The single-bullet theory, often derided and discredited by referring to it as the magic-bullet theory, was introduced by the Warren Commission in its investigation of the assassination of U.S. President John F. Kennedy to explain what happened to the bullet that struck Kennedy in the back and exited through his throat. Given the lack of damage to the presidential limousine consistent with it having been struck by a high-velocity bullet, and the fact that Texas Governor John Connally was wounded and was seated on a jumper seat in front of and slightly to the left of the president, the Commission concluded they were likely struck by the same bullet. Generally credited to Warren Commission staffer Arlen Specter (later a United States Senator from Pennsylvania), this theory posits that a single bullet, known as "Warren Commission Exhibit 399" or "CE 399", caused all the wounds to the governor and the non-fatal wounds to the president, which totals up to seven entry/exit wounds in both men. The theory says that a three-centimeter-long (1.2") copper-jacketed lead-core bullet from a 6.5×52mm Mannlicher–Carcano rifle fired from the sixth floor of the Texas School Book Depository passed through President Kennedy's neck into Governor Connally's chest, went through his right wrist, and embedded itself in Connally's left thigh. If so, this bullet traversed a back brace, 15 layers of clothing, seven layers of skin, and approximately of muscle tissue, and pulverized of Connally's rib, and shattered his radius bone. The bullet was found on a gurney in the corridor at Parkland Memorial Hospital after the assassination. The Warren Commission found that this gurney was the one that had carried Governor Connally. In its final conclusion, the Warren Commission reportedly found "persuasive evidence from the experts" that a single bullet caused President Kennedy's neck wound, and all of the wounds found in Governor Connally. It acknowledged that there was a "difference of opinion" among members of the Commission "as to this probability", but stated that the theory was not essential to its conclusions and that all members had no doubt that all shots were fired from the sixth-floor window of the Depository building. Most pro- and anti-conspiracy theorists believe that the single-bullet theory is essential to the Warren Commission's conclusion that Lee Harvey Oswald acted alone. The reason for this is timing: if, as the Warren Commission found, President Kennedy was wounded some time between frames 210 and