When Perry is in Jonathan Hyett's office discussing the return of the money to the bonding company with him, Hyett is leaning forward on his elbows during his frontal shots and leaning back in his chair during his back shots (likely to provide a better frontal shot of Raymond Burr).
When Perry and Paul enter an apartment, Paul turns on the room light. The click of the light switch is heard about a half second before the light come on.
As Mr Hyett (senior) places the gun in the "dead" Mr Brewster's right hand, Brewster's fingers clearly flex and move in taking hold of it.
When Jonathan Hyett is on the stand and testifies that he tampered with the crime scene, he is not advised of his rights against self-incrimination. He is not represented by counsel, and in other episodes when witnesses are about to testify regarding a crime they committed (except, of course, the murder that's the subject of the case at hand) the judge or one of the attorneys will advise them of their Fifth Amendment rights.
When Perry hands Mrs. Ellis the order from Barton's in San Francisco, he doesn't first enter it into evidence, or show it to the judge, or Mr. Burger. No document is ever presented to a witness to be read without first being entered as evidence, and looked at by the judge and the other party.