#1 If you believe in a conspiracy then you believe that Ruth Payne was involved. She had to be since she was Oswald's connection to get a job at the Book Depository. You also must believe that Roy Truly, the man who hired Oswald there, was involved. In 50 years there has never been any evidence that either has had any connections to the FBI, CIA, mafia, or any other group conspiracy theorists point the finger at.

#2 You also have to believe that Jack Ruby, running late as it is, decided to risk missing Oswald all together when he stopped off at Western Union to wire one of his employee $25 to pay her rent like 3 minutes before he shot Oswald. You'd also have to believe that Oswald himself was involved in his own end as the only reason he hadn't been transported long before Ruby arrived at the police station was because he asked for a change of clothes.

#3 The physical evidence overwhelmingly shows that all shots came from the 6th floor of the book depository. The infamous "magic bullet" presupposes that Kennedy and Connelly were seated on a level plane, but in reality we know that model Lincoln had a front seat that was sunken around 13 inches below the rear seat. When corrected the trajectory shows Lee Harvey Oswald was the only one who could have fired that shot.

Oswald acted alone.