At least three Iraqis appeared yesterday before a federal grand jury hearing evidence in the September shootings in Baghdad by Blackwater Worldwide security guards that left 17 Iraqis dead. After an FBI investigation last year, federal prosecutors have been seeking to determine whether the contractors, who are immune from Iraqi law under a 2003 U.S. occupation decree, can be charged with any crime in the United States. The Iraqi government alleged that the Sept. 16 shootings in Baghdad's Nissor Square were an unprovoked attack on civilians. [also refers to Dyncorp, Triple Canopy]