During a lifetime of developing and teaching defensive pistol techniques, Col. Jeff Cooper condensed all of the firearms safety rules into just four simple statements that anyone could learn and memorize. Rule Number 3 simply states, "Keep your finger off of the trigger until your sights are on the target."
I went into police work when the double-action revolver was still king. And the shooting technique we all learned was that at the same time your hand gripped the revolver, your finger was on the trigger. I frankly don't recall hearing about all that many negligent discharges resulting from this practice and suspect that the long trigger pull of the DA revolver was what kept more of these incidents from occurring.
Eventually, I began carrying a 1911 pistol almost exclusively and finally got around to taking the 250 pistol class at Gunsite. Now, I will tell you that the instructors at Gunsite are serious about Rule 3. In fact, they teach, as do most other good defensive schools, the trigger finger should be completely out of the trigger guard until the sights go on target. Frankly, I still didn't think it was all that big a deal, but I was playing in their back yard and decided I would follow their rules. As I became personal friends with many of those instructors, I was privy to the various horror stories about what happened when Rule 3 was violated. These stories, I might add, always involved a loud noise and very often a good bit of blood.
Then came the day when I was an assistant instructor at a class on the West Coast. One of our students was a retired deputy sheriff—an old revolver guy—who was taking the class with his 9 mm Glock. I had cautioned him twice about his trigger finger and was considering taking him off of the line if he couldn't get with the program. That was when he went to re-holster one more time. Yep, there was a loud noise. There were holes in the leg of his khaki pants. And, when I got him to the shooting shed and he dropped his trousers, he had plowed a nice gouge in his thigh. Simply put, adherence to Rule Number 3 will avoid the vast majority of negligent discharges that might occur.
What follows is one of my favorite quotes from Colonel Jeff Cooper. I have cleaned it up just a bit so as not to offend delicate sensibilities.