A federal judge Thursday opened the door to stripping New York City of control over Rikers Island, in a hearing that highlighted the daily chaos that reigns in the jails despite repeated assertions by Mayor Eric Adams and his allies that conditions are improving.

Just two days ago, according to data presented at the hearing, staffers used force against detainees 29 times. There were 12 fights among detainees and 10 incidents in which detainees harmed themselves or said they wished to. There were nine assaults on staff and seven fires. Jail workers recovered cocaine, fentanyl, marijuana, Prozac, Ambien, 15 sharp objects and two iPhones.

To alleviate a crisis in which a normal day can include numbers like those, the judge, Laura Taylor Swain, will now allow federal prosecutors and lawyers for detainees to argue that an outside authority should take over the jails. On Thursday, she set a schedule for a series of legal arguments that may shape the future of the city’s jail system.

Judge Swain, of Federal District Court in Manhattan, said that while she had not given up on the city, it had not shown that it was willing or able to keep people in custody safe.

“The people incarcerated at Rikers are at a grave risk of immediate harm,” she said.

Though Judge Swain’s decision on Thursday is a major step, there is still no guarantee that she will appoint an outside authority, known as a receiver. That decision is months away, and would follow prolonged legal arguments between prosecutors and detainees’ lawyers, who are working together, and the city. The first legal filing on the road to receivership is due in November, and the process is not expected to be completed until next year.

If appointed, the receiver would have powers that correction commissioners do not. Backed by Judge Swain, he or she could override state and local laws, cutting through red tape and employment rules — which could mean severing or limiting the relationship between the jails and the correction officers’ union, which has major sway over how they are run.

Experts have warned that a receiver — who would be chosen by the judge — would still have a difficult time given the depth and complexity of the problems that bedevil Rikers Island.

The jail complex tumbles from crisis to crisis. The most recent began in 2020. With New York still in the throes of the pandemic, hundreds of correction officers began calling in sick or simply failing to show up. Their absence created conditions for more uses of force by guards who remained on duty, more serious violence among detainees and a spike in self-harm. Over 40 people held in the jails have died since the beginning of 2021. Last year’s toll of 19 was the most in nearly a decade.

Mayor Adams and his correction commissioner, Louis A. Molina, insist that the situation is turning around, even as four people died last month.

On Tuesday, one of three recent days of chaos sketched at the hearing, lawmakers toured the jails. Aligned with Mr. Adams against receivership — as well as with the city’s largest correction officers union — many remarked publicly on supposedly improved conditions and posted cheerful pictures of the facilities.

Anna Friedberg, the member of the judge’s monitoring team who rattled off the damning data during the hearing, said the visit was one of several ways in which the administration has sought to shape public perception. She mentioned that the following day, during a tour of the facilities, her team had encountered detainees openly using narcotics.

Immediately after her presentation, Mr. Molina took the lectern and said that the Adams administration has made progress “at a breakneck pace.”

“Things are not getting worse,” he said. “The facts suggest the very opposite.”

His view was disputed. Jeffrey Powell, a federal prosecutor, said that the crisis persists, and that his office “just can’t wait any longer for conditions to substantially improve.” Mary Lynne Werlwas, a Legal Aid Society lawyer for detainees, said that the city in recent months has showed a “disturbingly cavalier attitude toward truthfulness.”

Interviews with those familiar with the system demonstrate that the situation remains dire.

Margaret DaRocha, a trial attorney at New York County Defender Services, said that she had made a special effort to protect one client, whom she declined to name for fear of retaliation from correction officers. Her client is incontinent because he had been shot in the stomach years ago. Ms. DaRocha worried that at Rikers, he would be vulnerable to medical complications, as well as attacks from guards and other detainees.

After communicating her concerns, she learned that the Department of Correction had not moved her client to protective housing. Toward the end of June, he was punched in the jaw by another detainee. He had emergency surgery and is now back at Rikers, where he is being told he does not qualify to have his jaw wound cared for.

Thursday’s hearing had been a long time coming. In April 2022, the U.S. attorney in Manhattan, Damian Williams, suggested that the emergency at Rikers might be solved only if an outsider were to step in. But Judge Swain gave the city more time to right the crisis after hearing Mr. Molina argue that “change must come from within.”

Mr. Molina worked with the monitoring team that oversees the jails, led by Steve J. Martin, to make a plan for change.

By November, 18 people had died either in custody or directly upon release, and lawyers for detainees — the Legal Aid Society and the firm Emery Celli Brinckerhoff Abady Ward & Maazel — asked to be permitted to argue for a takeover. Judge Swain denied the request.

This year, there was a shift. Mr. Martin, who had previously praised Mr. Molina, began to criticize him for opacity, even asserting that the city could not be trusted to accurately disclose the number of people who had died on its watch. Mr. Martin’s dissatisfaction appears to have influenced Judge Swain. In a recent hearing and again in recent filings, she has blasted the city for failing to “address the dangerous conditions that perpetually plague the jails.”

Still, Judge Swain said Thursday that a drastic solution might not be necessary. She warned that she still expects the administration to turn things around.

“I will be watching,” she said. “The people of this city will be watching.” She later added, “Watching in justifiable expectation — as well as in hope.”