One morning when he was 16 years old, my cousin walked out of his childhood home with a box cutter and murdered a 9-year-old boy who happened to be passing by on his bike. After turning himself in immediately afterward, he was taken into custody and never returned home.

There were no discernible warning signs. My cousin was kind and got good grades and played varsity soccer. He and the boy had never met. When my mother called to tell me about it, she said he’d had “a break.” And after hours of evaluation and examination, the only diagnosis he ever got was, in fact, “psychotic break,” which, for the purposes of the law, is equivalent to no diagnosis. No diagnosis meant no meaningful chance for an insanity defense.

At 16, my cousin was convicted as an adult in criminal court, and after years awaiting sentencing at a county jail, given life without parole at a maximum-security prison. On his way to the prison, he told me later, he had a panic attack and blacked out. When it was time to get out of the vehicle, he couldn’t walk. He had to be carried through the gates.

An estimated 1,500 people are serving life sentences without the possibility of parole for crimes they committed as children. Ninety-five thousand others, according to the Equal Justice Initiative, are housed in adult jails and prisons each year. Our separate juvenile justice system exists, in theory, because children — even those who have committed terrible violence — are both more vulnerable than adults and uniquely capable of change. Yet too often, the law decides that a child is no longer a child, and sentences him to an adult facility, sometimes for the rest of his life. And even our juvenile justice system, in many cases and places, has lost touch with its original mission to protect children and foster their rehabilitation.

The legal mechanism that allows a young person to be tried as an adult is called a “transfer.” The underlying rationale is that some children are too bad to be treated like children, or too bad to ever be good again. This rationale facilitates not only transfers but also sentencing. You’ll find its explicit enunciation in each of the Supreme Court’s recent decisions about the fate of children who break the law, a series of cases that, up until this year’s ruling in Jones v. Mississippi, evolved toward leniency: Roper v. Simmons (2005) banned the death penalty for those under 18; Graham v. Florida (2010) banned juvenile life without parole (LWOP) for all nonhomicide crimes; Miller v. Alabama (2012) banned mandatory LWOP for those under 18; Montgomery v. Louisiana (2016) extended Miller retroactively. Though taken together, these decisions formed a wave of momentum toward reform, each decision also preserved a carve out for the child who the Court deemed “irreparably corrupt,” or “permanently incorrigible.” That child who’s too bad to ever be good again.

The Court made clear, in dictums, that such a child is rare. As Justice Anthony M. Kennedy observed in Graham, “incorrigibility is inconsistent with youth.” And some states took these urgings to heart. In the years since Miller, 25 states have banned LWOP for juveniles.

But dictums isn’t binding. Other states paid no heed to the Supreme Court’s urgings of rareness. In Mississippi, eight out of 12 juvenile defendants convicted of murder since Miller have gotten LWOP. In Michigan, following Montgomery’s mandate to offer resentencing hearings to those given LWOP as teenagers, prosecutors denied parole for 60 percent of juvenile lifers. (That includes Evan Miller and Henry Montgomery, who are both still serving their life sentences, despite the landmark cases that bear their names.)

Transfers aren’t rare, either. In Arizona, 82 percent of young people arrested for violent crimes are waived to the adult system. If the question is, when is a child not a child, the answer seems to be, all the time. And especially if the child is Black: Black young people account for 54 percent of transfers nationally, and 70 percent of those sentenced to LWOP since Montgomery. In many states, the exception of the permanently incorrigible young person is far from exceptional.

Leaving aside the factual impossibility of legal “incorrigibility” — how could anyone know such a thing about a young person’s future? — such a notion cuts against the founding mission of the juvenile justice system. In the 19th century, it was a group of women in Chicago who saw the cruelty of a legal system that failed to distinguish between children and adults. After a concerted campaign, these women (many of whom, including Lucy Flower and Julia Lathrop, spent time at Hull House and went on to be pioneers of the Progressive Era) established the first juvenile court in Cook County, Ill. By 1925, there was a juvenile court in every state except for Maine and Wyoming. The purpose of these courts, according to their advocates, was to treat children differently than adults – and to rehabilitate rather than punish.

How far we’ve come from these intentions. Though outcomes are grim for children sentenced to adult jails and prisons — children in adult prisons, for instance, are 36 times more likely to commit suicide than those in juvenile detention centers — even those who remain inside the juvenile system often face conditions that harm rather heal. This month, the Justice Department announced its investigation into five juvenile detention centers in Texas. According to a filed complaint, the reports of abuse included guards impregnating juveniles; guards kicking, body-slamming and choking juveniles to unconsciousness; and an uptick in suicide attempts among juveniles in custody. (Pause here. Replace the word “juvenile” with “child.”)

Though not every facility is as bad as those cited in Texas, some combination of sexual assault, relentless violence, excessive chemical and physical restraints, torture in the form of prolonged isolation and inhumane conditions pervades the juvenile justice system no matter the geography and no matter the form of incarceration. And there are many forms, some bearing perfectly innocuous names: wilderness camps, boot camps, halls, campuses, academies and group homes. Studies have shown that confining children in any setting only increases recidivism and does not make the public any safer.

Of course, there are good actors inside this broken system. Recent reforms, such as rolling back the zero-tolerance policies that have fueled the school-to-prison pipeline, show promise. But at bottom, we have a juvenile justice system whose foundational purpose is to rehabilitate, composed of facilities that make rehabilitation impossible; it also regularly deems children too bad to be rehabilitated, whereby their prospects for a safe life — safe for themselves and others — are all but obliterated. So far, we have not figured out how to lock up a child without perpetuating degradation for the both the imprisoned and the imprisoner, no matter how wholesome the endeavor sounds.

Since my cousin was arrested, I’ve sometimes felt there’s little to be certain of. I have watched him grapple with his crime. I know that he’s unspeakably sorry. In prison, he has worked to build a life — victim awareness classes, church on Sundays, Bible college — and this, to me, looks not at all like “permanent incorrigibility.” Still, I don’t know what should happen to him. Despite my policy opinions, I can’t tell his victim’s family that they’re wrong for wanting him to suffer; I’ve never known their pain.

So in confronting the question of just desserts — what does someone deserve who has taken another life? — I hold onto the words of attorney Bryan Stevenson: “Mercy belongs to the undeserving.” That is mercy’s whole point: No one who needs it deserves it.

And in answer to a related but distinct question — what does a child deserve who has taken another life? — our American exceptionalism speaks volumes: We are the only country in the world that sentences young people to die in adult prisons.

Which is to say, despite all there is to be uncertain of, the way we treat children who break the law reflects a mercilessness at the heart of our carceral crisis, and a sickness at the heart of this country.

Katharine Blake is the author of “The Uninnocent: Notes on Violence and Mercy.” She is a graduate of Stanford Law School and lives in Virginia.