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

In the movie, The Left Hand of God, Humphrey Bogart has to determine which of three men fired the shot that killed a priest, so one by one, he sniffs the muzzle of each of their rifles. He quickly determines that the man in the middle fired the shot. 

So, why didn't Dallas Police report sniffing the muzzle of the 6th floor rifle and that of Oswald's revolver to determine if either had been recently fired? Wasn't the sniff test used in those days? 

And why didn't they report finding shooting residue inside Oswald's revolver? Shouldn't there have been some soot if he had recently fired it several times? Here is a picture of a dirty cylinder.

  Here is another one with a heavier layer of soot.

So, what did they see when they opened Oswald's revolver?

There is nothing definitive about that, but that doesn't look to me like a dirty cylinder. It certainly doesn't jump out at you that it is a dirty cylinder. And don't you think that the detective holding it and examining it would be able to see signs of discharge? So, is there a Dallas Police report observing signs of gunshot residue inside Oswald's revolver? If not, why not?