, the brain scans provided a scientific basis for what “any parent knows,” as Kennedy wrote: juveniles are more immature than adults, more susceptible to peer pressure, and less able to understand the consequences of their actions. That makes them less culpable for their crimes and more amenable to rehabilitation.
But it wasn’t until recently that scientists began to research what happens to the brain in late adolescence and young adulthood, says Laurence Steinberg, a leading researcher into adolescent development who helped write the American Psychological Association’s briefs before the Supreme Court and who has testified in many of the more recent lower court cases.
And when they did, they found that those same youthful qualities seem to persist until the early to mid-20s. In one recent study, Steinberg and his colleagues gave a series of tests to more than 5,000 children and young adults across 11 countries. They found that the impulse to chase thrills and look for immediate gratification peaks around age 19 and declines into the 20s. Steinberg describes this system of the brain like the gas pedal in a car. The “brake” system—the ability to plan ahead and consider consequences—takes longer to catch up: it isn’t generally fully mature until the 20s.
Steinberg says if he had to draw a new bright line, he would draw it at 21.
“Knowing what we know now, one could’ve made the very same arguments about 18-, 19- and 20-year-olds that were made about 16- and 17-year-olds in Roper,” he testified in a recent Kentucky case.
In that Kentucky case, a judge found the state’s death penalty statute unconstitutional because it allows people who were under 21 at the time of their crime to be executed. “If the science in 2005 mandated the ruling in Roper, the science in 2017 mandates this ruling,” he wrote.
A Pennsylvania court last year considered an appeal from a woman who was sentenced to mandatory life without parole after serving as a lookout, at 18, during a botched robbery that ended in murder. The court rejected the appeal on technical grounds, but called 18 an “arbitrary legal age of maturity” and said an “honest reading” of the Supreme Court’s ruling would require courts to reconsider it.
In the last several years, Illinois appeals courts held that an 18-year-old and a 19-year-old could not be sentenced to mandatory life without parole.
Other courts have not been persuaded.
Judges in New York, Ohio and Arizona have rejected the argument, saying simply that the Supreme Court’s cutoff was unambiguous.
The Ohio defendant, who was sentenced to death when, at age 19, he raped and beat to death his girlfriend’s 3-year-old daughter, was executed in 2017.
The defendants in New York, sentenced to mandatory life without parole for a series of gang-related murders they committed between the ages of 18 and 22, have appealed, and a federal court will hear arguments in their case sometime in the next few months. In Connecticut, the judge in Cruz’s case has put his re-sentencing on hold awaiting the judges’ decision in New York.
This month, a Florida judge reluctantly denied a re-sentencing hearing to Quintin Vicks, who was sentenced to mandatory life without parole for his role, at age 18 years and 11 weeks, in an armed robbery that resulted in a man’s death. “The Court disagrees with the result but feels bound to render it,” the judge said, saying it wouldn’t be right to make a decision “based on how the Court thinks the United States Supreme Court will one day rule.”
Justice Kennedy, who was often the Supreme Court’s swing vote in close cases and who voted in favor of all four of the court’s major rulings extending these protections to juveniles under 18, retired this summer. The court is widely expected to tack right when President Donald Trump’s pick assumes Kennedy’s seat. In light of that, opponents of juvenile life without parole are aiming to keep these cases in lower courts for now, said Marsha Levick of the Juvenile Law Center, which has submitted briefs in support of many of these defendants. They’re not likely to get a friendly hearing on the question of whether 18-, 19- and 20-year-olds are less culpable than adults from the newly composed high court, Levick said.
In the meantime, Steinberg, the psychologist, says he has been hired by the attorneys for Nikolas Cruz, who faces the death penalty as the accused gunman in February’s Parkland school shooting in Florida. Cruz was 19 when he allegedly killed 17 people at Marjory Stoneman Douglas High School. Steinberg “struggled about this a lot,” he said. But in the end “it’s really hard logically to say, ‘People your age are too immature to be sentenced to death, unless you do something really, really bad.’”
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A version of this article was originally published by the Marshall Project, a nonprofit news organization that covers the US criminal justice system. Sign up for the newsletter, or follow the Marshall Project on Facebook or Twitter.