The problem with the HSCA report is that is says there was probably a conspiracy but couldn't give the actual evidence of it or say who was involved with Oswald (as they did say that Oswald had fired three shots from behind).
No, they did provide evidence, quite a bit of evidence: the DPD dictabelt, the post-assassination box movement in the sniper's nest, Ruby's Mafia ties, Ruby's route to entering the DPD basement, the parallels between Oswald's execution by Ruby and the Mafia's execution of hired gunmen, the witness accounts of hearing shots from the grassy knoll, relevant anti-Castro Cuban activity, etc., etc.
You can't say there was a conspiracy and then not say who or what the conspiracy was. That doesn't make any sense.
But that's not what they said. Even the final report clearly identified Mafia elements and anti-Castro Cuban elements as plausible suspects. But Blakey and other HSCA personnel noted that the committee had reached the end of its lifespan and thus could not continue its investigation. A key factor was that the acoustical evidence was only firmly developed toward the end of the committee's lifespan.
