Although I was a veteran (USARV, 1971) I had no combat experience when I was able to get a job in policing at the end of 1973... I was almost five years on the job when I ended up firing the only shot in a 22 year career.... then spent a few months in and out of court as the judge decided whether I was justified or not.... Since I had a country background I was comfortable with shotguns from the beginning - but not very well trained at all (very minimal shotgun training in the academy and barely trained enough to qualify every few years...) about basic shotgun tactics I was pretty clueless - and all things considered lucky that one day...
That single incident caused me to do a lot of thinking and I went out of my way from that day forward to learn as much about my chosen weapon (far as I'm concerned a pistol is what you use because a shotgun wasn't available, period....). I never again fired a single shot on the street - and all these years later and long retired - I hope it stays that way. What I did learn is that most aren't very comfortable with shotguns for defense unless they're hunters or have had decent training in the skills and tactics needed to be successful. Many, many have shotguns but rarely ever use them - certainly not ones designed specifically for that one time - when it's all on the line. That's why I speak up every now and then about what's actually needed - and magnum rounds that will stop anything living aren't exactly anything other than something to brag about. What is needed are the basic rounds (2 3/4" nine pellet 12 ga. 00buck or rifled slugs - your choice), a solid understanding of their limitations, and enough actual use that you're fully comfortable with your gun in most circumstances...
All of the above is why, when I first came to this site... I found Dave McCracken's writings on the topic so valuable. Hope any young man or woman who gets into policing where shotguns are issued as part of the daily gear - have the opportunity to read what he's written on the subject...