THE WHO, WHAT, WHY, WHEN AND WHERE OF TASER USE

What it is The Toronto Police Service owns 550 X26 Tasers. Chief Mark Saunders recently requested $1,319,300 from the police board to replace the weapons, which he says are out of date, with a newer model.

How it works When the weapon is fully deployed, nitrogen propellant launches a pair of barbed darts at a suspect. The darts are connected to the weapon by wiring, which delivers electricity into a suspect, overriding the neuromuscular system and usually causing the person to collapse.

Drive stun The weapon can also be held directly against a suspect’s body to deliver a shock.

Why doesn’t it kill you? The Taser’s “peak open circuit arcing voltage” is 50,000 volts, Thomas Braidwood wrote in a report following the death of Robert Dziekanski after he was Tasered in the Vancouver airport. When the weapon is pressed against someone’s body, the X26 voltage drops to 1,300 volts.

The risk The danger is that the rapid pulses of electricity generated by the Taser will overtake the heart’s natural beat, leading to a “chaotic, unco-ordinated” rhythm and no blood pumping, according to Zian Tseng, an associate professor at UC San Francisco.

Who’s at risk? Women, children, and anyone who is very thin, according to Tseng. These people could have less distance between the surface of their skin and their heart.

Where police should aim In short, anywhere but the heart, according to John G. Webster, professor emeritus at University of Wisconsin-Madison. “You don’t want to shoot for the eyes. But the shoulders would be good,” Webster said.