But Sergeant Santos Cardona's defence lawyer said his client had done nothing wrong, and branded the jail a "zoo" where low-ranking soldiers faced extreme pressure from superiors despite a chaotic chain of command.
A seven-member panel of four officers and three enlisted soldiers serving as a jury at the vast Fort Meade military base outside Washington, will reopen deliberations on the case after meeting for nearly three hours after hearing final arguments on Tuesday.
The court martial was the latest prosecution of a soldier over the Abu
Ghraib scandal, described by President George W Bush last week as America's "biggest mistake" in Iraq.
It took place as a possible new and separate scandal loomed, as scrutiny mounted in Washington over reports of alleged killings by US troops of civilians in the the Iraqi town of Haditha.
Sgt Cardona, a military policeman, faces a possible 16-and-a-half years in jail if convicted on charges of assault, dereliction of duty, conspiracy and making a false statement after the week-long court martial.
In his dramatic summing up, lead prosecutor Major Christopher Graveline showed panel members a picture of a naked Iraqi prisoner, cowering from two dogs against a wall in the jail, once used as a torture chamber by Saddam Hussein's regime.
"If this was an American soldier in the hands of some of our captors, would we consider that mistreatment?" Maj Graveline asked.
Maj Graveline rejected defence arguments the pictured encounter reflected force necessary to subdue a violent prisoner.
He also alleged that Sgt Cardona and a comrade had hatched their own "mission" to terrify prisoners.
"(They) were playing a game with their military working dogs, a game that the sole purpose was to get the detainees in those cells to piss on themselves, to shit on themselves," he alleged.
Maj Graveline claimed that Sgt Cardona had used his Belgian shepherd dog effectively as a weapon, and allowed it to bite prisoner Mohammed Bollendia.
"It is the same as if they would have shot him in the leg. They were doing their own thing, for their own entertainment,” said Maj Graveline.
Sgt Cardona's lead counsel, civilian attorney Harvey Volzer, suggested throughout five days of testimony that his client's superior officers condoned the use of dogs in interrogations at the jail outside Baghdad.
On Tuesday, he took aim at conditions in the camp, describing the command structure as "clear as mud," saying military policemen were not given explicit orders how to use dogs.
The Abu Ghraib scandal erupted in early 2004 after photographs were leaked to the press showing US guards mistreating and sexually humiliating prisoners. Some pictures showed naked prisoners cowering before unmuzzled dogs.
Seven lower ranking soldiers, described by US Defence Secretary Donald Rumsfeld as "a few bad apples", have faced courts martial.
Specialist Charles Graner and his girlfriend of the time, Private Lynndie England, became the public face of the abuse scandal. Both have since been convicted and sentenced to prison by military courts.