The top federal prosecutor in South Dakota agrees to reexamine dozens of unsolved homicides, venturing into a long-running feud between the Oglala Lakota Nation and the FBI. PINE RIDGE INDIAN RESERVATION, S.D. — The top federal prosecutor in South Dakota, stepping into the middle of a bitter dispute between the Oglala Lakota Nation and the FBI, has reopened a series of unsolved murder cases that tribal leaders say the FBI has for too long ignored.