A military prosecutor branded four US soldiers "war criminals" as he pressed for them to face a court martial.
The US soldiers were all serving in the Samarra area
The men are accused of murdering three Iraqi detainees in cold blood close to the central city of Samarra in May.
The defence say the men were killed as they tried to escape, and argue there is insufficient evidence to proceed.
A senior US commander will now decide whether the case should be prosecuted. It is one of a series of murder allegations against US troops.
US investigators are currently also looking at the deaths of 24 Iraqis in Haditha last November, while four soldiers and an ex-serviceman face accusations of rape and murder over an incident in Mahmudiya, south of Baghdad.
Seven US marines and a navy sailor have also been charged over the death of a disabled Iraqi man on 26 April in Hamdaniya.
On Friday, three of the marines charged in the Hamdaniya case were additionally charged - along with three fellow marines - with assaulting civilians on 10 April.
The 10 April incidents are said to have come to light during the investigation of the 26 April case. The nature of the alleged assaults was not disclosed.
Friday was the last day of a pre-trial hearing in Tikrit required under US military law to decide whether the charges against the four men warrant a court martial.
Sergeant Raymond Girouard, Private First Class Corey Clagett and Specialists William Hunsaker and Juston Graber - all of the 101st Airborne Division - have been charged with premeditated murder and other offences.
The 101st Airborne Division was at the time involved in Operation Iron Triangle, targeting insurgents active in Salahuddin province and detaining hundreds of people. The deaths occurred during a search operation of a house near the Thar Thar canal outside Samarra on 9 May.
Prosecuting lawyer Capt Joseph Mackey claimed the defendants were cut free of plastic handcuffs and then killed without provocation.
"US soldiers must follow the laws of war... These soldiers did just the opposite," Capt Mackey said.
"They cut them loose and murdered them in cold blood. For this, they are not war heroes, they are war criminals. And justice states that they face trial."
'What they deserved'
All of the accused are refusing to testify on the grounds they may incriminate themselves, relying instead on statements made to investigators.
But the lawyer for Private First Class Clagett, Paul Bergrin, told the tribunal the defendants' claim was plausible.
"These detainees were able to break the flexcuffs, they had a knife and they were able to break free," he said.
"They attacked, they spun around, and they got exactly what they deserved," Mr Bergrin said about the detainees.
He claimed the prosecution witnesses had given inconsistent statements.
The decision on whether to proceed with the court martial now falls to the commanding general 101st Airborne Division, who is expected to rule in the next few days.