The ideal nonlethal weapon has been around for decades.
Invented in 1966, it can instantly stun a person into unconsciousness with no ill effects. And with the flip of a switch, the same weapon can vaporize a threat into oblivion.
But the "Star Trek" phaser is just a Hollywood prop. Otherwise, every cop in America would carry one.
Instead, modern police rely on a variety of nonlethal weapons with an array of technologies in their quest to keep the peace without resorting to deadly force.
"We need the ability to enforce the law without killing the suspect no matter how evil they might be," said Charles "Sid" Heal, a nonlethal weapons expert and a retired Los Angeles County sheriff's deputy.
Nonlethal weapons help officers carry out their most basic duty of taking suspected lawbreakers into custody with minimal harm so they can go before a judge, said Steve Ijames, retired deputy police chief in Springfield, Mo., and a nonlethal weapons expert.
"Officers are not justice on the street," Ijames said. "We don't hand out justice. Justice is handed out by a judge and a jury."
DEADLY FORCE ALTERNATIVES SOUGHT
The idea of modern alternatives to deadly force emerged in the mid-1960s when President Lyndon B. Johnson created a crime commission in the wake of widespread civil unrest. The commission studied the underlying causes of crime, but it also touched on the need to develop new weapons to safely deal with riots. At the time, police had guns, clubs and tear gas.
Inspired by the commission's message, physicist Jack Cover soon developed the first Taser. About the same time, a hand-held Mace canister of chemical spray and beanbag rounds for shotguns were invented, both precursors to the nonlethal weapons police use today.
Retired Los Angeles Police Department Capt. Greg Meyer recalled his own assignment to find nonlethal alternatives for his agency after an egregious shooting in 1979. His agency's early adoption of the Taser led to a dramatic reduction in injuries compared to the baton, he said.
However, it would take two decades and more development before the Taser gained widespread use.
Developed in the late 1980s, pepper spray was widely adopted in the 1990s. And like the Taser, it was the subject of controversy when it emerged.
The American Civil Liberties Union linked the spray, which irritates the mucus membranes of the eyes, nose and throat, to deaths after encounters with police.
"The ACLU was as against pepper spray then as they are against Taser now," Ijames said.
Further scientific studies disproved those links, and today pepper spray is widely used.
TASER IS 'BEST THING WE HAVE'
Most nonlethal weapons used by police through the years rely on pain compliance to bring a suspect into custody.
"Pain compliance works. We know it works. It's been around for thousands of years," Heal said.
However, some people, especially the mentally ill and those high on drugs, can be immune to pain compliance, making weapons such as the baton and pepper spray virtually useless.
Batons and beanbag rounds are effective about 70 percent of the time, while pepper spray is effective in about 85 percent of uses.
The Taser doesn't rely on pain compliance to stop a suspect. It uses electricity to involuntarily lock up a suspect's muscles, allowing officers to take the person into custody.
The shock is delivered through two wires that connect to the target's body with barbed ends and is effective about 94 percent of the time.
"We'll be the first ones to admit it's not everything we want, but it's the best thing we have," Heal said.
Like pepper spray before it, the Taser became a target for critics such as Amnesty International, which has linked the Taser to more than 460 deaths nationwide since 2001. A study by the group linked Las Vegas police to six Taser-related deaths between 2001 and 2008, the most in the country.
Heal called studies linking Tasers to hundreds of deaths "voodoo science."
"They have fueled the fear without the science," Heal said.
Only a few medical examiners have said the Taser contributed to a death, and more than 2 million people, including officers, have been shot with the weapon without dying, he said.
"The alternative if we don't use these things on the person with a knife, we'll just shoot him," Heal said.
Other studies, including recent research by the National Institute of Justice, concluded that Tasers are highly effective in reducing injuries to both officers and suspects and have a low chance of causing death.
Las Vegas police use their Tasers and other nonlethal weapons depending on the situation and the suspect's actions. For example, officers might use a beanbag shotgun or Taser against someone holding a knife but not threatening anyone. But if that person rushes the officers, they would likely use their guns because of the immediate threat to themselves or others.
OVERCOMING OVERUSE OF TASERS
Ijames predicted people in 50 years will call the Taser the single-greatest invention in law enforcement. That doesn't mean it's without problems.
He said overuse of Tasers early on "did more to damage our credibility with the public than at any other time in our history."
Early research showed officers were far less likely to be injured if they used the Taser at the start of a confrontation, which prompted officers to use them early and often instead of relying on their verbal skills and hands-on tactics to de-escalate situations, he said.
That led to incidents such as drivers being shot with a Taser for refusing to show a license, Ijames said.
But in recent years, police have adapted Taser policies to limit their use. For example, Taser shocks for passive resistance have been barred, as well as use on children and older people.
There have also been limits on how often a person can be shocked and situational limits, such as not shooting someone who could be injured in a fall.
At the Metropolitan Police Department, officers used a Taser, pepper spray or other nonlethal weapon in 11 percent of incidents where they also used firearms, and initially fought hand to hand in 8 percent of incidents, since 1990 .
The department, which has a national model Taser policy, has seen use of the stun guns fall from about 24 percent of all use of force incidents in 2004 to 16 percent last year. Officer Marcus Martin attributed the drop to training that reinforces using other skills before resorting to the Taser .
However, the American Civil Liberties Union still believes the weapon is used too much by Las Vegas police.
"Tasers are a useful tool, just like handguns are a useful tool, and need to be used only sparingly," said Allen Lichtenstein of the ACLU of Nevada.
Since it can be deadly, the Taser should be used only as an alternative to deadly force, he said.
Whether the Taser reduces police shootings remains unclear.
Some research indicates it does, but mostly there's only anecdotal evidence.
University of South Florida criminology professor Lori Fridell and other researchers tried to answer that question in a recent National Institute of Justice study, but they determined there isn't enough data yet for a statistically relevant conclusion.
"It is one more weapon in the (officer's) arsenal that fills the gap between hands and feet and their weapon," Fridell said.