There may be no worse place to live in New York City than on Rikers Island, and it is an even worse place to die—locked inside of a jail, forcibly separated from family and friends. Most people whose lives end on Rikers die of natural causes, but there is no doubt that some deaths there have been caused by the culture and conditions of Rikers itself. This tally of preventable deaths includes: Jason Echevarria, twenty-five, who swallowed a packet of soap in his cell, screamed in agony for hours, and died after guards refused to take him to the medical clinic; Carlos Mercado, forty-five, a diabetic in desperate need of insulin, who collapsed in a hallway his first day in jail; Ronald Spear, fifty-two, a kidney-dialysis patient, who died after being kicked in the head by a guard.

Every year, several thousand people across the country die while imprisoned. Local officials report the number of deaths to the Department of Justice, but very little attention is paid to the question of how many of these deaths could have been prevented. Several years ago, Homer Venters, a physician and the former chief medical officer for New York City’s Correctional Health Services, sought to answer this question. Between 2010 and 2016, there were a hundred and twelve deaths in New York City jails. Venters and his team found that ten to twenty per cent of those deaths each year were “caused by actions taken inside the walls” of a jail. He calls these “jail-attributable deaths,” and writes that some years the percentage of such deaths “rose to half or more.”

Reporters have virtually no access to the jails on Rikers Island, but, for many years, Venters had a rare vantage point from which to observe its inner workings. He started working on Rikers in 2008, overseeing health care for thousands of people imprisoned there. On an island known for abuse and violence, Venters became a legendary figure; he often spoke about human rights and was known for his persistent advocacy on behalf of inmates. He left the city’s jail-health service in 2017, and now he has written a crucially important book, “Life and Death in Rikers Island,” in which he examines one of the most overlooked aspects of mass incarceration: the health risks of being locked up.

Eight jails now operate on Rikers, each with its own medical clinics, where incarcerated people go if they feel sick or need follow-up care, often for diseases like diabetes or asthma. But part of what makes jails such health risks for the people confined there is the insidious way that the environment undermines the ability of medical staff to perform their jobs. In 2013, officials at Rikers stopped allowing incarcerated people to walk to clinics alone; now a guard had to escort them—and, suddenly, inmates were missing their appointments nearly half the time. Venters writes, “We would give security staff list after list of the ‘must see’ patients whom we feared might die without receiving care.” This strategy worked, but only temporarily. “We might make a brief improvement,” he writes, “and then a friendly deputy warden would be promoted, transferred, or fired, and we would fall back to half or fewer of our patients being produced.” Although the situation has improved, the problem persists.

The culture clash between guards and medical staff on Rikers was apparent even in the way that the two groups spoke about the people confined there: guards called them “inmates,” while medical workers called them “patients.” At times, medical staff found themselves caught in an ethical dilemma: Was their primary loyalty to their patients or to the system in which they work? This conundrum is known as “dual loyalty,” and Venters writes that, on Rikers, the “most dramatic and tortured aspect of dual loyalty” involves the role that medical staff play in sending people to solitary confinement. Jail managers who wanted to lock an individual in solitary first had to obtain “clearance” from a mental-health worker—assurance that the inmate would not harm himself if isolated for twenty-three hours a day. Venters is a fierce critic of the process. “Health clearance for solitary is not based on any reliable science and violates basic medical ethics because, of course, that patient is supposed to suffer,” he writes. “It’s punishment, after all.”

Rikers has long been notorious for its culture of brutality, and, soon after Venters started working there, he sought to determine exactly why so many inmates were being injured. The main cause of injuries was fights with other incarcerated people, but the secondary cause—accounting for about a quarter of injuries—was listed as “slip and falls,” according to official records. Venters and his team developed an injury-surveillance system, with drop-down menus where medical staff could document how and where the injuries had occurred. Soon a pattern of abuse by guards emerged—and the prevalence of slip and falls made more sense. If an incarcerated person had his nose broken by an officer’s fist, he was unlikely to tell the truth when brought to the medical clinic; fearing retaliation from guards, he might instead say that he had slipped in the shower.

Venters began combing this electronic database each week, identifying patients whose records showed that they had “sustained serious injuries during an interaction with correctional officers,” or whose stories of how they got hurt did not match their injuries (“like a jaw fracture from falling on a toilet”). “Then, at about 5:00 pm on Fridays, I would take my list and go to the jails where these patients were being held,” he writes. At that hour, he knew that he’d be able to move around with more freedom and less scrutiny, and he always made a point of wearing his stethoscope. But, he writes, “Within a few weeks of starting these Friday night encounters, the inmates and DOC [Department of Correction] staff alike came to recognize that I was coming to these housing areas and intake pens for reasons that went beyond simple checkups.” He continues, “Correctional officers would stiffen and slow-walk my requests to see patients. In some instances, officers would outright refuse to produce patients for me to see.”

Sometimes, Venters would encounter a patient whose injuries were more serious than the medical staff had initially thought, and he would try to correct the record. But when he would send an e-mail to D.O.C. officials asking to upgrade an injury, he recalls that he would get back “a flood of responses” intended to derail his efforts. Venters recounts one visit from a D.O.C. investigator “with zero clinical training” who “tried to poke holes” in his diagnosis. “Her challenging of my clinical assessment that a patient had suffered a nasal fracture was maddening,” he writes. “But had I been one of our hundreds of physician assistants or physicians”—instead of a senior official—“the message would have been clear: this isn’t a path you want to go down.”

To conceal the extent of the abuse toward inmates, Venters discovered, guards would sometimes hide individuals with suspicious injuries in remote jail cells. Venters describes receiving a call one day from a doctor who reported that guards had just beaten a patient in a waiting area at a clinic and that “the patient had been dragged away without receiving care and had not been seen since.” Venters went searching for him. “After failing to find him in any of the normal hiding spots in this jail, I went to another facility where ‘problematic’ patients were often sent,” he writes. “I found him in a remote part . . . and heard him sobbing before I saw him in his cell.”