Thomas Archambault, a law enforcement instructor and an expert on restraint techniques, said he thought US military policeman Charles Graner, had "used good foresight" in the way he dealt with the detainees.
He said piling the naked prisoners on top of each other was "a very creative technique". Defence lawyer Guy Womack earlier this week described the human stack as "a cheerleader pyramid".
Archambault, a former police officer who now runs a consultancy, said that given the circumstances, he saw nothing wrong either with the fact soldiers took pictures of the naked prisoners.
"Based on the stress these soldiers had gone through, a filthy stinking environment and the fact these prisoners killed American soldiers, I think I would have done the same thing," the former police officer said.
He said stacking up prisoners was a safe way to deal with a potentially dangerous situation, but admitted it did not appear in any training manual.
The jury was not present during his initial cross-examination on Wednesday morning, but heard Archambault after the judge, Colonel James Pohl, imposed some limitations on the specific issues on which he could testify.
Several more witnesses were to appear Wednesday as the defence attempted to demonstrate that Graner was just following orders to control prisoners and soften them up for interrogation.
One witness, fellow military police officer Ivan Frederick, said military intelligence officials praised the way the soldiers handled the detainees.
Archambault praised the way
prisoners were piled up
"They were telling us we were doing a good job," said Frederick, who was sentenced earlier to eight years in prison for his role in the Abu Ghraib abuses.
Graner, 36, has pleaded not guilty to the five charges, which include maltreatment of prisoners and assault, and which carry a maximum sentence of 17 and a half years' imprisonment.
On Tuesday, the court heard videotaped testimony from two Abu Ghraib detainees who described what they said was torture at the hands of Graner and other soldiers.
Amin al-Shaikh, a suspected Syrian fighter, said Graner beat him on bullet wounds he had sustained earlier. He said on one occasion, the soldier made him drink alcohol and eat pork, both forbidden for Muslims.
He singled out Graner as the "primary torturer", and said the military policeman evidently took pleasure in assaulting and humiliating prisoners.
Husayn Matar, an Iraqi jailed for alleged car theft, winced as he described how he was made to strip naked and masturbate in front of others and being hurled on to a pile of prisoners.
He said he recognised himself on some of the pictures of the abuses that caused worldwide outrage in April.
Graner, smiling and giving the thumbs-up sign appears on several of the photographs, which were presented as evidence at the court martial.
Asked by journalists outside the courtroom whether he felt any remorse about abusing detainees, the bespectacled soldier smiled and asked: "What detainees?"
The court martial is expected to finish by the end of the week.
It comes amid allegations that prisoner abuses also occurred elsewhere in Iraq, as well as in Afghanistan and at the US detention camp in Guantanamo Bay, Cuba.