Amin al-Sheikh, a Syrian, said that US Army Specialist Graner laughed while physically hurting him and threatened more than once to kill him.

He said Specialist Graner forced him to violate his Muslim faith by making him eat pork and drink alcohol. He also told him to thank Jesus for keeping him alive.

Specialist Graner is being tried as the accused ringleader of the the abuse perpetrated by American soldiers at Abu Ghraib. He faces 17½ years behind bars if convicted on all counts of mistreatment and misconduct against him.

One of the charges against him arises from the claim that he jumped on Mr al-Sheikh’s leg after it had been wounded in a gunfight and struck it with a stick.

Asked if Specialist Graner appeared to enjoy inflicting pain, Mr al-Sheikh said: “He was laughing. He laughed. He was whistling. He was singing.”

On different occasions Specialist Graner was accompanied by an American soldier who urinated on Mr al-Sheikh and another who threatened to rape him while Specialist Graner was present, he said.

”Graner was the primary torturer,” Mr al-Sheikh said. “He was a naturally aggressive man.”

Guy Womack, for the defence, seized on Mr Sheikh’s evidence. He admitted going to Iraq in 2003 to fight US-led forces and was imprisoned in Abu Ghraib after being captured with AK-47 assault rifles, grenades and bomb-making materials.

While being kept at a tent camp next to Abu Ghraib Mr al-Sheikh persuaded an Iraqi guard to give him a pistol because he feared for his life. He then became involved in a gun battle with US soldiers. It was in this shoot-out that his leg was wounded.

Mr Womack said that the presentation of Mr al-Sheikh’s evidence was good for Specialist Graner. ”It was the face of the enemy,” he told the 10-man jury, made up of four officers and six soldiers, all of whom have seen service in Afghanistan or Iraq. Specialist Graner can be convicted on the vote of seven of them.

The defence has rested on the assertion that Specialist Graner was following orders from superiors. Some of Specialist Graner’s colleagues have painted a confused picture of whether there was an effective chain of command.

Specialist Joseph Darby, the Abu Ghraib whistle-blower, said Specialst Graner was an overpowering personality. “Most people wanted to be around or associated with him,” he said.

He quoted the accused as saying: “The Christian in me says it’s wrong, but the corrections officer in me says I love to make a grown man piss himself.”

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