"Are we just left with conjecture to reach a conclusion on the issue of how Ruby entered the police basement? No, there is evidence, common sense, and Ruby's knowledge of events that prove he entered through the Main Street ramp. ....
"The virtual proof that Ruby came down the Main Street ramp is that within a half hour of his arrest, and right after he was taken from the basement to the jail on the fifth floor (which was long BEFORE [DPD officers] Pierce, Putnam, Vaughn, and Maxey had been interviewed and given their statements), Ruby told Dallas police detective Barnard Clardy and other detectives that he had entered through the Main Street ramp and had seen Pierce driving out of the ramp.
"How could Ruby possibly have known this if he hadn't, in fact, been at the entrance to the Main Street ramp? I mean, Pierce himself didn't even receive instructions to drive out of the Main Street ramp until around 11:15 a.m., just six minutes before Ruby shot Oswald." -- Vincent Bugliosi; Pages 108-109 of "Reclaiming History" (Endnotes)
