In the first public airing of an investigation that remains a source of international outrage, the Justice Department unsealed its case against five private security guards, built largely around the chilling testimony of a sixth guard about the 2007 shootings that left 17 unsuspecting Iraqi civilians dead at a busy Baghdad traffic circle.

In pleading guilty to manslaughter, the sixth security guard, Jeremy Ridgeway of California, described how he and the other guards used automatic rifles and grenade launchers to fire on cars, houses, a traffic officer and a girls' school. In addition to those killed, at least 20 people were wounded.

The six guards were employed by Blackwater Worldwide, the largest security contractor in Iraq; the company, based in North Carolina, has not been charged in the case.

Ridgeway said in the court documents unsealed Monday that the episode in Nisour Square on Sept. 16, 2007, started when the guards opened fire on a white Kia sedan "that posed no threat to the convoy."

He told investigators that although he could not clearly see the front passenger in the Kia, he noticed that the passenger was moving his arms, according to the documents
Defendant Ridgeway then fired multiple rounds from his M-4 assault rifle into the front passenger's side windshield of the white sedan, killing the passenger," the documents read. The statement went on to say that even after it was clear the driver of the sedan had been killed, several others in the convoy continued to fire on the car, and at least one of them launched a grenade.

After the car was in flames, according to the statement, "Defendant Ridgeway recognized that there had been no attempt to provide reasonable warnings to the driver of that vehicle."

The five guards named in the indictment rejected those assertions, and, in a legal move aimed at challenging the venue for the case, they surrendered to U.S. authorities in Salt Lake City, Utah, which is considered a more conservative, pro-military part of the country than Washington, where the Justice Department made public its case.

The indictments and the defendants' cross-county legal maneuver set the stage for the first test of the government's ability to hold private security contractors accountable for what it considers crimes committed overseas. They are also likely to produce protracted arguments on technical matters aimed at scuttling the case well before a jury has the opportunity to evaluate the guards' actions.

The shooting by Blackwater guards that day ignited outrage about the use of private security contractors in war zones and severely strained relations between the United States and the fledgling Iraqi government.

The case remained a sore point during the Bush administration's negotiations with Iraq for an agreement setting new rules for the continuing presence of U.S. troops. Ultimately, a major provision of the agreement ended immunity for private contractors working in Iraq.

U.S. officials restated the government's commitment to pursue justice in the Nisour Square shootings.

Echoing the findings of previous investigations by the Iraqi and U.S. authorities, prosecutors said Monday that they had found no evidence that any of the Iraqis killed had posed a threat to the guards.

Instead, prosecutors accused the guards of acting with blatant disregard for human life and the rule of law.

Some military law specialists said the court of public opinion was likely to weigh as heavily in this case as the legal issues, which is why Ridgeway's testimony - the first time a guard has admitted to crimes while on duty - was so important to the prosecution, and why the venue was so important to the other defendants.

Mark Hulkower, a lawyer for one of the guards, said the lawyers believed Salt Lake City would provide a jury pool "where people are more sympathetic to the experiences of coming under enemy fire."

The five guards charged in the indictment were Paul Slough, 29, of Keller, Texas; Nicholas Slatten, 24, of Sparta, Tennessee; Evan Liberty, 26, of Rochester, New Hampshire; Dustin Heard, 27, of Maryville, Tennessee; and Donald Ball, 26, of West Valley City, Utah.

At a news conference in Washington, the prosecutors said the indictments were the culmination of one of the most complicated investigations in the history of the FBI, involving 10 agents who interviewed hundreds of witnesses during at least four trips to Iraq.

According to the indictments, the Blackwater guards disobeyed orders by leaving their base to respond to reports of a car bomb. Upon arriving at Nisour Square, the indictments said, the guards moved into the circle against the flow of traffic and, without warning, began firing
The shootings were without provocation or justification, said Patrick Rowan, the assistant attorney general for national security. "The consequences were devastating," he said.

Blackwater has not publicly said whether it is paying the legal fees of the guards charged in the case, although a company spokeswoman said last week that Blackwater did cover legal expenses in some instances.