DANNEMORA, N.Y. — Inmates who have served time at the Clinton Correctional Facility here tell of being taken aside by a sergeant soon after they arrive and given a warning: Cross the guards, and bad things can happen.

And they do. Inmates describe being ambushed by guards and beaten, taunted with racial slurs, and kept out of sight, in solitary confinement, until the injuries inflicted on them have healed enough to avoid arousing suspicion.

One story in particular has been passed along over the last few years as a kind of parable of brutality and injustice on the cellblocks. Leonard Strickland was a prisoner with schizophrenia who got into an argument with guards, and ended up dead.

In the inmates’ telling, the guards got away with murder, ganging up on Mr. Strickland and beating him so viciously that he could barely move. The guards deny this, saying they acted only in self-defense and did what was necessary to subdue an out-of-control prisoner.

But what came next is indisputable. In a security video obtained by The New York Times, Mr. Strickland is seen in handcuffs, barely conscious and being dragged along the floor by officers, while a prison nurse standing close by does nothing. Even as he lies face down on the floor, near death, guards can be heard shouting, “Stop resisting.”

By the time an ambulance arrived, medical records described Mr. Strickland’s body as cold to the touch and covered in cuts and bruises, with blood flowing from his ears.

The 2010 case fits a troubling pattern of savage beatings by corrections officers at prisons across New York State and a department that rarely holds anyone accountable, issues that have been highlighted in a series of articles over the past year by The Times and The Marshall Project, a nonprofit news organization.

Mr. Strickland’s death was only briefly noted in local newspapers, and probably would have been forgotten by all but the officers and inmates. But the escape of two murderers from Clinton in June attracted extraordinary attention to the maximum-security prison, and details about its inner workings, long held secret, have started to reach outsiders.

Investigations by The Times uncovered the serious security lapses that made the escape possible, as well as beatings by guards during the interrogations that followed. State officials have said they are investigating the abuse claims, but there is little to indicate any results will come of it.

The internal affairs unit of the New York State Department of Corrections and Community Supervision has long been mired in dysfunction. Its former director of operations is awaiting trial on charges of sexually harassing several subordinates.

Officials with the State Police and the local district attorney’s office could not recall the last time charges had been brought against an officer at Clinton for excessive force, if ever, though inmates have filed scores of brutality lawsuits in recent years. The United States attorney for the Northern District of New York, which has jurisdiction over nearly half of the state’s 54 prisons, has not brought a brutality case involving a state corrections officer in at least five years, according to a spokesman.

In the Strickland case, the police and the district attorney concluded there had been no criminal wrongdoing, though two state prison watchdog agencies, the State Commission of Correction and the Commission on Quality Care and Advocacy for Persons With Disabilities, issued highly critical reports documenting numerous misleading and false statements by officers.

The dozen or so officers and medical personnel identified in the investigations either still work at Clinton or other state prisons, or were promoted or retired with full benefits. In the years since the Strickland case, several of them have again been accused of brutality by inmates.

The Times was able to piece together the story behind Mr. Strickland’s death by reviewing internal corrections department reports, log book entries and statements by the officers involved, along with the autopsy report and records by paramedics and emergency room doctors. Separately, six inmate witnesses were tracked down and interviewed at four prisons around the state.

Mr. Strickland’s death was only briefly noted in local newspapers, and probably would have been forgotten by all but the officers and inmates. But the escape of two murderers from Clinton in June attracted extraordinary attention to the maximum-security prison, and details about its inner workings, long held secret, have started to reach outsiders.

Investigations by The Times uncovered the serious security lapses that made the escape possible, as well as beatings by guards during the interrogations that followed. State officials have said they are investigating the abuse claims, but there is little to indicate any results will come of it.

The internal affairs unit of the New York State Department of Corrections and Community Supervision has long been mired in dysfunction. Its former director of operations is awaiting trial on charges of sexually harassing several subordinates.

Officials with the State Police and the local district attorney’s office could not recall the last time charges had been brought against an officer at Clinton for excessive force, if ever, though inmates have filed scores of brutality lawsuits in recent years. The United States attorney for the Northern District of New York, which has jurisdiction over nearly half of the state’s 54 prisons, has not brought a brutality case involving a state corrections officer in at least five years, according to a spokesman.

In the Strickland case, the police and the district attorney concluded there had been no criminal wrongdoing, though two state prison watchdog agencies, the State Commission of Correction and the Commission on Quality Care and Advocacy for Persons With Disabilities, issued highly critical reports documenting numerous misleading and false statements by officers.

The dozen or so officers and medical personnel identified in the investigations either still work at Clinton or other state prisons, or were promoted or retired with full benefits. In the years since the Strickland case, several of them have again been accused of brutality by inmates.

The Times was able to piece together the story behind Mr. Strickland’s death by reviewing internal corrections department reports, log book entries and statements by the officers involved, along with the autopsy report and records by paramedics and emergency room doctors. Separately, six inmate witnesses were tracked down and interviewed at four prisons around the state.

A majority of the inmates, like Mr. Strickland, are black and come from New York City, 300 miles to the south; they say they face a constant barrage of racial slurs.

Two years before Mr. Strickland’s death, another black inmate, Bradley Ceasar, died under similar circumstances.

Mr. Ceasar, 52, who was developmentally disabled, got into a confrontation with guards on Aug. 11, 2008, and within hours was dead. Officers and a nurse ignored his repeated pleas for help and provided no medical care, investigators said. An autopsy later determined that his ribs had been so badly broken that his lungs could not inflate properly, and he suffocated.

The department determined that the officers’ actions were appropriate, and in the end, the only person disciplined was a prison nurse, Beth Farnan, who was fined $500. She remains employed at Clinton.

Like Mr. Ceasar, Mr. Strickland was not known as a violent inmate. While many of the prisoners at Clinton are serving sentences for murder, rape and other brutal crimes, Mr. Strickland had been convicted of criminal possession of a weapon.

He had not committed a serious disciplinary infraction during his previous four and a half years in prison, according to state records. At the trial, Sgt. Betsy Whelden-Berglund said that for six months in 2009 she had overseen the cellblock where he was housed and had had no problems with him.

Mr. Strickland, however, did have a history of behaving erratically. By summer 2010, he had stopped taking medication for his schizophrenia, according to prison records. At various times, his mother, Selena Strickland, said, he claimed that he had had a baby, that he was God, that he was a millionaire and that he was married to Beyoncé. That August, when his mother last visited him, she said, “he was talking out of his head.”

On the morning of Oct. 3, 2010, the 44-year-old Mr. Strickland was upset that a guard had confiscated a plastic hand mirror, according to several accounts. Not long after returning to the cellblock from breakfast, he got into a disagreement with an officer.

From this point on, the stories told by guards and inmate witnesses diverge widely.

In the guards’ version, described at trial, Mr. Strickland argued with an officer, Casey Strong, after being ordered to gather his possessions and go downstairs to be locked into a new cell.

Among inmates, Officer Strong was considered trouble. He had a history of violent confrontations. Over an eight-year period he had been injured during fights with inmates and gone on disability leave three times, he testified at the November trial. He said that he had retired last summer, at 36, and was unemployed and collecting disability insurance.

Officer Strong asserted in his trial testimony that Mr. Strickland punched him in the shoulder during the dispute. To defend himself, Officer Strong said, he punched Mr. Strickland twice in the head and once in the chest. He said he grabbed the inmate in a bear hug, and they struggled and both fell down the concrete stairs.

Officer Strong was able to stop himself halfway down, he said, but Mr. Strickland fell to the bottom. Despite the fall, several officers said, Mr. Strickland was able to jump to his feet and start fighting with a second guard, Cory Liberty. According to the court testimony, Officer Liberty then punched Mr. Strickland several times, while Officer Strong used his baton to hit him in the back and legs repeatedly.

By then nearly two dozen officers, responding to a call for backup, had surrounded Mr. Strickland.

And still he continued to “struggle violently,” Officer Liberty contended. Only when four guards grabbed a limb each and pinned him to the ground was he finally subdued, several testified.

A prison accident report filed shortly after the episode listed only minor injuries to the officers, mostly bruises and pulled muscles. The two guards who had repeatedly punched Mr. Strickland also had swollen right hands. (Another officer later testified at trial that she had suffered broken ribs, but this was not mentioned in medical documents.)

The officers said Mr. Strickland had no visible injuries. Nor, they said, did he ever complain about being hurt.

In interviews, inmates said the guards were lying.

Three — Kevin Goode, Walter Maddox and Frank Povoski — said they witnessed Mr. Strickland being pushed, not falling, down the stairs. And three — Mr. Goode, Mr. Povoski and another inmate who asked not to be identified for fear of retribution — said they saw him lying, badly injured, at the bottom. Two said that after being beaten by several guards, he was dragged away screaming.

Accounts by prisoners are often viewed skeptically. But the six were all interviewed separately; five were serving time in four different prisons and the sixth had been released. Their versions differed in some details. One said the events unfolded after they came back from breakfast; another said it was after recreation. One prisoner said Mr. Strickland was handcuffed before he was pushed down the stairs; another said it was after.

But the basic story the men told was the same: Mr. Strickland was pushed down a flight of stairs, and then beaten nearly to death by a large group of guards.

Mr. Maddox, whose cell was on the same tier as Mr. Strickland’s, watched events unfold from about 25 feet away, he said. He recalled Mr. Strickland’s making a sound as though he was terrified when he was shoved down the stairs.

Mr. Goode was head porter on the cellblock, and he said he was buffing the floor at the foot of the stairway that morning. He said that before Mr. Strickland was pushed, an officer yelled a racial slur. As Mr. Strickland fell downward, Mr. Goode said, his skull hit the concrete steps several times. At the bottom he pulled himself into a tight fetal position, as about 10 officers took turns kicking him in the head and the ribs, Mr. Goode said.

They “beat this kid to zero,” he said.

Mr. Povoski, who watched from a floor above, said Mr. Strickland lay so still he assumed he was dead.

‘Is He Breathing?’

After a physical encounter with guards, inmates, as a matter of standard practice, are taken to the prison emergency room to be examined.

When Mr. Strickland arrived, the officers said, he resisted them, disobeying their orders, refusing to stand or walk, and repeatedly kicking them. They testified that they responded professionally, transporting Mr. Strickland from the prison emergency room to the mental health ward, and providing appropriate first aid.

The officers’ sworn statements bear little resemblance to the images captured that morning on the 45-minute video.

Investigators from the commissions of both correction and quality care reviewed the video and wrote reports that were highly critical of the guards’ response, as well as the medical care provided by the prison nurse. “Strickland did not resist the officers, nor was he out of control,” the quality care commission report said.

As the video begins, Mr. Strickland is seen wearing white boxer shorts and a brown T-shirt, torn across his left shoulder. A large, purplish bruise is visible. He is cuffed from behind and pressed against a cinder block wall by two officers, Terry James and Kevin Trombley.

“Inmate Strickland, you’re going to comply with a strip frisk, do you understand me?” said Sgt. Steven Sweeney, who was supervising.

Mr. Strickland looks unstable on his feet. His head is down. Over the next few minutes, he appears to grow weaker, at one point slumping over and trying to hold his head up with his right arm. It seems only the guards are keeping him from falling over.

Then he slumps to the floor.

The guards standing around him continue shouting throughout. “Stop resisting.” “Don’t push back.” “He’s still fighting.”

The lawyer for the Strickland family, John Seebold, contended that at this point in the video the officers were acting as if he was resisting to justify their brutal treatment of him earlier.

After five minutes, while Mr. Strickland seems barely conscious, the officers decide to take him upstairs to the mental health ward and give him an injection to calm him down.

There is a gurney a few feet away, but Officers James and Trombley grab Mr. Strickland by his arms, which are still handcuffed, and lift them until they are hyperextended behind his head. Then they drag him out of the room. (In Sergeant Sweeney’s subsequent report, he wrote, “I directed the officers to assist him to the elevator using professional techniques.”)

They drag him onto the elevator, take it to the third floor, then drag him off, dropping him face down in a hallway, still handcuffed. (“I again directed staff to assist inmate off the elevator in which staff complied,” Sergeant Sweeney wrote.)

While Mr. Strickland is left lying on the ground for more than two minutes, motionless, several officers step over him.

At 9 minutes 15 seconds into the video, someone is heard asking, “Is he breathing?”

For the next 35 minutes, as nurses and officers perform CPR, Mr. Strickland is unconscious and unmoving, yet remains handcuffed. (Asked at trial why the handcuffs were not removed, Sergeant Sweeney answered, “Medical’s involved, but he’s still a disciplinary problem for me.”)

The video concludes at 10:15 a.m., as Mr. Strickland is loaded into the back of an ambulance and the doors close behind him.

State investigators were scathing in their assessment of the medical response by the prison nurse, Robert Fitzgerald. A report by the State Commission of Correction said Mr. Fitzgerald “showed complete disregard of the obvious signs of a nonresponsive inmate.”

On the video, Mr. Fitzgerald is seen standing nearby and doing nothing as Mr. Strickland collapses onto the emergency room floor, and is dragged to the elevator.

Instead of riding in the elevator along with the officers to provide care for Mr. Strickland, Mr. Fitzgerald took the stairs. Again he is seen on the video off to the side, watching for nearly three minutes while Mr. Strickland lies motionless in the hallway of the mental health clinic, near death.

When asked during a deposition why he did not intervene sooner, Mr. Fitzgerald said he had to wait for Sergeant Sweeney to determine that the inmate was no longer a safety risk.

But when Sergeant Sweeney was asked during the trial why it had taken him so long to give Mr. Fitzgerald permission to treat the inmate, he said that the decision on when to intervene was Mr. Fitzgerald’s.

“Medical should have did something,” the sergeant testified.

Thirty-one minutes into the video, Mr. Fitzgerald can be heard complimenting an officer administering CPR. “You’re doing great,” the nurse says.

In reality, those present were doing a poor job, according to the medical experts who testified for the plaintiff and the defense at the trial. Because Mr. Strickland was handcuffed from behind the entire time, his back was not flat against the floor, compromising the effectiveness of the CPR, both doctors testified. And instead of continuously applying CPR, the staff took numerous breaks.

Not until the ambulance crew arrived, 30 minutes after Mr. Fitzgerald first noted that Mr. Strickland had stopped breathing, did he suggest removing the handcuffs.

“Is there any way we can get those cuffs off the back of him?” Mr. Fitzgerald asked an ambulance worker.

“I don’t think he’s going to go anywhere,” she answered.

The ambulance arrived at Champlain Valley Physicians Hospital at 10:40 a.m., and at 10:45 Mr. Strickland was formally pronounced dead.

The medical report by the ambulance crew detailed extensive injuries: bruises all over Mr. Strickland’s body, including his forehead, head, left cheek and shoulders; a missing tooth on the upper left side of his mouth; blood and clear fluid coming from his ears; bloody abrasions on both knees; and markings suggesting that something may have been placed around his neck.

The autopsy by the county coroner concluded that Mr. Strickland had died of cardiorespiratory arrest due to cardiac ischemia, meaning his heart could not get sufficient oxygen and ceased to function.

At the trial, the medical expert for the Strickland family, Dr. Alan Schechter, an emergency room physician at Montefiore Medical Center, testified that based on the autopsy results he believed Mr. Strickland died when his heart gave out from “stress induced by the altercation.”

“If he did not have the stressful events, he would not have had a heart attack,” said Dr. Schechter, who handles quality care reviews of emergency room deaths at Montefiore.

Had Mr. Strickland received the proper medical care, the doctor testified, “more likely than not he would have survived.”

Dr. Donald Doynow, an attending physician in emergency medicine at St. Peters Hospital in Albany, was the medical expert for the state. He testified that the coroner’s autopsy results were incorrect, and that the inmate had instead died from a condition known as Excited Delirium Syndrome.

It is a controversial diagnosis, viewed with skepticism by many in the medical profession. The syndrome is not listed in the current Diagnostic and Statistical Manual of Mental Disorders, nor is it recognized by the American Medical Association or the American Psychological Association.

It is, however, recognized by the American College of Emergency Physicians.

Dr. Doynow said studies had found that among the groups most vulnerable to Excited Delirium Syndrome were males who suffered from mental illness and stopped taking their medication. One of the most prominent symptoms, he said, is the loss of the ability to feel pain, which could explain how a prisoner might be able to repeatedly resist the physical restraints applied by corrections officers.

Dr. Doynow said the syndrome could bring about cardiac arrest.

When pressed about the syndrome, Dr. Doynow, who has been practicing medicine since 1988, testified that he himself had never seen a case of it.

At Clinton there is a committee of inmates designated to meet regularly with the prison management team as well as uniformed officers, to discuss issues of concern. Typically, the topics might include the handling of proceeds from bottle returns, or the distribution of stamps.

Not at the meeting held on Nov. 22, 2010. Mr. Strickland’s death, and brutality at the prison, were at the top of the inmates’ agenda.

Committee members complained that violence by the guards was out of hand. They asked that the administration provide them with a copy of the Strickland autopsy report and requested an investigation into the alleged beating of an inmate, Thomas Murphy, who they said had been badly injured 20 minutes before Mr. Strickland, by guards “wearing steel toe boots.”

Among the administrators present at the meeting were the prison’s superintendent, Thomas LaValley, and two of his deputies, along with Sergeant Sweeney.

According to the minutes of the meeting, the prison administrators responded that “all allegations of abuse are investigated,” and “when the autopsy is completed it will be public knowledge.”

Mr. Povoski, who was vice president of the inmates’ committee at the time, said the autopsy was never received and brutality at the prison continued, unabated.

In the years since, several officers involved in the Strickland case have been named in lawsuits filed by other inmates alleging brutality.

A suit filed last year by one inmate, Moshe Cinque Canty, claimed that a group of officers, including Sergeant Sweeney, handcuffed him, beat him and dragged him around by his dreadlocks. The officers shouted racial slurs, the suit claims. One guard yelled for the officers to pull the dreadlocks from Mr. Canty’s head and “choke the nigger with them,” the suit says.

According to Mr. Canty, who is serving time for attempted murder and robbery, when the beating was over Sergeant Sweeney told the others to straighten up their clothes, saying, “We have to look professional.”

In a legal filing, the officers denied all of Mr. Canty’s accusations.

Another pending suit from last year names Sergeant Sweeney along with Kevin Trombley, the officer who handcuffed Mr. Strickland and helped drag him to the elevator.

Edwin Banks, who is serving time for drug possession, said in the suit that Officer Trombley had repeatedly harassed him about his dreadlocks. One morning, after breakfast, according to Mr. Banks, Officer Trombley, Sergeant Sweeney and others severely beat him. Mr. Banks claimed that the sergeant then had the guards carry him by his limbs to the infirmary, with one officer grabbing his shirt collar so tightly that he passed out.

Lawyers for the officers have not yet filed a response to the accusations.

In each of these cases, inmates said they had filed grievances with the prison administration and written letters to Albany, including to the governor. Nothing came of them.

Within two weeks of Mr. Strickland’s death, several inmates said, they were questioned by the State Police and internal affairs investigators with the corrections department. Most said they did not know the names of the officers involved but would have been able to make identifications if they saw them again.

The Times has interviewed more than a dozen inmate witnesses in connection with several brutality cases in recent months, and not one had been shown photos of suspect officers by state investigators, they said.

Partly because the video evidence in the Strickland case was so compelling, investigators with the corrections department referred the case to the State Bureau of Labor Relations for possible departmental disciplinary action.

Nothing happened. The state agency that oversees licensing of medical professionals did not pursue the matter either.

The State Police concluded “that no criminal conduct of others contributed” to the death, and the Clinton County district attorney declined to present the case to a grand jury.

The officers and the nurse involved either continue to work for the corrections department or have retired with their full pensions. At the trial, Sergeant Sweeney said he left the department last May after 33 years of service, and is now working as a rural mail carrier.

The civil case is not likely to be resolved any time soon. Unless the parties settle first, the judge is expected to take up to a year to render his decision.

At a hearing this month in Albany, Daniel O’Donnell, the chairman of the State Assembly prisons committee, called for the creation of an independent oversight agency to monitor the state prison system. The meeting was adjourned, until an unspecified date, because the corrections department declined to testify.

During the civil trial, Mr. Strickland’s mother, a former nursing home aide who is 70 years old, testified that she used to try to make the six-hour bus trip from Brooklyn to visit her son once a month, but since he died she had moved to Georgia.

She was asked how she learned of her son’s death. She said a prison chaplain had called a minister that he knew in Brooklyn, who came to her house. She said that the next day, she phoned a counselor at Clinton to ask if there was any information about how her son had died. The counselor, she said, told her “no, because it was under investigation.”

There was no funeral, Mrs. Strickland told the court. “I had lack of funds.”

According to the death certificate, her son was buried on Oct. 15, 2010, in the Clinton Correctional Cemetery, a mile outside the prison wall.