What evidence is there for us to consider regarding this question? If we accept the premise that the driver, SSA Bill Greer stopped the limo during the attack, was that an accident? Was he momentarily startled to such an extent that he was uncertain what to do or which way to go? Was it an intentional act as part of a concerted action to assure that the president would not escape execution? Or, is it demonstrably true that while the presidential limousine did actually slow down during the attack, the claim that it came to a complete stop is false?
Chapter 4, The Limo Stop examines these questions.
