Portside

The portrait that emerged from the report on Rikers Island by the United States attorney’s office in Manhattan last week was of a place with almost medieval levels of violence, meted out with startling ferocity by guards and their superiors.

The two-and-a-half-year investigation, which focused on the abuse of teenage inmates by correction staff, was exhaustive in cataloging the brutality. But a critical question that went unaddressed is how conditions were allowed to get to this point.

Rikers has been a place of violent excess for decades. And the growing ranks of inmates with mental illnesses, reaching nearly 40 percent of the jail population today, have added to the challenges for correction officials.

But conditions worsened substantially under the administration of Mayor Michael R. Bloomberg, which reduced jail staff and failed to curb escalating violence by guards, according to former correction officials, inmates’ advocates and others intimately familiar with the jail.

“There was very little interest in expending political capital and financial capital on the jails,” said Martin F. Horn, who was correction commissioner during Mr. Bloomberg’s first two terms.

As mayor, Mr. Bloomberg earned a reputation for being a consummate manager who leveraged his private sector experience to tackle municipal problems. But he never made Rikers a high priority, at a time when conditions were drastically deteriorating, according to people familiar with its problems.

During Mr. Bloomberg’s last term, use of force by officers on inmates jumped by 90 percent, according to Correction Department data. Inmates’ advocates and public officials charged with overseeing the jails said they pleaded for the administration to address the issue.

“We met with the Department of Correction and the Bloomberg administration about the prevalence of violence directed by correctional staff towards prisoners, and they didn’t respond,” said Dr. Robert Cohen, a member of the New York City Board of Correction, a watchdog agency.

Early on, the Bloomberg administration cut more than 3,000 correctional positions. While some of the cuts were attributable to the declining inmate population and the closing of facilities, Mr. Horn said the reductions eventually went too far. When even more were proposed in 2008, he sent a letter to the city’s budget office, warning that further reductions would be “impossible without compromising the safety of everybody in the jail.”

For the remaining officers, mandatory overtime became the norm. Exhausted guards were increasingly prone to lashing out at inmates, officers and oversight officials said. More recently, during Mr. Bloomberg’s third term, the Correction Department greatly reduced the number of officers responsible for escorting mentally ill inmates to therapy, meaning that many were locked in solitary confinement 23 hours a day and rarely got out for services. Resentment and anger among inmates built, according to a senior health department official, leading to more attacks on guards by inmates.

A mental health task force, created by the Bloomberg administration in 2011, produced few results and lacked participation from key city officials, including Raymond W. Kelly, who was the police commissioner.

Stu Loeser, a former press secretary who is again a spokesman for Mr. Bloomberg, challenged claims that as mayor he was indifferent to conditions at Rikers, noting that at City Hall the mayor sat a few feet from Linda I. Gibbs, the deputy mayor who oversaw the Correction Department, and conferred with her “throughout the day, almost every day,”

The current crisis at Rikers stems in part from aggressive efforts to end the chaos and bloodshed that plagued its jails in the 1980s and 1990s. At the time, the average daily population was around 20,000, almost twice its current level. Gangs like the Netas and the Latin Kings battled one another as well as the guards. The chief problem then was inmate violence. Slashings and stabbings were routine. And a thriving trade in drugs and weapons went virtually unchecked by a demoralized staff.

Today, violence is once again surging, but now it is the guards who are perceived to be at the heart of the problem.

Bernard B. Kerik, who helped oversee Rikers from 1995 to 2000, first as the top deputy at the Correction Department and then as commissioner, is credited with bringing inmate violence under control. A beefed-up SWAT team was equipped with clubs, pepper spray and electrified stun shields. A data system similar to the Police Department’s Compstat was created to identify the jails’ trouble spots.

In 1999, there were fewer than 100 stabbings by inmates, compared with 1,100 five years earlier.

But even as conditions improved, advocates warned that allowing guards to rely so heavily on force could get out of hand.

“Whenever you impose a system of restraint on this scale, it can easily be abused,” Jonathan S. Chasan, a lawyer for the Legal Aid Society, said in a 1999 interview with The New York Times.

The frequency of officers’ using force on inmates remained steady during Mr. Kerik’s tenure under Mayor Rudolph W. Giuliani and dipped during Mr. Bloomberg’s first term, reaching its lowest point in 2004, according to department data. But then it spiked.

In 2004, the department documented 961 altercations with inmates involving force. In 2013, with the ranks of inmates with mental illnesses on the upswing, there were 3,285. In the first six months of 2014, use of force was up by a third.

Mr. Horn, the former commissioner, left shortly after the 2008 beating death of an 18-year-old inmate named Christopher Robinson. Mr. Robinson was killed by a gang of teenage inmates who prosecutors said were enlisted by officers to brutalize other inmates. New York eventually paid $2 million to Mr. Robinson’s mother, and two officers went to prison.

Mr. Horn blamed City Hall for being ignorant of the complexities of Rikers.

Mary Lynne Werlwas, a Legal Aid lawyer, agreed.

“Bloomberg did nothing to restrain his out-of-control work force at Rikers,” she said.

Conditions worsened under Dora B. Schriro, who became correction commissioner in 2009 and was widely criticized by uniformed workers for what they perceived as ineffectual leadership.

Though Ms. Schriro promised changes, her reform efforts often fell short. She had talked of reducing solitary confinement, but it expanded during her tenure. A multimillion-dollar centralized intake facility intended to streamline the processing of incoming prisoners was deemed a failure and closed after four months.

A former senior department official, who declined to speak for attribution to avoid retaliation from former colleagues, worked with Ms. Schriro described her as extremely intelligent, but unable to put her vision into effect.

She appointed chiefs who failed to develop a systematic plan for addressing a longstanding culture of violence, and she rarely toured the jails, preferring to meet off-site with senior staff at department headquarters. She almost never addressed the uniformed staff at roll call, one of the few places where commissioners can communicate directly with officers, the official said.

In an email sent by her spokesman, Ms. Schriro, who is now commissioner of the Connecticut Department of Emergency Services and Public Protection, declined to address the rise in violence, but said that while she oversaw Rikers, “there was an appreciable increase in referrals of staff to the inspector general for criminal prosecution for misconduct including excessive force.”

During her five-year tenure, violence by officers increased almost every year, and the number of serious injuries suffered by inmates in altercations with guards jumped.

Howard Wolfson, a former deputy mayor who is now a spokesman for Mr. Bloomberg, defended Ms. Schriro, saying she had made important changes, such as increasing the number of supervisors and bolstering mental health care, taking advantage of additional money allocated by the mayor’s office. As a result, Mr. Wolfson said, “we experienced the start to improvements in 2013.”

Under Ms. Schriro, former and current correction officials said, the influence of the president of the correction officers’ union, Norman Seabrook, grew. Daniel Selling, a former director of mental health care at Rikers, called Mr. Seabrook “much more powerful than any commissioner.”

The union’s clout has made it more difficult to punish uniformed officers. The federal report identified a lack of accountability for guards as a root cause of the violence.

Over the previous two administrations, there have been incremental efforts to improve conditions, some of which succeeded for a time. But these have been achieved mostly through court intervention.

The department has been the subject of six class-action lawsuits in the past three decades, alleging egregious violence by officers. Five of the suits ended with judges issuing court orders aimed at reducing brutality, though mostly for individual facilities like the solitary confinement unit.

One of the more successful suits, according to Mr. Chasan, the Legal Aid lawyer, led to the stationing of federal monitors to oversee the solitary-confinement cellblocks in the late 1990s and early 2000s, including the supervision of staffing decisions. “If someone had a history of violence, they were turned away,” Mr. Chasan said. “The result was a dramatic decrease of abuse.”

The most recent suit, brought by Legal Aid on behalf of 12 inmates who were seriously injured during encounters with guards, has been certified for class action and is currently the subject of settlement negotiations with the city.

Since taking office, Mayor Bill de Blasio has pledged to bring Rikers under control. He appointed Joseph Ponte, who has a reputation as a reformer, as correction commissioner and allocated $26 million in the new budget for more officers and $6 million for mental health programs.

Mr. de Blasio has embraced advocates in a way that his predecessor never did.

Five Mualimm-ak, the director of Incarcerated Nation, a group that helps inmates who have spent time in solitary, said he had met with Mr. de Blasio five times since the mayor took office. He said he also meets with Mr. de Blasio’s staff at least twice a week.

He met with Mr. Bloomberg once.

Pressure from outsiders, including the news media, the city’s Department of Investigation and now federal officials, to enact changes is the strongest it has been in years. After releasing the report last week, prosecutors gave Mr. de Blasio 49 days to submit a plan to reduce brutality or face federal intervention.

Advocates say they are hopeful about the possibility for change, but they question why it has taken so long.

”I’m encouraged, but I think this attention and action was overdue,” said Jonathan S. Abady, a lawyer who has been pressing brutality cases for 12 years. “Unnecessary violence and excessive force have afflicted Rikers Island like a highly resistant disease for decades.”