Five Blackwater Worldwide security guards are expected to appear in federal court to answer to manslaughter charges in the 2007 shooting deaths of 17 Iraqi civilians in Baghdad.
The Blackwater guards will appear at an arraignment in U.S. District Court on Tuesday.
Prosecutors said the men unleashed a gruesome attack on unarmed Iraqis, including women, children and people trying to escape. But defendants contend they opened fire after coming under attack when a car in a State Department convoy they were escorting broke down.
The five guards are expected to plead not guilty to manslaughter and weapons charges in the shootings.
A sixth has pleaded guilty.
Blackwater is the largest contractor providing security in Iraq.