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SHOCKING: The next generation of TASER—the eXtended Range Electronic Projectile (XREP)—is being designed to fire wireless probes as far as 65 feet from a half-ounce (14–gram) cartridge.
Courtesy of TASER International, Inc.

The recent deaths of three men in Canada after police stopped them in their tracks with TASER guns have resurrected the debate over use of the weapons, which utilize electric pulses and strong muscle contractions to incapacitate people considered to be a threat to officers and the public.

The three separate cases are still under investigation, but the association between them and the technology has led to misconceptions about the way these weapons affect the body, law enforcement and TASER International say.

TASERs, which represent the lion's share of all electronic-control devices used by law enforcement, work by shooting two metal probes that release electricity into the body, causing neuromuscular incapacitation. Generally, the victim feels as though "he is in a full-body charley horse," but does not lose consciousness, says Steven Ashley, a former deputy sheriff in Livingston County, Mich., who retired from the force in 1989 and is now a law enforcement consultant. "They short-circuit the electrical signals in the body."

The deaths in Canada, however, have some local politicians calling for a review of how the weapons are used, and some health care officials say these weapons are not nearly as benign as portrayed. A report released earlier this year by the Heart Rhythm Society, a Washington, D.C., organization of cardiac arrhythmia doctors and patients, found that electronic-control devices like the TASER may trigger "significant arrhythmias" in patients with pacemakers.

But Ashley, a senior master instructor for Scottsdale, Ariz.–based TASER International and an instructor for its competitor, Stinger Systems, Inc., in Tampa, Fla., disagrees that TASER weapons damage the heart or other internal organs. "The energy they emit follows the grain of the muscles and impacts sensory motion and the motor control," he says. "It doesn't go off searching for internal organs." The most common lingering effect after the muscle contractions, he says, is muscle fatigue lasting a few hours. But, he admits, "you don't know exactly how each individual will react." Other variables determining victims' injuries are how hard they fall and where they land.

TASERs contain two probes, each with a half-inch metal tip roughly the size of a fishhook that is designed to latch onto a target's body and / or clothes. The probes are packed into cartridges and are propelled at their target using compressed nitrogen. The probes travel at 180 feet (55 meters) per second when fired, spread one foot (30 centimeters) apart for every seven feet (2.1 meters) they travel and must land at least four inches (10 centimeters) from one another on the intended target to complete the circuit and channel an electric pulse into his or her body. If the probes are less than four inches apart, the TASER will deliver a shock, but not incapacitate the person.

A TASER uses up to 50,000 volts of arcing voltage to deliver a charge via the tips of its probes. Ashley, however, says TASERs are typically programmed to fire for five seconds, not enough time for a full discharge—the cycle can be stopped in less than five seconds if the weapon's safety lever is moved into the "safe" position. The high voltage is available so that a TASER's charge can reach across a gap of about two inches (or five centimeters) of air or clothing to connect with the victim's body; the probes do not have to actually penetrate skin to work. When fired, the TASER X26 weapon, a model commonly used by law enforcement, operates at 19 pulses per second at a pulse duration of 100 microseconds to deliver an average current of 2.1 milliamps. (Editor's note: in an earlier version of this story, it was mistakenly reported that a TASER has a peak current of 3 amps.) Put in perspective, a University of Illinois at Urbana-Champaign study indicates that at 20 milliamps, breathing becomes labored. At 100 milliamps, ventricular fibrillation of the heart—an uncoordinated twitching of the walls of the heart's ventricle—occurs.