The sort of violence that took the life of a Ukrainian refugee, Iryna Zarutska, on a light-rail train in Charlotte, North Carolina, last month is impossible to make sense of. But that doesn’t mean that murders such as Zarutska’s are unpreventable. Her killing represents a confluence of failures within the structures meant to keep people safe. The country’s criminal-justice and mental-health systems should prevent exactly such incidents. But in recent years, these systems have been weakened, their efficacy deliberately reduced. No society can prevent all murders, but if these systems are restored, the prevalence of similar murders could be greatly diminished.Such an effort begins with understanding more about Zarutska’s alleged killer, Decarlos Brown, and the checks that should have prevented him from perpetrating such violence. Brown was, according to reporting, a frequent offender, with more than a dozen prior arrests. Those include two violent felony convictions, for breaking and entering and armed robbery (the latter while on probation for the former), and two assault arrests, including one for attacking his own sister. In spite of this, Brown was, at the time of the murder, free without bond in an open case stemming from his January arrest for alleged misuse of the 911 system. Much of Brown’s behavior was likely related to his diagnosis of schizophrenia. He was homeless at the time of his arrest; his mother had evicted him because she considered him too violent. Lastly, Brown did not purchase a ticket before boarding the train.Each of these factors—a history of criminal behavior, an open case, a serious mental illness, and a failure to follow the rules of the transit system—was both a red flag and an opportunity for intervention, which could have stopped Brown before he killed Zarutska. Several of those missed opportunities stem from one salient fact: Brown was a frequent offender. Repeat recidivists are responsible for a hugely disproportionate amount of the crimes Americans suffer each year. They are also easily identifiable, thanks to their criminal records. Both the criminal-justice and mental-health systems should be better equipped to root out such criminals, for either treatment or detention, or both. Doing so would yield enormous public-safety benefits.[Charles Fain Lehman: Trump is right that D.C. has a serious crime problem]Let’s begin with a North Carolina judge’s decision earlier this year to release Brown on nothing more than a written promise to return to court in the 911 case. That may have been needlessly lenient, but it’s partly the result of North Carolina law, which determines whether someone is released mostly based on the offense that they are charged with, not their criminal history. In a more sensible system, a defendant such as Brown—with a history of mental-illness-related volatility and serious criminal behavior—should have needed to overcome a presumption that he should be held in jail pending a trial, meaning the burden would be on his lawyer to show why he should not be detained. In North Carolina, defendants charged with serious offenses, such as use of a firearm and certain drug-trafficking crimes, must make such a showing, but those charged with more minor crimes generally don’t have to do so, even if they have an extensive record.A better approach would be for judges to assess the totality of an offender’s risk, including their criminal history. That can be done impartially using algorithmic risk-assessment tools, which use data on similar offenders to translate a defendant’s criminal and mental-health history into a score that gives judges a numerical sense of the person’s risk of flight or reoffense. Such tools have a track record of real-world success, as demonstrated in New Jersey, where the risk-assessment tool actually reduced the pretrial-detention population without increasing crime.These tools don’t always work perfectly—particularly because too many judges disregard their recommendations. But in an ideal world, judges would heed the assessment’s ratings by releasing those who score low and remanding to detention those who score high. Doing so would ensure that demonstrably high-risk offenders are kept off the streets, and low-risk offenders do not have to spend additional time behind bars. Had this been done in Brown’s case, Zarutska might well be alive today.Backing up to before Brown’s arrest for 911 misuse: Why was he free even then? He had a long list of felony convictions, including for armed robbery, larceny, and breaking and entering; he had also avoided federal charges for being a felon in possession of a firearm. At what point is enough really enough? Crime in America, as it is in other nations, is driven by a small population of high-rate offenders who do the large majority of offending. In New York City, for example, the top 10 most frequent offenders have racked up more than 600 arrests; just 63 people account for more than 5,000 subway arrests. Such people are either incapable of playing by society’s rules or are refusing to do so. Unchecked, they make city life worse for the rest of us.[Charles Fain Lehman: New York City has lost control of crime]Curtailing such high-frequency offenders requires meaningful—and mandatory—sentencing enhancements based on their criminal history. Such a system would have offenders accrue points with each felony conviction. Reach a predetermined threshold—à la “three strikes”—and, depending on the nature of the charge that put him or her over, an offender would face a sentencing enhancement that could range anywhere from 10 years to life. The exact threshold would be up to a state’s legislature, but the basic principle is that people with long criminal histories should be taken out of free society for longer than those without.Such laws are often a source of controversy, shocking the public with high-profile failures (people committed to life in prison for minor third offenses) and raising concerns that the laws contribute to overincarceration. Smartly designed habitual-offender laws can address some of these challenges by making sure that only felonies, not misdemeanors, count toward “strikes” and by deducting points from an offender’s total for each year they desist.North Carolina does have a “habitual felon” law, implemented in the 1960s. But the law gives prosecutors discretion as to its use, instead of making the enhancement mandatory. The fact that the state’s law failed, for whatever reason, to sweep up Brown suggests that it may need improvement. Many other states have no such provision, leaving them less able to sort out the high-frequency recidivists among their population.Another aspect that necessitates examination is Brown’s history of severe mental illness. Schizophrenia significantly increases one’s risk of being both a victim and perpetrator of violence, according to a 2022 systematic review. Many people may believe that Brown’s mental illness means his case should be addressed as a mental-health crisis, not primarily by the criminal-justice system. Whether or not that is right, North Carolina’s mental-health-care system clearly failed to keep him psychologically stable enough to avoid him posing a risk to himself or others, including by not confining him to a facility.One major factor in that failure is that North Carolina has grossly insufficient treatment capacity. According to the Treatment Advocacy Center, a nonprofit that supports assertive treatment for people diagnosed with serious mental illness, as of mid-2023, the state had just 453 fully staffed hospital beds for adults with serious mental illness—a 72 percent decline since 2007. People in jail must wait for one of the state’s 82 “forensic” beds (specifically for people with mental illness in the criminal-justice system); the average waiting time is five months. North Carolina’s bed shortage is particularly severe, but almost every state has some degree of a shortage, thanks largely to an obscure provision of the original 1965 law authorizing Medicaid that makes it nearly impossible for federal dollars to cover such care. Some states have responded by shifting patients to facilities that Medicaid will reimburse for treatments while allowing their psychiatric-hospital infrastructure to steadily decline.[Keith Humphreys: America’s incarceration rate is about to fall off a cliff]North Carolina also has struggled with compelled outpatient commitment (sometimes called “assisted outpatient treatment”). Research from the state shows that “seriously violent” patients in AOT were significantly less likely to commit violent acts than people the study identified as “seriously violent” who were not enrolled. The Treatment Advocacy Center has criticized the state for its underuse of AOT in past years. AOT is infrequently used in part because when its patients refuse to comply with their treatment plan but do not meet the standard for involuntary commitment, the state has little recourse. State law currently prohibits forcibly medicating or treating people in AOT. The Treatment Advocacy Center also notes that family members currently have no pathway for petitioning to have their loved one placed in AOT—an intervention that might have helped both Brown and his mother.Finally, consider where Brown’s offense took place, on Charlotte’s Lynx Blue Line. Charlotte’s public-transit system has a reputation for danger. In recent polling, just 37 percent of residents of the surrounding Mecklenburg County described the system’s buses and trains as safe from crime, and just 29 percent called the stations safe. That’s consistent with research showing that extending the Blue Line caused an increase in crime in the immediate vicinity of new stations. But the problem isn’t just in Charlotte. Although major crimes are declining nationwide, crimes on transit remained elevated through the end of 2024, according to data from the Bureau of Transportation Statistics.How can Charlotte keep people such as Brown off the train? The answer goes back to his first offense of that evening—failure to pay his fare. People likely to commit major offenses underground also tend to commit minor offenses: fare evasion, riding bicycles or scooters in a station, or using drugs. In recent years, many jurisdictions have ratcheted back enforcement of these offenses on public transit. Charlotte is only now saying that it will add fare-inspection capacity, following years in which nobody checked tickets.Although violent crime has been receding from recent highs, the murder in Charlotte shows how much work is left to be done. Policy makers should not downplay or disregard the cascading failures evident before Brown boarded that train. Rather, they should look for opportunities to fix the systems that so obviously failed, in ways that make them better for all Americans.