Several years ago, Col. Jeff Cooper came up with four simple gun safety rules that are especially important to the armed citizen. Rule #3 states, “Keep your finger off the trigger until your sights are on the target.” We call that the Golden Rule because it will prevent most negligent discharges.
Years ago, when I first heard of this safety rule, I really thought it would slow me down at a time when being slow might cost me my life, so I began to experiment with the idea and found that such was simply not the case: In the time it takes a shooter to get on target, there is plenty of time to get on the trigger.
Nowadays, most of us who teach defensive shooting carry this rule a step further. We suggest that, until the sights are on the target, the shooter should not even have his finger inside the trigger guard. Instead, the trigger finger should be straight and aligned along the pistol frame as far above the trigger guard as possible. Again, we have found that this does not hinder the ability to quickly address the target. When we get off the target our finger goes straight again.
An actual fight is a dynamic event. There may be a struggle before it is necessary to shoot. One may have to run, one may fall down and have to get up, may have to open doors or close them. Any number of physically active things are possible for the armed citizen to have to deal with. If the person is engaged in these activities while his finger is on the trigger, an unintentional discharge is very possible. In fact, it is highly likely.
I once worked with a police officer who went to the aid of another officer who was being beaten. For whatever reason, my friend had his revolver out and beat the bad guy over the head with it. When he did that his finger engaged the trigger and a shot was fired. The bullet went across the street and hit two innocent bystanders. Fortunately neither one was killed. Adherence to Rule #3 would have prevented that.
It is also important to keep the finger off the trigger and straight while re-holstering. In addition, we never get in a hurry while re-holstering. We make sure that all safeties, if there are any, are engaged and we re-holster slowly.
Rule #3 is an important habit to develop simply because it goes a long way towards preventing negligent discharges and unintentional injuries.