We used to oversimplify and consider that an officer could not be held personally liable unless he had committed a "feasance" violation. These are:
Non-feasance, you didn't do what you should have known (by your training and experience) needed to be done.
Mal-feasance, you did the right thing, but you did it badly or wrong, as you should have known as above.
Mis-feasance, you did the wrong thing, also as above