In your line of work, making a "simple" mistake could get you killed. You already know that. But some mistakes are a lot worse than others. These deadly, "cardinal" sins of officer safety are practically guaranteed to result in bad things happening to you if you commit them.
You are also aware that certain activities that you engage in as a law enforcement officer are more likely by their very nature to expose you to high risks than are some other assignments. Making an arrest, engaging in a traffic contact, and intervening on the scene of domestic mayhem are, statistically, among the most dangerous things you can do. Make an error in your handling of one of these and you should anticipate a really bad day.

