A lawsuit in Arizona, the first to go to trial, alleges the manufacturer didn't sufficiently test the gun for potential risks.
What was hailed as the best new tool on a police officer's belt has wound up in court after a number of complaints over its safety.
Makers of the Taser stun gun are having to defend the device - and the claims they made about its health risks - in the first such case to make it to trial. The lawsuit contends that a shock by the stun gun in 2002 ended the career of a sheriff's deputy in Maricopa County, Ariz.
It is the first of some 35 personal-injury, wrongful-death, or excessive-use-of-force lawsuits that have been filed against Taser International. Executives at the company in Scottsdale, Ariz., have vowed to fight them all in court, saying studies show their product is safe and does not cause serious injury or death.
In fact, earlier this month, Taser announced that use of its stun gun had saved an estimated 9,000 lives because police did not have to reach for a gun.
But a growing number of coroners across the country have cited Tasers as a contributing factor in accidental deaths. These and other questions about their safety have led some police departments to ban their use. They've also prompted an inquiry by the US Securities and Exchange Commission into claims the company has made about safety studies. In addition, the company's stock - formerly one of the market's best performers - has plunged.
Resembling a small pistol, the stun guns use nitrogen cartridges to propel darts into the body, delivering a 50,000-volt shock. Lasting several seconds, the shock immobilizes a person, thereby allowing officers to take control of the situation.
Police agencies began buying the stun guns in large quantities in 1999 and again in 2003 when the company reduced the product's size and weight. They are now used in more than 8,000 law-enforcement agencies across the country and are spreading into the US military.
They were initially well received by police departments that were looking for ways to reduce the number of fatal shootings by officers. Some indeed began to see dramatic declines after introducing the stun guns.