Seven years after American security contractors killed 14 unarmed Iraqis by firing machine guns and grenades into a Baghdad traffic circle, a jury…convicted all four Blackwater Worldwide guards charged in the incident…The guilty verdicts marked a sweeping victory for prosecutors, who argued in a 10-week trial that the defendants fired wildly and out-of-control…after one of them falsely claimed to believe the driver of an approaching vehicle was a car bomber. The guards claimed they acted in self-defense and responded appropriately…, their defense said. Overall, 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. David Schertler, who represents one of the guards, Dustin Heard, called the verdict “incomprehensible.”