The men signed documents in Arabic - a language none of them understands - after being threatened by having guns put to their heads and in Williams' case, having electric shocks administered to the testicles, Reprieve lawyer Marc Calcutt said.
In a draft witness statement provided to Mr Calcutt, Williams said: "I remember that the police put a towel on my face so I could not see. They kept telling me I was going to die. I was so scared.
"Once I had been knocked to the ground, the police picked me up and put me on the bed. They pulled down my trousers, spread my legs and started to electrocute my testicles. It was unbelievably painful. I was so scared.