WASHINGTON — A federal jury on Wednesday convicted four Blackwater Worldwide guards in the fatal shooting of 14 unarmed Iraqis, seven years after the American security contractors fired machine guns and grenades into a Baghdad traffic circle in one of the most ignominious chapters of the Iraq war.
The guilty verdicts on murder, manslaughter, and gun charges marked a sweeping victory for prosecutors, who argued in an 11-week trial that the defendants fired recklessly and out of control in a botched security operation after one of them falsely claimed to believe the driver of an approaching vehicle was a car bomber. Jurors rejected the guards’ claims that they were acting in self-defense and were the target of incoming AK-47 gunfire.
Overall, the defendants were charged with the deaths of 14 Iraqis and the wounding of 17 others at Baghdad’s Nisour Square shortly after noon on Sept. 16, 2007. None of the victims was an insurgent.
‘‘This verdict is a resounding affirmation of the commitment of the American people to the rule of law, even in times of war,’’ said Ronald Machen Jr., US attorney for the District of Columbia, whose office prosecuted the case. ‘‘I pray that this verdict will bring some sense of comfort to the survivors of that massacre.’’
Defense attorneys appeared stunned and said they would appeal. David Schertler, an attorney for Dustin Heard, called the result ‘‘incomprehensible.’’
‘‘The verdict is wrong,’’ Schertler said. ‘‘We’re devastated. We’re going to fight this every step of the way.’’
The jury of eight women and four men deliberated 28 days before convicting Nicholas Slatten, 30, of Sparta, Tenn., of murder. Also convicted were Paul Slough, 35, of Keller, Texas, of 13 counts of manslaughter and 17 counts of attempted manslaughter; Evan Liberty, 32, of Rochester, N.H., of eight counts of manslaughter and 12 counts of attempted manslaughter; and Heard, 33, of Knoxville, Tenn., of six counts of manslaughter and 11 counts of attempted manslaughter.
Jurors also convicted Slough, Liberty, and Heard of using military firearms while committing a felony. Prosecutors dropped three counts against Heard after jurors deadlocked on them.
Slatten faces a mandatory sentence of life in prison for murder. The other three — who, like Slatten, are military veterans — face a mandatory minimum sentence of 30 years in prison.
US District Judge Royce Lamberth ordered the men held pending sentencing. Jurors declined to comment.
The outcome capped a difficult, yearslong quest by prosecutors to bring the case to trial and a milestone in the government’s efforts to monitor security contractors’ conduct on the battlefield.
The contractor shootings and the American government’s refusal to allow the men to be tried in Iraq sent relations between the two countries into a crisis, and the Blackwater name became shorthand for unaccountable US power.
In Congress, lawmakers denounced the Blackwater shootings as recently as this summer, but legislation that would provide clearer jurisdiction to prosecute criminal wrongdoing overseas by private contractors has languished for years.
The author of the proposed change, Senate Judiciary Committee chairman Patrick Leahy, a Vermont Democrat, applauded the verdict but added, ‘‘It should not have taken this long for justice to be served. . . . Ensuring that our government has the ability to hold government contractors accountable should be a bipartisan issue, and I hope senators of both parties will work together to pass this important reform.’’
Prosecutors called 71 witnesses to four for the defense, including victims, surviving relatives, and nine fellow Blackwater guards. The 30 Iraqis who testified represented the largest number of foreign witnesses to travel to the United States for a criminal trial, prosecutors said.
At the time of the shootings, the defendants were among 19 Blackwater guards providing security for State Department officials in Iraq. Their convoy, called Raven 23, was clearing a path back to the nearby Green Zone for another Blackwater team evacuating a US official from a nearby car bombing.
Defendants’ attorneys said their clients acted reasonably at a time when the Iraqi capital was the scene of ‘‘horrific threats’’ from car bombs, ambushes, and attacks, sometimes aided by Iraqi security forces infiltrated by guerrillas.
During the trial, under cross-examination, some ex-Blackwater employees differed over whether Slatten or others fired the first shots, and some agreed that they heard incoming AK-47 fire.