Most civilians and LEO's for that matter don't have enough training to maintain proper trigger control or trigger finger placement when in a high adrenaline life threatening situation. Fine motor skills are gone. I've seen many shotgunners spend hours shooting clays with no problem but take them out in the field and the first pheasant that flies you had better duck because with the excitement of the moment their training goes out the window.
For a defensive sidearm a DA/SA or DAO is a good idea. A long 10 or 12 pound pull gives your brain a chance to catch up to itself.