When I was a grad student one of the members of the Kennedy investigation visited our campus. I forget his name, but he worked on the image-enhancement team, and gave an interesting talk about the various extra gunmen that were claimed to be on photos of the "grassy knoll" (among other places).
A few years later (in the mid 80s) I had the pleasure of attending several seminars by Norman Ramsey, who was awarded a Nobel prize soon after. http://en.wikipedia.org/wiki/Norman_Foster_Ramsey,_Jr
He led the acoustics team in the enquiry, and he played us the tape that supposedly showed that there were several more gunshots. One downside of that evidence is that it is the transmission from a stuck mic on a police motorcycle, recorded back at the station. So the tape is basically engine noise. Norman played it and gave visual clues where the gunshots supposedly were. Apart from the noise problem, I recall that it turned out (from commercial radio signals that found their way on the tape) that the supposed shots were at a different time from the actual shots.
At the final meeting Norman recalls overhearing a conversation that went roughly like:
"Hmm, looks like there's no good evidence for a conspiracy."
"Well, that just proves how good a conspiracy it was!"