The following information on left handed and off-handed shooting of handguns comes from Section 52 of Shooting by J. Henry FitzGerald. Shooting is also available to purchase in print.
Every officer should practice shooting with right and left hand and should carry his revolver where he can get it with either hand. You never know what your favorite gun hand will be doing when you decide to draw your revolver. A few hours of practice with either hand may net you big results. You use both hands to subdue a prisoner who is unarmed. This is not as important as being able to use either hand when your life is in danger. A bullet through your right arm or shoulder and you are at the mercy of your assailant unless you can use your left hand. You may be leading a prisoner with your right hand and his friends interfere; if you release him while you reach for your revolver valuable time is lost and you may lose your man.
It is not the idea of this book to teach officers to use their revolvers unless absolutely necessary. The officer who knows his revolver and knows how to handle it knows to a fraction of a second how long it will take him to get into action and is not liable to make a mistake as one who is not familiar with firearms.
I have stated many times that if an officer who has never fired a shot (and there are several of them) will stand fifteen feet from a silhouette target and do as he is told for five minutes, he can then fire three shots with right hand and three shots with left hand and all will hit the target at a speed of about nine seconds. In future trials he will hit the target and decrease the time until it is between three and four seconds. Who cares to argue with a man who can, with either hand, hit you six times in three seconds? I’ll bite; who does?
Many police departments are at the present time practicing with right and left hand. The six hundred New York State Troopers are all two-hand men. Buffalo and many other departments have used both hands in their shooting course, and all are benefited thereby. Even officers who are fair shots with the right hand will, on the first trial with right and left hand, make just as good a score with one hand as the other on the silhouette target.
New Jersey State Police qualify with right and left hand on their adopted shooting course.