Designed as an alternative to firearms, Tasers are marketed as a “less lethal” device and used by over 16,000 police forces in 107 countries. A new review assessing the health risks of these weapons determines the most dangerous risk is head injury from an uncontrollable fall, which can lead to death, though other harms, including ventricular fibrillation, may occur.

“Tasers have been shown to produce a short lived decline in cognitive function, which resolves within an hour,” wrote Owen Dyer, author of the review and a freelance journalist based in Montreal.

Global Weapon

Worldwide, police officers have used "stun guns" roughly 1.35 million times, more often during training (700,000 times) than during actual arrests (650,000), Dyer notes.

A Taser is shaped like a pistol and uses compressed nitrogen to fire two barbed electrical probes that deliver a pulsed 50,000 volt shock. This causes skeletal muscle contractions and pain. Some models of the weapon also have "drive-stun" mode, where the shock is delivered directly to the body. This causes pain but not muscle contractions.

"Our [TASER CEW battery] incapacitates threatening subjects via an electrical charge that specifically targets the motor nerves that control movement," notes the company website.

According to Dyer, health risks from being tased include eye injuries, seizures in people with epilepsy, tonic-clonic (grand mal) seizures in healthy people, collapsed lung, skin burns, and muscle, joint, and tendon injuries.

The most dangerous risk is fatal head injury following a fall.

What about the heart?

Questioning the neutrality of existing research sponsored by Taser International of Arizona, Dyer references instead a major dispute surrounding the weapon's potential to induce lasting arrhythmias. When testing a next generation replacement for the X26 (the most commonly used model), the prototype apparently induced a lasting arrhythmia. Following redesign, this effect disappeared in subsequent tests.

According to Dyer, one separate study of eight cases concluded tasing had caused ventricular fibrillation (v-fib), where the lower chambers of the heart quiver and the organ can’t pump any blood resulting in cardiac arrest. Although no product tests have produced a similar v-fib, volunteers did not include people with heart disease or alcohol problems or drug problems — or the rapid heart rates occurring during an actual confrontation with the police.

Notably, Darryl Turner, 17, died shortly after he was tased by police. In 2008, Turner had been arguing with his boss at a Food Lion in Charlotte, N.C. where he worked. Police were called and after continued argument, an officer fired his Taser twice at Turner's chest, holding the trigger for 37 seconds and then for 5. An autopsy found the shock sent Turner into cardiac arrest.

The company was found negligent for failing to warn officers of the dangers of discharging into the chest and giving lengthy shocks.

Source: Dyer O. Tasers. BMJ. 2015.