The CIA had involvement, simply no doubt. Their involvement would not necessarily reveal sources and methods. It would reveal how they were doing stuff they would be embarrassed about and how they most likely screwed it up.
Yeah, but (ex CIA agent) William F. Buckley once said "you could tell it was a CIA operation because everyone in the room was killed, except the target."
I believe that line was in one of his Blackford Oakes stories.
Certainly, the CIA and FBI knew Oswald and were monitoring him on an occasional basis. A former Marine does not move to Russia, marry a Russian woman and live there for a year without their keeping tabs on the guy.
Oswald had more than one connection with CIA assets: Clay Shaw in New Orleans and George De Morenscheilds (sp?) in Dallas. The CIA also knew he went to the Russian Embassy in Mexico City and had pictures of him there that their people took.
Oswald kills JFK. When the CIA connection is made the CIA knew they would be called on the carpet. That was when the CIA went full out to make sure Oswald was to be charged as a lone gunman. Their invovlment was to protect themselves to avoid any blame.