The defence of a US soldier accused of leaking huge amounts of classified material opened with a video he leaked showing a US helicopter crew laughing as they shot dead civilians and journalists in Baghdad.
The video has become an infamous example of US military malpractice after it was leaked along with thousands of classified documents by former intelligence analyst, Bradley Manning.
Defence lawyer David Coombs began by offering the video as evidence.
The court-martial watched 38 minutes of footage taken from the camera of an Apache gunship as it circled a neighbourhood of Baghdad in 2007.
The crew discussed a group of 11 men they considered armed as hostile, before shooting at them with the Apache's cannon.
They laugh and call the men "dead b******s". The men were unarmed and included two journalists from the Reuters news agency.
Coombs said that a transcript of the video had been made public in a book, The Good Soldiers, by Washington Post journalist David Finkel, before WikiLeaks published it.
The US government has charged Manning with aiding the enemy with the release of the material, and specifically the video of the Baghdad attack. Manning faces life in prison if convicted of that charge.
The court-martial also heard that there was nothing to stop Manning from installing software for the high-speed download of secret State Department cables, the witnesses said.
Coombs sought to portray a military atmosphere that allowed intelligence analysts like Manning to listen to music or watch films stored on a classified hard drive or personal computer while on duty.
Captain David Lim, one of Manning's supervisors, said he had encouraged analysts to delve into State Department cables and other classified materials to avoid "tunnel vision".
Lim and Chief Warrant Officer 2 Joshua Ehresman said there was no oversight at Manning's Iraq outpost on installing executable files on the Army computers that had access to classified materials.
An executable file contains a programme that is ready to be run or carried out. Manning is accused of installing one to allow the downloading of more than 250,000 State Department files at a rate of 1,000 an hour.
Under prosecution cross examination, Lim said the State Department files were labeled classified and he had not let Manning install the executable file.
Manning is charged with leaking the files while serving in Iraq in 2009 and 2010. The charges include espionage, computer fraud and aiding the enemy by giving al Qaeda access to US intelligence through WikiLeaks, an anti-secrecy website.
The defence has sought to portray Manning as a naive but well-intentioned soldier who wanted to show Americans the reality of war in Iraq and Afghanistan. The prosecution rested last week after five weeks of evidence, some in closed session.