Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

 There is no way, even theoretically, that Jack Ruby fired with his middle finger. It was a revolver, and hot, burning gases come out laterally through the cylinder gap. The first thing they teach you in gun safety class is not to put any part of your hand alongside the cylinder.

What I have is a Smith and Wesson snub-nose 38. Ruby had the Colt Cobra. They are similar, and they both have a lot of recoil. Mine has so much recoil that after shooting at the range, the bottom of my hand is sore.

This guy demonstrates what can happen if you put your finger next to the cylinder.

https://www.youtube.com/watch?v=VFBAcz16GvU&t=71s

So, how can you avoid it when using your middle finger? I guess by flexing your index finger, but this is the result on the right. You think I'm going to shoot a gun like that? I do not have firm control of that weapon. All I have holding the grip are my two weakest fingers, my ring figer and little finger. And my index finger isn't helping at all on the other side. The idea that Jack Ruby would have thought to fire his gun that way is ridiculous. It is patently absurd.

Look: Ruby didn't give any thought to shooting Oswald. He didn't think about doing it at all, let alone think about doing it with his middle finger. He didn't even expect to see Oswald, let alone shoot him. And why should he have, when the Jail Transfer was scheduled for 10 AM.

So, the idea that Jack Ruby plotted to shoot Oswald and decided to do it with his middle finger, because he thought it would look cool, is absolutely ludicrous.

So, why does it appear that way in the Jackson photo? It's because it was a staged photo, and someone had the wrong information. He thought that Ruby had an amputated index finger on his right hand and and would have to use his middle finger. And that's what he told James Bookhout to do. But, in reality, Ruby had an amputated left index finger. He would have had no reason not to use his right index finger.

So, it was a production error, and every movie has them. The guy in the photo masquerading as Ruby was FBI Agent James W. Bookhout.