Here is a summary of Heim, et al., 2006:
Hum Factors. 2006 Fall;48(3):413-21.
The risk of involuntary firearms discharge.
Heim C1, Schmidtbleicher D, Niebergall E.
Author information
1Johann Wolfgang Goethe-Universität Frankfurt, Institute of Sports Science, Frankfurt, Germany.
c.heim@sport.uni-frankfurt.de
Abstract
OBJECTIVES:
To investigate whether unintended muscle activity induced by motor overflow can result in the unintentional discharge of a firearm.
BACKGROUND:
In the past few years an increasing number of people have been injured, sometimes fatally, as a result of police weapons being discharged involuntarily.
METHODS:
Two experiments were performed using a pistol fitted with sensors to register the pressure exerted on the hand stock and the trigger. In Study 1, 34 police officers reacted to a set case using the prepared pistol. In Study 2, 25 participants performed 13 tasks requiring the use of different limbs.
RESULTS:
In Study 1, about 20% of participating officers made contact with the trigger, thus violating police regulations to keep the trigger finger outside the trigger guard at all times until a conscious decision to fire has been made. Study 2 showed that motor activity in different limbs leads to a significant increase in grip force exerted on a firearm (significant results for 12 of 13 trials, Bonferroni-corrected p < .004). Furthermore, pressure on the trigger resulting from involuntary muscle contractions was, in certain cases, sufficient to unintentionally discharge a weapon.
CONCLUSION:
Unintentional discharges attributable to involuntary muscle activity can be a real danger for police officers when carrying out their duties.
APPLICATION:
Results may help improve police training with the aim of reducing the danger of involuntary discharges in real-life situations.
*****
Science tells us that Deaf Smith could be a trigger toucher and not even know it.
44 AMP,
Professional civilian training is aimed at what is best for you, in a defense situation. Military training is aimed at what is best for the military, in every situation.
Where does the necessity of a manual safety come in when your follow the military "empty chamber" rule? It does not.
And yet, the military demanded a manual safety on the 1911.
Perhaps, because, even back then, they recognized that no matter how you train people, a significant percentage are going to do what they think is best for them at the time, OR they are going to unconsciously violate their training. Either way, no training is going to cover 100% of the people, 100% of the time.
The Army's specification for a .45 Auto pistol required a safety, and the Colt M1905, their initial submission, had the grip safety. The Army conducted extensive field trials with the prototypes, and some refined prototypes were built and tested. It wasn't until the M1910 that the Army told Colt and Browning to add the thumb safety lock. Some M1910s were fitted with the required safety lock, and the resulting pistol, with a few additional minor changes, became the M1911.
The reason the Army wanted the thumb safety was so cavalry could safely reholster while on a galloping horse. While one can safely reholster with just a grip safety, doing so requires fine motor skills that are likely unavailable when atop a spirited steed. Activating a thumb safety is much safer.