COLIN PERKEL/ASSOCIATED PRESS Three men the Pentagon says killed themselves were actually tortured to death by the CIA claims a Guantanamo Bay staff sergeant.

It was murder.

A staff sergeant at Guantanamo Bay claims to have solved one of the military prison’s greatest mysteries: Three men the Pentagon says killed themselves were actually tortured to death by the CIA.

The official government line was that Yasser Talal al-Zahrani of Yemen, and Salah Ahmed al-Salami and Mani Shaman al-Utaybi, both of Saudi Arabia, killed themselves in 2006 in a suicide pact.

Rear Adm. Harry Harris, the commander of the Joint Task Force Guantanamo, called the deaths “an asymmetric warfare committed against us.” The men were said to have hanged themselves.

Staff Sgt. Joseph Hickman, a Marine veteran who reenlisted in the Maryland National Guard after 9/11, contradicts the military version of events in his new book, “Murder at Camp Delta: A Staff Sergeant’s Pursuit of the Truth About Guantanamo Bay.” And he paints a sinister picture of the government’s use of the prison as a “battle lab” for cruelly inventive, experimental torture tactics.

Staff Sgt. Joseph Hickman, a Marine veteran who reenlisted in the Maryland National Guard after 9/11, contradicts the military version of events in his new book, ‘Murder at Camp Delta: A Staff Sergeant’s Pursuit of the Truth About Guantanamo Bay.’

“It is my informed opinion that there were three wrongful deaths at Gitmo on June 9, 2006, while I was on duty,” Hickman wrote.

The deaths of the three men — ages, 20, 30 and 37 — were a low point for Hickman, who was excited when his 629th Military Intelligence Battalion was deployed to Gitmo.

“Finally, at 41, I had my chance to meet the enemy,” he wrote.

Hickman proved his mettle early on in the deployment, leading a charge into a cell of rioting detainees who had soaped the floor and flung urine and feces at him and his men. When one of the prisoners came at them with a shank, he gave orders to fire a spray of 40-mm. rubber rounds that ended what had become a vicious fight.

FR VOLKER SKIERKA/FR VOLKER SKIERKA/PICTURE-ALLIAN Hickman wrote that he was already disturbed by conditions at the prison where Navy guards would routinely taunt the prisoners into a frenzy.

It was possibly the first time such an order had been given at Gitmo, and it earned Hickman a commendation for “exemplary leadership.”

But, Hickman wrote, he was already disturbed by conditions at the prison where Navy guards would routinely taunt the prisoners into a frenzy. While he harbored little innate sympathy for the detainees, whom he saw as America’s enemies, the “racism, the brutality, the chaos,” got to him.

One night, he stumbled on what was later confirmed as a secret CIA holding center, a “black site” that he nicknamed Camp No. There was a definite “disconnect between stated procedures and actual practices at Gitmo,” he wrote.

The night the prisoners died, Hickman headed the platoon guarding Camp Delta. At 6:30 p.m., standing in a north tower, he saw a prisoner escorted from Alpha Block into a white van with blackened windows. The van soon returned for another detainee.

The deaths of the three men — ages, 20, 30 and 37 — were a low point for Hickman (pictured), who was excited when his 629th Military Intelligence Battalion was deployed to Gitmo.

When the van returned a third time, Hickman raced to a vantage point where he could see where the van was going. Rather than turn right to the naval station, the van took the road leading to Camp No.

At 11:30 p.m., the van returned, this time heading for the medical clinic.

“Everything changed,” he wrote.

At 12:30 a.m., the camp lit up like a football field under the glare of lights, but, oddly, no alarms were sounded. Hickman questioned one of his men, who told him he had been ordered to alert a Navy chief in the mess hall that there had been a “Code Red.” No one knew what that was.

BRENNAN LINSLEY/ASSOCIATED PRESS Hickman surmised the three dead men had to be the ones he saw picked up earlier.

Hickman ran into a friend of his, a Navy guard, walking away from the clinic. Shaken, she told him that three detainees had just killed themselves. It was then she added a pertinent detail: “They had rags stuffed down their throats. And one of them was badly bruised.”

Hickman surmised the three dead men had to be the ones he saw picked up earlier. There had been no other activity at the prison camp throughout the night. He and his men were in position, in fact charged with observing anything that went on.

He learned from news reports that the official story was that the three men had hanged themselves in their cells in Alpha Block. Hickman and other guards were all too aware that if that were actually the case, they wouldn’t have witnessed the corpses being extracted.

The intense level of secrecy enforced at the camp prohibited Hickman from raising questions, but he fully expected to be asked for his report. Yet even during the Naval Criminal Investigative Service probe, Hickman says, he and his men weren’t tapped for their account, a complete break from military protocol.

He learned from news reports, such as the above one in the Daily News published on June 11, 2006, that the official story was that the three men had hanged themselves in their cells in Alpha Block.

The naval investigation confirmed that the men had committed suicide and further claimed they had fashioned dummies from bedding to fool guards into believing they were asleep in their bunks.

Hickman, according to the book, concluded that narrative was valid only “if each of the three men had been veritable Al Qaeda Houdinis able to (1) hoard materials; (2) fabricate them under the noses of guards into dummies and ropes; (3) partially cover their cells in ways that would make their hangings invisible to the guards; (4) make dummies that presented the illusion of skin and breathing movements, and (5) like acrobats, climb onto their sinks or cots, shove rags deep into their throats, bind their feet, affix their neck into their nooses, tie masks over their faces, bind their hands and then jump or fall from their perches — but silently so as not to attract the guards’ attention.”

The five guards assigned that night to patrol a 120-foot hallway were under routine orders to check the 27 detainees there every three minutes. Standard operating procedure, Hickman wrote, demanded that through the night they make visual contact with prisoners and determine if they were breathing. If any of those rules had been violated, cellblock guards should have been punished for dereliction in the aftermath. None were.

Hickman presents compelling proof that the detainees had no means of hoarding the materials to fashion nooses, bindings or dummies. Nor could they have hanged for two hours unobserved. Again, if there had been an emergency in Alpha Block that night, he and his men would have witnessed it.

BRENNAN LINSLEY/ASSOCIATED PRESS Hickman presents compelling proof that the detainees had no means of hoarding the materials to fashion nooses, bindings or dummies.

His account was more than buttressed by a 2009 report from the Center for Policy and Research at the Seton Hall University School of Law. Hickman, working as an Army recruiter in Green Bay, Wis., had contacted the director with his story, but Mark Denbeaux and his students arrived at their findings independently.

Even after a story in Harper’s Magazine by Scott Horton came out in 2010, “The Guantanamo ‘Suicides’: A Camp Delta Sergeant Blows the Whistle” and won a National Magazine Award, authorities made no move to reopen the investigation.

But Hickman and Denbeaux have continued their own inquiries and unearthed more documents that strengthen their case.

Hickman also found evidence that an anti-malarial drug, mefloquine, was routinely given to detainees arriving at Gitmo in doses high enough to induce a complete mental breakdown. An expert he interviewed equated the practice to “psychological waterboarding.”

BRENNAN LINSLEY/AP Hickman has immersed himself in dogged research and concluded that the decision to use Guantanamo Bay as a laboratory for torture techniques reached as high as Defense Secretary Donald Rumsfeld.

Hickman has immersed himself in dogged research and concluded that the decision to use Guantanamo Bay as a laboratory for torture techniques reached as high as Defense Secretary Donald Rumsfeld. He believes that the three men died after socks or a cloths of similar material were inserted into their throats as a precursor to wet-toweling, a simpler form of waterboarding that convinces the victim he is drowning.

The three detainees, low-level threats, one soon to be released, were dedicated hunger strikers. Hickman wrote that the camp authorities “hated hunger strikes” and fought them like low-intensity battles. For one thing, the rule was that hunger strikers couldn’t be interrogated.

Was the fear that they were about to incite another hunger strike — one had just ended — and the torture at Camp No a form of deterrent that resulted in accidental homicides?

Hickman is convinced that is the case, and says his book is an act of patriotic duty.

“I believe in American justice,” he wrote. “And I believe that the truth about June 9 must be revealed.”