Police departments in Chicago and the suburbs have embraced the Taser, a device marketed as a tool to reduce shootings by officers.
The weapons' manufacturer contends that if officers can use electric shocks to prevent dangerous situations from escalating, police might shoot their guns less.
But that hasn't happened in Chicago.
In 2010, the city armed hundreds more officers with the weapon, fueling a 329 percent jump in Taser use, from 195 incidents in 2009 to 836 in 2011. Yet shootings by police didn't drop significantly during that period, according to figures from the city's Independent Police Review Authority.
The numbers raise questions about how often police use the weapons to defuse confrontations that might otherwise escalate to use of deadly force. Civil lawyers and department critics have alleged that, rather than deploying Tasers to subdue dangerous criminals, officers have sometimes drawn them on mildly obstinate suspects.
Top-ranking police said they believe officers are using the weapons with restraint, and they gave several explanations as to how skyrocketing Taser use could fail to cut the shooting numbers. Officials initially cited an uptick in attacks on officers, though department statistics indicate that instances of battery of officers actually have dropped.
Department rules grant officers wide latitude in deploying the weapons, authorizing them against both violent assailants and people who run away or make an "evasive movement of the arm." Though Tasers can be valuable tools, experts said, officers generally should not deliver debilitating shocks to people who are fleeing or lightly resisting being handcuffed.
Experts said a police chief should expect an increase in Taser use to cut shootings, if other circumstances remain similar from one year to the next. If shootings are not reduced, a department should question whether something else significant changed or if officers are using force too readily.
"The big investment in Taser is meant to preserve lives," said Roy Bedard, a Florida-based consultant on policing and use of force. "If you're Tasing more people and you're still shooting more people, well, something's wrong."
But Chicago police said conditions on the street never remain stable and cited department statistics indicating that officers are using other kinds of force, including pepper spray and "impact weapons" such as batons, less often. However, the department did not provide detailed data to explain more completely how officers have used other kinds of force since the introduction of the Taser.
Officers need broad discretion to make their own decisions, and they are taught to consider all circumstances before deploying a Taser, said Chicago police Sgt. Michael Partipilo, who is in charge of training police on the devices.
"(Officers) ask me, 'What if this happens?'" he said. "I answer the same, exact way every time: 'I don't know, I can't answer that. You'll have to answer that when you're there.'"
Civil lawyers allege that officers made bad choices in two recent cases, one in which a man claims police shocked him repeatedly and another in which police said an officer jolted a pregnant woman who tore up a parking ticket, threw it at an officer and prepared to drive off.
Officers pulled Josue Tapia from his vehicle after mistaking him for a wanted man in May 2010 and shocked him 11 times, said his lawyer, Blake Horwitz. Tapia was charged with resisting arrest and aggravated battery on a police officer, but he was acquitted in November, according to court records.
"I'm not able to go in public places or even go to work because I feel like something bad is going to happen to me for no good reason," Tapia said.
CPD embraces the Taser
Chicago is a microcosm of Taser International's success at arming police worldwide. The Arizona-based company went from equipping about 500 departments in 2000 to about 16,900 agencies as of this spring, said company spokesman Steve Tuttle.
The weapons, pioneered by a University of Chicago-educated aerospace scientist, fire sharp probes linked to wires that rob their targets of muscular control. Tasers also have a pain compliance mode in which the user gives shocks by pressing the weapon against the target.
Observers disagree on the weapon's safety. Human rights group Amnesty International has counted about 500 deaths following use of an electroshock device in the U.S. since 1990, though many were attributed to other causes.