This seems like a contradiction: Put a dangerous prison inmate into solitary confinement, and then give him a cellmate. An investigation by NPR and The Marshall Project, a news organization that specializes in criminal justice, found that this practice — called double celling — is widespread in state and federal prisons. And as we learned, those cellmates often fight, attack and, sometimes, kill.

On Nov. 19, 2014, the door clanged shut behind David Sesson and Bernard Simmons. Sesson put his hands through the food slot to have his handcuffs removed. Both men were in "disciplinary segregation," a bureaucratic term for solitary confinement, at Menard Correctional Center in southern Illinois.

But unlike many in solitary, Sesson and Simmons wouldn't have a moment alone. The 4-foot-8-inch by 10-foot-8-inch space was originally built for one, but as Menard became increasingly overcrowded and guards sent more people to solitary, the prison bolted in a second bunk. The two men would have to eat, sleep and defecate inches from one another for nearly 24 hours a day in a space smaller than a parking spot, if a parking spot had walls made of cement and steel on all sides.

With a toilet, sink, shelf and beds, the men were left with a sliver of space about a foot-and-a-half wide to maneuver around each other. If one stood, the other had to sit. They could palm both walls without fully extending their arms. There was no natural light, just a fluorescent bulb and small Plexiglas windows that looked out onto the hall. The solid door muffled the cacophony of shouting and door-banging ricocheting off the tier. It also blocked ventilation.

The space itself appeared to be decomposing. The front wall, next to the door, was made of corroded metal. The paint on the wedge-shaped shelf had almost completely chipped away; the beds were caked in rust; and the floor underneath the toilet was stained brown and black. Dust and crumbs accumulated in every corner.

When guards locked the door, Sesson didn't know anything about Simmons — not his name, not what he had done to wind up in prison or what he did to end up in solitary. But Sesson says Simmons had heard a few things about him. He knew he was a "bug," someone who attacks his cellmates. And while Simmons was three inches taller, at 5 feet 7 inches, Sesson outweighed him by more than 100 pounds.

The two started arguing immediately. Each had to prove that he would not be messed with, because if something happened — if one attacked the other — there was no escape. The only way to alert a guard was to bang on the door and hope the sound could be heard above the din.

According to the videotaped confession Sesson gave investigators with the Illinois Department of Corrections, he says Simmons told him he was serving a life sentence for murder. Sesson said he was, too. That settled it. Neither had anything to lose.

Sesson thought he had made it clear to the guards that he did not want a cellmate. After years of sharing claustrophobic cells with strangers, he told them that he would hurt anyone they put him with; that's how desperate he was to be alone.

"Frankly, I am tired of living with people," he said later. So he told Simmons, "If we get into it, I'm not gonna stop."

Later that day, they ate dinner on their beds and tossed the empty Styrofoam trays and milk cartons in the corner. Then an officer's face appeared in the small window in the door. He called both their names for the 9 p.m. count, and after they replied, he moved on to the next cell. That's when Sesson jumped down from the top bunk.

Sesson says Simmons threw the first punch, only grazing Sesson's face. Sesson lunged back at him and grabbed him by the throat, wrestling Simmons to the ground. Sesson says he picked up a torn, knotted strip of bedsheet, but it split. So he pulled a shoelace from his boots and wrapped it tightly around Simmons' neck.

The men in the cell next door told investigators, according to a Department of Corrections written account, that they heard a few minutes of muffled fighting through the concrete walls and banging on the door. Then, quiet. The prison staff heard nothing. It took at least 30 minutes, when a corrections officer made his next round, for someone to check on cell 6-38.

"My cellie is dead. I killed him," the officer says Sesson told him. Simmons' body lay on the ground, halfway underneath the bottom bunk.

They had been together less than six hours.

Solitary's 'Terrible Price'

In recent years, the practice of solitary confinement has faced unprecedented criticism. "It doesn't make us safer. It is an affront to our humanity," President Obama wrote in an op-ed in the Washington Post in January, when he announced a set of reforms to solitary in federal prisons. Both the pope and the United Nations have classified it as torture, and in June 2015, Supreme Court Justice Anthony Kennedy wrote that "years on end of near-total isolation exact a terrible price."

Prisoners have described how isolation has pushed them toward insanity. Some lost the ability to focus, to interact with people, or to differentiate the real from the imagined. Multiple studies have found inmates in solitary are more likely to hurt themselves or attempt suicide than those in general population. And it doesn't end when they're set free. Those released directly from solitary to their homes have difficulty maintaining relationships or holding down jobs. Many end up right back in prison.

In all this discussion about the harmful effects of segregation, solitary is often described as the isolation of one person in a cell, ignoring the many who, like Simmons and Sesson, are locked in a tiny room together for nearly 24 hours a day. While there are no national statistics on the number of people confined in double-cell "solitary," at least 18 state prison systems double-up a portion of their restrictive housing, and over 80 percent of the 10,747 federal prisoners in solitary have a cellmate.

In many places, prisons have turned to double celling to cope with overcrowding. "If you can come up with a better way to do this, understanding the fact that we are 162 percent of capacity without double celling, I'm willing to listen to you," an Illinois Corrections Department spokesman told reporters and mental health advocates in 1994, when the state faced criticism for doubling up the mental health units at Menard. Illinois is under particular pressure as one of the most over-stuffed prison systems in the country.

"We've done this utterly bizarre thing, which is to put two people in cells that were built for one and leave them both in there for 23 or more hours a day," says Craig Haney, a psychologist who has studied solitary for more than 30 years. "The frustration and anger that's generated by being in isolation is intensified by having to navigate around another person's habits, trials and tribulations."

Eddie Caumiant, the regional director of the American Federation of State, County and Municipal Employees union that represents Menard's correctional officers, says he's heard double celling described as a "powder keg" and "an accident waiting to happen."

The cells are more cramped, the inmates' movements more limited. There's the unrelenting pressure of living with another, potentially mentally ill or dangerous person — a pressure that can fester into paranoia and rage.

"You never know what to expect from a crazy person because there are so many types of crazy," Daniel Delaney wrote in a letter to The Marshall Project. Delaney is currently at ADX Florence in Colorado, convicted of killing his cellmate in solitary in 2010 at another federal prison. "A lot of crazy people don't shower or clean up after themselves. Some make funny noises. Some just tear out pages from books and turn 'em into little pieces of paper confetti. And, of course, some crazy people are violent."

Despite the risks of double celling, some corrections officials insist it's preferable because it's technically not "solitary" at all. In Texas and Indiana, prisoners who are locked down for nearly 24 hours a day, but with a cellmate, are not classified as being in "segregation." When Charles Samuels, then director of the federal Bureau of Prisons, was asked how many people were kept in solitary during an August 2015 Senate hearing on federal prison conditions, he said: "We do not practice solitary confinement. ... When in­di­vidu­als are placed in re­strict­ive hous­ing, we place them in a cell with an­oth­er in­di­vidu­al."

The presence of that other individual, says Edmond Ross, a spokesman for the federal Bureau of Prisons, can prevent prisoners from committing suicide.

"It's better to have two individuals in restrictive housing instead of one. ... It's less likely that individuals harm themselves," he says. But while having a cellmate may decrease the risk of self-harm, it increases the risk of inmate-on-inmate violence.

"There have been rare instances where individuals have attacked their cellmates and, in a few instances, murdered their cellmate," Ross says.

In Menard, double-celled prisoners are placed in rooms that are a foot-and-a-half narrower than those in general population (too narrow, one inmate has said, to do push-ups). Gerard Schultz, who was double celled at Menard for a cumulative eight months, explained in a letter that he had to create a schedule with his cellmate to determine when someone could stand up. Alan Mills, the executive director of the Uptown People's Law Center, a Chicago legal nonprofit, reported meeting two double-celled prisoners who had developed bedsores from lack of movement.

Inmates in the segregation unit receive two showers and nine hours of recreation time each week, according to prison officials (inmates, lawyers and advocates claim it is often far less). Check-ins with medical and mental-health staff often take place through the cell door, forcing prisoners to report intimate physical and psychological problems in front of their cellmates, or not at all.

Across the country, double-celled inmates have lashed out against crowded conditions in extreme ways.

One prisoner, Aaron Fillmore, started feeling an unexplainable aggression toward his cellmate. "It was a level of discomfort that I never experienced before," he wrote in a letter. Fillmore was double-celled at Lawrence Correctional Center in Illinois for three months. "I had thoughts of just punching him in the face. Why? I have no idea. I just had the urge to do it."

In 2013, an Ohio man suffering from psychotic delusions strangled his cellmate a day after they were placed together. The murdered cellmate was two days away from being released. A prisoner in Georgia stabbed his cellmate multiple times in 2014 as officers were handcuffing that cellmate through the cell door. When guards demanded that the prisoner put his hands up to be cuffed, he yelled in response, "I can't do that. He just kept messin' with me." That same year in Alaska, two cellmates who had been friends got into an argument, which ended when one strangled the other. After realizing what he had done, he screamed for the guards' help.

Re-entry advocate Johnny Perez, who says he spent a cumulative 16 months at Upstate prison in New York, said some prisoners would tell officials they were thinking of hurting themselves just to be put on suicide watch, away from their cellmates. "They take your clothes, give you a smock," he says. "People call it 'going on vacation.' "

'Move My Cellie'

Ten years before Sesson killed Simmons, Corey Fox killed his cellmate, Joshua Daczewitz, in the same segregation wing of Menard. Daczewitz was an overweight 22-year-old who grew up in a suburb of Chicago. Court records show he had never been to prison before and was serving a seven-year sentence for arson and robbery. He landed in solitary at Menard after testing positive for crack cocaine.

Fox, then 28, was serving a life sentence for murder. He had been in single-cell solitary at Pontiac Correctional Center for attacking a former cellmate and telling a social worker he fantasized about dismembering him, state investigation documents show. He was then transferred to Menard — and double celled.

After Fox and Daczewitz were placed together, Fox repeatedly asked guards to remove his younger cellmate. Even though he was somewhat friendly toward Daczewitz (playing chess, sharing magazines, introducing him to a female pen pal), Fox said he needed to live alone. "Being housed in solitary confinement with another person, unable to escape that person's presence, habits or tactics, is like wearing a corset made of nails and explosives, constantly," Fox wrote in a letter to The Marshall Project.

After two months of begging for a single cell, Fox told an investigator he wrote a note to guards, which said: "Move my cellie or I'm going to erase him."

They didn't, so he did.

In careful cursive, he wrote guards another note, which was included in investigation documents by the Illinois Department of Corrections obtained by NPR and The Marhsall Project: "As unbelievable as it may sound ... my cellmate, Joshua Daczewitz, is dead, deceased, no longer breathing, finished, on the other side, and so on and so on. ... You are welcomed to come directly to my cell and view the body if you believe this all to be a joke."

Fox pleaded guilty to the murder and received a second life sentence. He also received a single cell at Tamms Correctional Center, a supermax prison in Illinois. When Tamms closed in 2013, he was moved back to a single cell at Pontiac. Daczewitz's mother won a $13 million lawsuit against Fox, and a separate settlement against the state for putting her son in the cell in the first place.

On a tour of Tamms in 2009, Sen. Dick Durbin, D-Ill., met Fox. During their brief conversation, Fox told Durbin how and why he killed his cellmate.

"It would seem to me to be fair warning if a prisoner who has been in solitary says, 'If you put someone in this cell, I'll kill 'em.' It's a danger to any inmate that's put in there," Durbin tells NPR and The Marshall Project. "Here we have a horrible situation, solitary confinement, made even worse by the possibility that that cellmate is going to be an attacker." Durbin has since led two Senate Judiciary hearings on how to rethink solitary.

After the Chicago Tribune dug into both Daczewitz's murder and a similar killing at Stateville Correctional Center — where a double-celled convicted murderer strangled his cellmate in his sleep — Illinois prison administrators created new guidelines to prevent future casualties. They started requiring officers to consider inmates' crimes, size, gang affiliations and behavior when assigning cellmates.

The ultimate decision as to whether to place two prisoners together, however, remained at the discretion of the staff. Someone who had previously attacked or threatened a cellmate could still be doubled up.

"We should know better than to put folks who have a demonstrated proclivity for violence together in double cells," says Caumiant, the union spokesman. But he says overcrowding makes the practice unavoidable.

It's a necessity that has come under fire in Illinois in recent years. In June 2015, the Uptown People's Law Center and the firm Winston and Strawn LLP filed a federal lawsuit against the state for sending 2,300 people to single- and double-cell solitary, hundreds of whom had been there for over a decade. Illinois corrections spokeswoman Nicole Wilson did not comment on the lawsuit but said the department is currently reviewing its use of segregation.

In 2014, Sesson was the fourth man in less than two years to murder his cellmate in Menard's solitary unit. By comparison, there were only nine reported homicides in all of Illinois' prisons in the previous 11 years.

"I really think that the employees of Menard do the best that they can. And, quite frankly, do a good job [because] we don't have more [murders]," says Randolph County State's Attorney Jeremy Walker, who prosecuted the four recent murders. "But it's a tough place to do time. People that say cons have it easy, they ain't never been in Menard."

'You're Asking For Disaster. You're Asking For Death.'

Menard Correctional Center sits on the northeast bank of the Mississippi River in Chester, Ill. From the outside, the prison, which opened in 1878, looks more like an ornate university building than a maximum-security facility. Stone lions are perched at the entrance, and columns prop up an awning carved with Victorian skeleton keys and the scales of justice.

The segregation wing is on the north side of the building and includes 143 double cells. While prisoners often complain about their cellmates, and many would prefer a single cell, space is limited. Officers have to parse which threats are empty, and which are not. "Cons have a way of working the system. That's usually why they're down there," says Walker, the state's attorney. "Just because they said 'I don't like my cellie' or 'I'm going to do something to my cellie,' it would be very difficult to move them every time."

Corrections officers speculate that the situation at Menard worsened in January 2013, when then-Gov. Pat Quinn shuttered Tamms. Officers believe that closing the prison exacerbated overcrowding, and the fear of being sent to Tamms kept inmates from violent outbursts. "The deterrent we had before isn't there, and the inmates are acting like it," one union official said in a newsletter in June 2013.

There's no way of definitively knowing why the surge in murders happened when it did, but what is clear is that tension on Menard's north tier finally exploded in 2013. Court documents show the first of those murders happened the night of Jan. 25, 2013. Donald Hazzard, a young prisoner who had previously assaulted other inmates, beat his older cellmate, Yusuf Abuzir. Abuzir died of his injuries a month later, at the age of 64.

Hazzard said in a videotaped confession that he attacked because he felt threatened. "He was a striker, more of an older intimidator. I'm looking like I'm watching my back," he told investigators. In a taped confession, Hazzard's sentences trail off and his mouth twitches occasionally. "I've met a lot of homies [who] got stabbed up and raped in the joint just for being on the bottom bunk," he said. Hazzard was ultimately found not guilty by reason of insanity. He is now in a high-security mental health facility.

Six days later, it happened again. Officers pulled a struggling, angry prisoner out of his cell in handcuffs, followed by the lifeless body of a 25-year-old man, according to court records. The victim, Jason Hall, had bruises all over his face and a broken nose. There were scrapes on his left cheek from trying to pry off his cellmate's fingers. Hall had been sentenced to 13 years for carjacking and was two years away from going home. His cellmate, James Amison, pleaded guilty to the murder and received another 50 years in prison. He is now housed at Pontiac.

Two months after that, in March 2013, Frank Wings stopped an officer as he was making his 9 p.m. rounds and told him: "My cellie tried to stab me, then I choked him," a prison investigation report says.

Corrections officers handcuffed Wings and removed him from the cell. Then they handcuffed his dead cellmate before attempting CPR. It was too late. William Crowder died of manual strangulation at the age of 35. Wings pleaded guilty to second-degree murder, claiming self-defense, and received another 20 years in prison. In a letter to The Marshall Project, Wings said he had asked officers to move him the night before because his cellmate had started "acting strange." But "they didn't respond at all."

Two days later, Crowder's sister, Emmerine, received a call from the prison. Her brother was dead. Though Emmerine knew her brother was in and out of "lockdown," she didn't know that he had been double celled until he died.

"I thought segregation meant you was by yourself," she says. "It don't make no sense to me. You're asking for disaster. You're asking for death."

Sesson And Simmons Seemed Compatible

The Illinois Department of Corrections will not say exactly how long Simmons and Sesson had been double celled before they ended up together, or why they were sent to solitary in the first place. (Once an inmate is placed in segregation, it is easy to rack up additional disciplinary infractions and be kept there for months or years.)

Wings and Sesson agreed to be interviewed for this story, but the Illinois Department of Corrections denied access. Spokeswoman Nicole Wilson said she could not comment on specific cases, and did not discuss the policy and rationale behind double celling. As of March 15, the Illinois Department of Corrections reports having 50 inmates in double-cell solitary at Menard.

What is known about Simmons and Sesson is that they both had multiple cellmates at Menard by the time they were locked together in cell 6-38 — and that Sesson's patience was fraying.

Simmons' most recent disciplinary ticket was for disobeying a guard's orders. Sesson's was for trying to strangle his last cellmate with a television cord 11 days before he killed Simmons.

Sesson and his previous cellmate were allegedly fighting over space. "He kept crowding me ... was gonna boss me around," Sesson said, according to reports from prison investigators. Sesson pinned his cellmate to the ground and pulled the television cord tightly around his neck. Someone walked by in time and yelled at Sesson to knock it off. Sesson let go of the cord.

His cellmate was alive but had to remain locked in a room with a man who had just tried to kill him. Staff interviewed Sesson's cellmate, who told them that he was "afraid to say anything at first," but after a day of nonstop arguing, "he started to fear for his life." The two were separated immediately, and Sesson received a disciplinary ticket for more time in solitary.

Sesson and Simmons seemed compatible on paper. They were the same age (34) and from the same area (South Side of Chicago). They'd both been in prison before on various charges and were now serving life sentences for murder. Sesson had shot two men in 2002 after one objected to a homophobic comment Sesson made, according to a Cook County state's attorney. Simmons was sentenced to life without parole for stabbing his parents in 2009. Simmons' sisters believe the murders happened during a psychotic break; that day, he told one sister he was God and called for "death to nonbelievers."

But Sesson told the prison that no matter whom they paired him with, he would attack again. In his confession to investigators, he said: "I've been down here since 2004. Everybody always trying to find someone to match up with me," he told investigators. "They say I'm a bug, that I fight with all my cellies. So I guess I rub everybody the wrong way."

The Simmons family was furious with the prison's decision to ignore Sesson's warnings and past behavior. "They knew this and they put our brother in there with him anyway?" says Simmons' sister Debra. "My brother was collateral damage for him to get his one-bedroom unit."

Sesson pleaded guilty to the murder and was sentenced to 40 more years in prison on top of his life sentence. He is now housed at Pontiac.

Before he was escorted out of court for the last time in July, the judge asked Sesson if he had any questions. "No," he said. "I apologized, but I just had to get up out of there."

Saying Goodbye To Their Brother

For months after Simmons' death, his sisters had no idea why their brother had been killed. Debra Simmons, who watched all the prison shows on MSNBC, figured he had been targeted because of an old grudge or where he was from. It wasn't until she spoke with prosecutor Jeremy Walker that she learned why Sesson lashed out.

"He said it was just as simple as the cellie didn't want a roommate," Debra Simmons says.

The more the Simmons sisters found out about Menard, the more they felt the prison was responsible for their brother's death. They tried to find a lawyer to file a wrongful death lawsuit, but no firm would take the case. Then in November 2015, the civil rights firm of Kathleen Zellner, who recently made headlines for representing Steven Avery from Making a Murderer, signed on. The family filed a federal suit on March 18 against Menard warden Kim Butler and other employees, alleging cruel and unusual punishment.

"My brother was not a saint. But he was blood," Debra Simmons says. "They turned the key, and my brother walked to his own execution."

Debra Simmons claims that to this day, the corrections department has not called her about her brother's death. When she wanted to bring Simmons back to Chicago, she had to reach out to funeral homes near the prison looking for his body. She discovered that her brother had been sent to a mortuary to be cremated and buried alongside unclaimed remains. A month later, she received his ashes in the mail in a small cardboard box.

On April 14, 2015, which would have been Simmons' 35th birthday, his family returned to the oak tree in Washington Park in the South Side of Chicago where they had scattered their parents' ashes seven years ago. There, box in hand, they said goodbye to their brother.

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