The HSCA concluded that there was the [high?] probability of a shot from the GK area when the JFK limo passed, and that there had been a JFK assassination conspiracy.

Upon what lame evidence or lame analysis did it base its lame conclusion?

I watched it when if first played on American TV, hosted by Geraldo Rivera. It played over several nights if I remember right and I'm not sure I caught all of it, but what I saw was very good. I'll check out the YouTube video.

It was the cable channel Showtime. Over 2 nights.
Hosted by Edwin Newman. I watched it.

https://time.com/archive/6707829/video-what-if-oswald-had-stood-trial/

Is it the guy I've circled in yellow?

    Yes, that guy wearing a HAT inside the Yellow Circle has ALWAYS been accepted as being Wiegman. Yet, No eyewitness has ever said they saw Wiegman in this position on the Bell Film and this includes Wiegman himself.

I just noticed Walt Cakebread posted in this thread. That's a name I hadn't heard in eons.

I had a back-and-forth (if we can call it that) with Walt Cakebread where he said that LBJ was going to announce that Castro was behind the assassination. But the Soviets had learned about the conference and had launched their nuclear armed bombers to the US to attack us. They were on their way, loaded with thermonuclear weapons that they were going to drop on us. So LBJ canceled the announcement to prevent the attack.

I, let us say, strongly disagreed with his claim. As in, there is no damned record anywhere of such acts. By LBJ, by the Soviets. It simply didn't happen. It's all made up. He insisted otherwise. It was at that point where I said to myself, "You dummy, you are trying to reason with a deranged person."

Not all JFK conspiracists are psychotic. But I will wager that all psychotic people are JFK conspiracists. See above.

i scheduled Executive Action to record on TCM about a week ago. Although that movie and Oliver Stone's JFK are both fictional accounts of the JFKA, I though Executive Action was the better movie. The movie JFK was ruined by the choice of the lead actor. Nothing against Kevin Costner, but he was a poor choice to play Garrison. He wasn't right physically for the part and it wasn't one of his better performances. If I had cast the movie, I would have chosen G. D. Spradlin. He would have a little old for the part but I think he could have pulled it off. For most of his career, he was older than the characters he played.