FORTY-FOUR years ago today, a clothing company owner named Abraham Zapruder filmed the assassination of John F. Kennedy in Dallas. And for 44 years, most people have presumed that his home movie captured the assassination in its entirety. This presumption has led to deep misunderstandings.< > But what if Zapruder simply hadn’t turned on his camera in time?< >If the commission had followed up this insight, it would have conceivably been able to describe the duration and intervals of the shooting sequence: that Oswald fired three shots in approximately 11.2 seconds, with intervals of 6.3 seconds and 4.9 seconds between...