The United States brought new manslaughter charges on Thursday against four former Blackwater Worldwide security guards for a 2007 shooting in Baghdad that prosecutors said killed 14 unarmed civilians.
The shooting caused tension in U.S.-Iraqi relations and raised concerns about the U.S. government's use of private contractors, who were shielded from prosecution in Iraq.
The original U.S. charges filed against the Blackwater guards in 2008 were thrown out in December 2009, about a month before a scheduled trial. A U.S. District Court judge ruled that prosecutors should have done more to exclude statements that the guards gave under threat of losing their jobs.
The case was reinstated in 2011 and prosecutors began a lengthy review of what charges they could prove in court.
The new indictment returned by a grand jury in Washington charges 33 counts, including voluntary manslaughter, attempt to commit manslaughter and using a firearm in a crime of violence.
The guards had pleaded not guilty to the nearly identical charges brought five years ago. They are Paul Slough, 34; Nicholas Slatten, 29; Evan Liberty, 31; and Dustin Heard, 32.