Binnie - Giancana was appearing before a federal grand jury. He was scheduled for a fifth appearance when he was murdered. However, newspaper reports stated that he WAS, or had been, subpoena to appear before a congressional committee. Either he would be subpoenaed or the transcripts would be subpoenaed. The lawyers would have to battle it out. Apparently his immunity plea would require him to testify when necessary ( I'm not sure how this worked). What if Giancana appeared before a congressional committee and took the 5 th? He had immunity. As I said, something must have been worked-out requiring him to testify. I imagine the issue would have benn settled in court.

Here's another one. Why was Trafficante not granted immunity to testify? He appeared before The Congressional Committee On Assassinations ( or some committee) and pleaded the 5th on most questions. I've never understood why he wasn't offered immunity.

Roselli had been talking to the Feds since the early 70's. Some of his testimony resulted in a grand jury appearance for Accardo. As you might expect, this did not go over well. Accardo was overheard saying he would not forget what Roselli did.

But the most common theory is that Trafficante had Roselli killed. After Roselli and Giancana were eliminated, the only person left that was involved with the Castro deal was Trafficante. Kinda looks strange, but nothing has ever been proven relative to the govt's involvement in the deaths of these guys.