First, films ave never been known for accurately portraying anything. Makes no difference whether you are talking technology, police or military tactics or????

Until at least the mid-late 1950s there was very little training of police officers. They were literally hired, handed a badge, gun, and call-box key and told to go to work. Were they taught to cock a revolver under the described circumstances, no. They weren't taught not to either! Did some officers do it this way, undoubtedly yes. Should they have, obviously from modern tactical perspective they shouldn't have, but that was a different time and things were different.

tocohillsguy says "Never in my 22 years of law enforcement was this trained." Don't know when that was, but when I was hired, in 1969, there were still officers on the department that had been on the street since the 1930s. It was really interesting to talk about their early days and how things had been "Back then", and what I have related is based on discussions I have had with "The old heads" while they were still around.