Qui tam cases from Iraq are investigated by an F.B.I. unit in Rock Island, Illinois. According to Grayson, the unit has a "standing order" to get approval from the attorneys at Vinson & Elkins before questioning anyone at Halliburton or KBR. "F.B.I. agents are not supposed to politely ask permission," he says. "The most common interview technique by the F.B.I. is a knock on your door at nine o'clock at night. They're not allowed to do that when it comes to Halliburton and KBR employees."
