Why do some people feel that Lee Harvey Oswald had links to either American or Soviet intelligence?

Why did Oswald defect to the Soviet Union? Why did he not follow through on Soviet citizenship? What made him decide to return to the United States?

Most people who met Oswald concluded that he was mentally unstable. What evidence is there of this?

What evidence is there of Oswald impostors? Why is this important?

What role did conspiracy buffs say Jack Ruby played in the conspiracy? Is this viable?

What was the range and scope of the Warren commission's investigation? Why did it not put an end to the conspiracy theories?

What was the nature of the investigation of Jim Garrison?