The risk of involuntary firearms discharge.

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.