While I haven't studied the CIA behavior in Mexico as much as I would like, I did stumble upon something which may or may not be well-known. I certainly found it interesting. Here's my train of thought.. I believe the CIA created a file on Lee Henry Oswald long before the assassination. It's theorized that Oswald was impersonated in Mexico shortly before the assassination. I believe the real Oswald was there, and was observed by a mole (or caught on a bug) in the Soviet Embassy, and that a fa