Criminal defense lawyers and their investigators routinely venture into rough neighborhoods to interview witnesses and gather evidence. But there’s probably little concern about sniper attacks, mortar fire and roadside bombs.

Those are the fears of a group of private defense lawyers who want to travel to Iraq to conduct their own investigation amid the prosecution of five Blackwater Worldwide security guards, charged with voluntary manslaughter in the killing of 17 unarmed Iraqi civilians in a shootout in 2007.