When the inspector, Hopkins, and Pettijohn are looking at the wardrobe of the murdered man, in the closeup, Hopkins has his arms crossed. In the long shots, his arms are down by his side.
When Rita Warren (Brenda Marshall) is practicing her strip routine in front of the mirror, she drops a shoulder wrap to the floor. After the butler comes in, the the wrap is gone in the long shots.
On the label for the Novocain at the dentist's office, epinephrine is misspelled 'epinephin'.
The tap water Pettijohn uses to replace the "anesthetic" would be difficult to tolerate being injected, especially into the gums. Since this was freshwater (not saline) and would have a different ph than the human body, it would burn quite a bit after being injected. And while tap water is safe to drink, it's not safe to inject.
The shadow of the boom mike is visible when Francis and his wife are in front of their closet when he tries to get her to leave before the police arrive.