Ken Curtis, in the part of Tim Durant, lapses into somewhat of an Old West accent and speech pattern (that he would employ for years in his role as Festus), when Mason interviews him about what he saw during the crime. All other times Durant is on screen, he speaks in a much more refined manner.
Lt. Tragg is witness to a homicide because he is investigating an attempted homicide perpetrated in the same whereabouts earlier that day. Police departments don't assign homicide investigators to attempted homicide cases.
A pistol shot from that distance from under a blanket would be next to impossible.
Judd Curtis, who's part owner of the circus, lights up a cigarette inside the main tent while the show is going on. But circuses don't allow smoking in the tent because of all the sawdust, straw and other flammable materials there. (Paul and Perry also had cigarettes in their mouths but didn't light them because the clown pointed his gun at them as if he would shoot the cigarettes out of their mouths.)
Two people standing a few feet away from the murderer fail to hear the report from his murder weapon, a .357 Magnum revolver.