Four British soldiers forced an Iraqi teenager into a river at gunpoint and watched him drown "to teach him a lesson", a court martial has heard.
All four men deny manslaughter
Ahmed Jabber Kareem Ali, 15, could not swim and they allegedly watched him struggle in "obvious distress" in the Shatt al-Basra canal in May 2003.
They then fled the scene, heard the court martial in Colchester, Essex.
The three soldiers from the Irish Guards and one from the Coldstream Guards all deny manslaughter.
Prosecution counsel Orlando Pownall QC described the cause of death as the "unlawful and dangerous activities of the four defendants acting together as part of a joint enterprise".
He told the court martial the incident was "a common design or plan to force the alleged looters into the water to teach them a lesson".
The four men standing trial are Sergeant Carle Selman, 39, then of the Coldstream Guards and now serving with the Scots Guards, Lance Corporal James Cook, 22, Guardsman Joseph McCleary, 24, and Guardsman Martin McGing, 22, all of the Irish Guards.
The seven-strong military panel heard the men had assisted the Iraqi police in detaining four alleged looters on 8 May 2003.
The soldiers have been accused of taking the suspects to the banks of a canal in a British Warrior vehicle where they forced them to enter the water at gunpoint.
The prosecution referred to claims made by Aiad Salim Hanon, one of the suspects, who said he and Mr Kareem - an asthmatic - were forced into the water and had stones thrown at them.
"Kareem was in obvious distress as he was unable to swim," said Mr Pownall.
"His head bobbed to the surface and then disappeared. One of the soldiers who was on the bank of the canal made as if to remove his clothing in order to rescue Kareem, but then returned to the Warrior tank, which drove away."
The court heard that Mr Kareem's body was found almost two days after the alleged incident at the canal which would have been at least two metres (6ft) deep, with a current and an uneven waterbed.
Mr Pownall said post-mortem tests suggested there was "nothing to indicate signs of injury that might have caused his death apart from what is suggested to be an irresistible inference that Kareem had drowned".
The prosecution counsel also argued that three of the defendants gave accounts which were inconsistent with each other.
Looting in Basra was of "epidemic proportions", said the prosecution, adding that that there was no real guidance as to how best to deal with the problem.
"It might be said, as has been reported elsewhere, that the coalition forces were ill-prepared for the occupation in Iraq and maintenance of the peace and received insufficient guidance," said Mr Pownall.
He went on: "It is the Crown's case that the activities of the four accused fell significantly and unlawfully outside what could be described as minimum necessary force. There was no need to use any force at all.
"That is not what happened and the consequences of that is that a 15-year-old died needlessly and unlawfully."
The hearing has been adjourned until Wednesday.