Washington, June 18 (RHC)-- Four former Blackwater Worldwide security guards, who were put on trial last week in the U.S. over the 2007 killings of Iraqi civilians, faced a jury in the U.S. District Court for the District of Columbia -- Washington, DC -- on Tuesday.

In opening statements at the trial of Paul Slough, Evan Liberty, Dustin Heard and Nicholas Slatten, federal prosecutors told the jury that the guards shot first at a busy Baghdad intersection in 2007 and justified their actions later.

The guards opened their fire on a mother and her son in a white Kia, destroying the car and continuing to shoot indiscriminately as the guards traveled out of the intersection, prosecutors said. Assistant U.S. Attorney T. Patrick Martin said some of the victims were "simply trying to get out" of the way of gunfire from Blackwater guards. He said: "Fourteen died, 18 injured. For what?"

The Blackwater mercenaries had been charged with killing 14 Iraqi civilians and wounding 18 others using gunfire and grenades on September 16, 2007 in the Iraqi capital. Judge Royce Lamberth is overseeing the trial, which is expected to last several months. He has been a U.S. district judge for more than 25 years and he has a military background.

A large number of Iraqi witnesses are scheduled to testify in the case in what the U.S. Justice Department says is likely to be "the largest group of foreign witnesses ever to travel to the United States for a criminal trial."

Blackwater Worldwide, which is now known as Academi and is based in McLean, Virginia, is the most notorious private security firm that had operated in Iraq. Many Iraqis believe the U.S. military allowed Blackwater mercenaries to commit numerous war crimes in their country with impunity.