Five Blackwater Worldwide security guards have pleaded not guilty to manslaughter charges in the 2007 shooting deaths of 17 Iraqi civilians in Baghdad.
The Blackwater guards were arraigned in front of U.S. District Judge Ricardo M. Urbina on Tuesday.
The not guilty pleas were entered by former Marines Donald Ball, Dustin Heard and Evan Liberty; and Army veterans Nick Slatten and Paul Slough.
Prosecutors said the men unleashed a gruesome attack on unarmed Iraqis, including women and children.
A sixth guard - Jeremy Ridgeway of California - has pleaded guilty to one count each of manslaughter, attempted manslaughter, and aiding and abetting. He has agreed to cooperate with investigators.
In advance of the arraignment, the judge unsealed the arrest warrant for Ridgeway, reports CBS News producer Stephanie Lambidakis.
The government believes the document knocks down defense claims that the convoy was fired upon, reports Lambidakis. The government says they don't believe the radio logs released by defense lawyers in which a guard reports incoming fire. That guard was apparently in the "belly of the vehicle" and didn't see anything first-hand.
Blackwater radio logs made available to The Associated Press by a defense attorney in the case last month raised questions about prosecutors' claims that the guards' shooting was unprovoked. The log transcripts describe a hectic eight minutes in which the guards repeatedly reported incoming gunfire from insurgents and Iraqi police.
The North Carolina-based Blackwater is the largest contractor providing security in Iraq. Most of its work for the State Department is in protecting U.S. diplomats in Iraq. The company has not been charged in connection with the shooting. However, last month, an internal State Department report said Blackwater may lose its license to work in Iraq and recommends that the agency prepare alternative means to protect its diplomats there.