Shooting through a door is usually a bad idea. Your ability to see the target is often obscured or nonexistent, and it may be difficult to show that you believed that you were confronting a deadly threat.  Shooting through an inside door may be less problematic than one that is an entrance to a building that you are defending. Interior doors are usually of flimsy construction. A person who has retreated to a bedroom or bathroom and who has locked the door may have less options than someone who is defending an entrance door.  If someone has already...