The tape comes from Utah, but there are others from Connecticut, Florida, Texas, Arizona and probably many more. We found more than 20 cases of prisoners who've died in the past few years after being held in a restraint chair.
Two of the deaths we investigated were in the same county jail in Phoenix, Arizona, which is run by a man who revels in the title of "America's Toughest Sheriff."
His name is Joe Arpaio. He positively welcomes TV crews and we were promised "unfettered access." It was a reassuring turn of the phrase you don't want to be fettered in one of Sheriff Joe's jails.
We uncovered two videotapes from surveillance cameras showing how his tough stance can end in tragedy.
The first tape, from 2001, shows a man named Charles Agster dragged in by police, handcuffed at the wrists and ankles. Agster is mentally disturbed and a drug user. He was arrested for causing a disturbance in a late-night grocery store. The police handed him over to the Sheriff's deputies in the jail. Agster is a tiny man, weighing no more than nine stone, but he's struggling.
The tape shows nine deputies manhandling him into the restraint chair. One of them kneels on Agster's stomach, pushing his head forward on to his knees and pulling his arms back to strap his wrists into the chair.
Bending someone double for any length of time is dangerous; the manuals on the use of the 'restraint chair" warn of the dangers of "positional asphyxia."
Fifteen minutes later, a nurse notices Agster is unconscious. The cameras show frantic efforts to resuscitate him, but he's already brain dead. He died three days later in hospital. Agster's family is currently suing Arizona County.
His mother, Carol, cried as she told me: "If that's not torture, I don't know what is." Charles's father, Chuck, listened in silence as we filmed the interview, but every so often he padded out of the room to cry quietly in the kitchen.
The second tape, from five years earlier, shows Scott Norberg dying a similar death in the same jail. He was also a drug user arrested for causing a nuisance. Norberg was severely beaten by the guards, stunned up to 19 times with a Taser gun and forced into the chair where, like Charles Agster - he suffocated.
The county's insurers paid Norberg's family more than 4 millions in an out-of-court settlement, but the sheriff was furious with the deal. "My officers were clear," he said. "The insurance firm was afraid to go before a jury."
Now he's determined to fight the Agster case all the way through the courts. Yet tonight, in Sheriff Joe's jail, there'll probably be someone else strapped into the chair.
Not all the tapes we uncovered were filmed by the guards themselves. Linda Evans smuggled a video camera into a hospital to record her son, Brian. You can barely see his face through all the tubes and all you can hear is the rhythmic sucking of the ventilator.
He was another of Sheriff Joe's inmates. After an argument with guards, he told a prison doctor they'd beaten him up. Six days later, he was found unconscious on the floor of his cell with a broken neck, broken toes and internal injuries. After a month in a coma, he died from septicemia.
"Mr Arpaio is responsible." Linda Evans told me, struggling to speak through her tears. "He seems to thrive on this cruelty and this mentality that these men are nothing."
In some of the tapes it's not just the images, it's also the sounds that are so unbearable. There's one tape from Florida which I've seen dozens of times but it still catches me in the stomach.
