Perry meets with Helen in her apartment wearing a light colored overcoat. When he arrives back at his office he is wearing a dark black overcoat.
When Joyce first sits at the bar, she is seen unclasping her purse & reaching in to pull out a cigarette. The next moment when the bartender approaches her she is seen already taking a drag off a smoking cigarette. She didn't have time to light it.
Robert Crane (Denver Pyle), his sister Helen Reed (Constance Ford), Perry Mason (Raymond Burr) and Della Street (Barbara Hale) are in Perry's office sitting around Perry's desk. The first scene has two small stacks of paper in front of Perry and he has his arms across the stacks. The next scene has only one stack. Then both stacks of paper are in front of Perry.
There is a knock at the door leading from Perry's private office to the outside corridor. Perry asks Della to open it, saying it must be Paul. But Paul has a special knock, not one used by the caller; Perry should not have been surprised when the caller turned out to be Lt. Tragg.
When Lt. Tragg finds the gun inside Joyce Martell's purse in the murder room, he picks it up barehanded by the handle instead of using a pen or pencil in the barrel. Because it's possibly the murder weapon, he would not have added his fingerprints to those already on the gun.