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Showing posts with label alex berenson new york times. Show all posts
Showing posts with label alex berenson new york times. Show all posts

Saturday, August 19, 2006

Taser Maker Staunchly Defends Product Even as Bodies Pile Up

August 19, 2006
Mark Silverstein, Rocky Mountain News

The tragic death of 22-year-old Ryan Wilson on Aug. 4th has justifiably refocused public attention on the dangers posed when police officers fire their new high-powered electroshock weapons. Sold by Taser International, Tasers are promoted to the public as devices that can save lives when police would otherwise use firearms. The public is less aware, however, that police departments, with Taser International's blessing, encourage and authorize officers to use Tasers in situations like Ryan's, where no one would claim that firearms are justified.

Nor is the public generally aware of an increasingly common result: more than 200 persons have died shortly after being shocked by law enforcement Tasers. Ryan is the fifth such person to die in Colorado since 2002.

The number of Taser-associated deaths has steadily increased. There were 4 in 2001; 13 in 2002; 20 in 2003; 57 in 2004; 73 in 2005; and an additional 44 so far in 2006.

Most of the deceased posed no serious physical threat to police. Many were extremely agitated or intoxicated. Some had underlying heart problems. Taser International has reported that 80 percent of suspects shocked by Tasers were not brandishing any weapon.

Before the death toll mounts any higher, law enforcement agencies must declare a moratorium. They must immediately stop using Tasers in situations that do not present a substantial threat of death or serious bodily injury.

According to the sparse information released so far, undercover police spotted Ryan near a small patch of marijuana plants. He ran. A Lafayette police officer caught up and discharged an X26 Taser. Ryan immediately began convulsing and died.

With aggressive marketing and a well-oiled PR machine, Taser International has persuaded thousands of law enforcement agencies to buy Tasers. Beginning in 1999, promotional materials hawked the new M26 Advanced Taser as a nonlethal magic bullet that instantly and safely incapacitated suspects without physical struggle. Police departments rely on company-supplied training materials, which continually assure that Tasers are safe, effective and recommended in numerous situations where suspects pose no serious physical threat.

As the bodies began piling up, however, critics began asking whether Taser International had overstated its claims of safety. Company officials scoffed. One spokesperson maintained that Tasers were no more dangerous than Tylenol, while Taser International's president denied the existence of any evidence that Tasers could be dangerous.

Two years ago, Taser International spokespersons claimed that no medical examiner had ever implicated a Taser. As more autopsy reports began listing Tasers as a primary or contributing cause of death, however, ( Amnesty International counted 23 in February ), Taser International argued that coroners were not qualified to assess whether Tasers played a causal role.

Investigative reports by The New York Times and The Arizona Republic have raised serious questions about Taser International's safety claims, its marketing practices, and the reliability of the limited and flawed studies that Taser International cites. After the Securities and Exchange Commission and the Arizona attorney general launched inquires about allegedly deceptive statements, Taser International toned down some rhetoric and recently agreed to pay $20 million to settle a stockholders' lawsuit.

Taser International has always claimed that Tasers cannot produce enough current to cause fatal heart problems. In 2005, however, a U.S. Army memorandum concluded that Tasers could indeed cause ventricular fibrillation. It therefore recommended against shocking soldiers during training exercises.

Earlier this year, a peer-reviewed forensic engineering journal published a study that tested a Taser and concluded that it discharged current far more powerful than Taser International acknowledged - powerful enough to cause fatal heart disrhythmias.

In May, a biomedical engineering professor reported that Tasers caused the hearts of healthy pigs to stop beating, contradicting earlier Taser International-sponsored studies.

Taser International lavishly praises reports that provide qualified support to its safety claims. The company's critics ably dissect those analyses, while Taser International relentlessly grinds out a critique of every study that questions Tasers' safety.

With at least 211 deaths linked to this supposedly nonlethal weapon, however, the Taser proponents must bear the burden of proof in any battle of experts. It is a burden they have not met. There are no reputable independent studies that confirm the manufacturer's assurances of safety, especially in the real-world conditions in which Tasers are actually used and in which suspects actually die.

Law enforcement agencies must stop and question whether they have been sold a bill of goods. Agencies that currently use Tasers must reassess, not only to prevent the deaths of more Ryan Wilsons, but also to spare the public purse from the expensive lawsuits that will surely follow the ever-widening trail of broken bodies and shattered lives.

Thursday, May 25, 2006

The safety of tasers is questioned again

May 25, 2006
By ALEX BERENSON, New York Times

The safety of Tasers, the electric pistols that are widely used by police, is under new scrutiny after a study by a Wisconsin scientist showed that shocks from the guns cause the hearts of healthy pigs to stop beating.

The finding contradicts previous studies that showed that Taser shocks did not cause heart disturbances in pigs, whose hearts are similar to those in humans.

John G. Webster, a professor of biomedical engineering at the University of Wisconsin who conducted the new study, said the earlier studies contained serious errors because they did not account for the fact that pigs have a thick layer of muscle insulating their hearts from their skin. Humans do not.

Dr. Webster removed the muscle from the pigs' chests and placed Taser barbs close to their hearts before shocking the animals. "The previous research made a mistake," Dr. Webster said. "I was a little surprised. But I believe this research more accurately reflects the anatomy of humans."

While most Taser shots land too far from the heart to be lethal, barbs that penetrate the spaces between the ribs that surround the heart may have the potential to cause electrocution, he said.

Steve Tuttle, a spokesman for Taser International, which makes the weapons, said Dr. Webster's research was flawed and did not reflect the way that Tasers were used in humans. The current from a Taser shock is dispersed through the body rather than running directly into the heart, Mr. Tuttle said in an e-mail statement.

The earlier studies on pigs were financed by Taser International. The Justice Department paid for Mr. Webster's study, which is not yet completed. An abstract is posted on Dr. Webster's Web site, http://www.engr.wisc.edu/bme/faculty/webster--john.html

Tasers are pistol-shaped weapons that fire barbs up to 35 feet, delivering a 50,000-volt shock. Because they propel the barbs with compressed nitrogen instead of gunpowder, Tasers are not considered firearms and are not regulated by the Bureau of Alcohol, Tobacco and Firearms or any other federal agency.

Dr. Ted Chan, a professor of clinical medicine at the University of California, San Diego who has studied the effect of Taser shocks on human volunteers, said Mr. Webster's research did not prove that Tasers could cause lethal heart disturbances.

In his research, which is also financed by the Justice Department, Dr. Chan has shocked more than 100 people and not found any changes in heart rhythms. More sophisticated tests conducted on about a dozen people have also failed to find damage, Dr. Chan said.

"Animal studies can point in certain directions, but ultimately you have to look at humans," he said.

Dr. Chan did add that most of the volunteers he tested were not shocked directly over their hearts.

More than 150 people have died after being shocked by Tasers, according to data compiled by Amnesty International, which has called for a moratorium on use of the guns. The weapons are used by almost 10,000 police departments in the United States and internationally, as well as the military. Tasers have been used or tested on volunteers about 200,000 times, Mr. Tuttle said.

Coroners have attributed most of the deaths to causes other than the Taser shock, like cocaine overdoses. But in a handful of cases Tasers have been listed as the primary or contributing cause.

Doctors and scientists have questioned whether Tasers can cause ventricular fibrillation, a lethal heart rhythm disturbance, as well as acidosis, a dangerous change in blood chemistry. Taser International says that many of the deaths have resulted from drug overdoses and that its weapons are safer than most other ways that police officers can use to restrain people.

Since 2002, Tasers have become popular with police departments because they offer officers a way to incapacitate people without having to touch them and because most people do not appear to suffer long-term injury after being shocked. Concerns about safety hurt Taser sales last year, but they have picked up in 2006, with Taser International reporting $14 million in sales in the first quarter.

In October, the Police Executive Research Forum, a nonprofit group that is dedicated to improving police tactics and strategies, recommended that officers be allowed to use the weapons only on suspects who are actively resisting arrest. Some police departments have allowed officers to use Tasers on people who are simply refusing to follow their orders.

The forum's recommendations are not binding. But police departments that do not follow them could face greater legal liability.

Dr. Webster shocked 10 anesthetized pigs with a Taser after removing the skin and muscle over their hearts. On average, the pigs suffered ventricular fibrillation when a Taser barb was placed within 0.7 inch of their heart, according to the abstract of the clinical trial posted on Dr. Webster's Web site. In humans, the heart is situated 0.4 to 2 inches under the skin, Dr. Webster said.

Ventricular fibrillation is an electrical disturbance that causes the heart to beat irregularly and be unable to pump blood. It causes death within minutes unless the heart's normal rhythm is restored.

Wednesday, December 14, 2005

S.E.C. decides not to act against taser on safety statements

December 14, 2005
By ALEX BERENSON, New York Times

The Securities and Exchange Commission has decided not to take action against Taser International in connection with statements about the safety of its electric stun pistols, the company said yesterday.

Taser's shares jumped 15 percent on the news, though they remain far below the highs they set a year ago. They closed at $7.04, up 92 cents. They closed at $32.59 on Dec. 30 last year.

The company's pistols, called Tasers, which are widely used by police to subdue suspects, have been associated with more than 140 deaths. The weapons fire electrified barbs up to 25 feet, delivering a painful 50,000-volt shock.

Taser's sales and profits soared in 2004, but the company's profits have plunged this year as controversy over the safety of its weapons has grown. In November, an influential police research group recommended new restrictions on the use of the weapons, suggesting that officers be allowed to use them only on people who are actively resisting arrest.

Last month, Taser said it would have to restate its profits for the first half of 2005 because it had failed to properly record its legal and professional expenses during that period. The company also failed to file its third-quarter financial statements within the Nasdaq's deadline for filing, leading the Nasdaq to warn that Taser stock would be delisted. Taser has appealed the delisting requirement.

In January, Taser announced that the S.E.C. had begun an investigation into the company's statements about the safety of its stun guns and a sales order that it announced in late December 2004. Taser said in a statement yesterday that S.E.C. enforcement officials had told the company that they had completed the investigation and had decided against taking action against the company.

Taser also said that the S.E.C. was ''continuing to investigate issues relating to trading in the company's stock.''

As a matter of policy, the S.E.C. does not comment on its investigations.

Friday, September 02, 2005

Doctors blame taser stun gun for fibrillation

September 2, 2005
ALEX BERENSON, New York Times

A shock from a Taser stun gun caused a teenager in Chicago to go into ventricular fibrillation, a usually fatal heart disturbance, according to a letter published yesterday in The New England Journal of Medicine.

The letter, written by two doctors at Children's Memorial Hospital in Chicago, appears to be the first medically documented case of ventricular fibrillation caused by a Taser gun. Tasers are pistol-like weapons that fire electrified barbs up to 25 feet, immobilizing people with painful shocks.

Taser International, which makes the guns, has said that Tasers cannot cause fibrillation, a condition in which the heart loses the ability to pump blood. If not immediately reversed, fibrillation causes death within minutes. In the Chicago case, which occurred last February, the teenage crime suspect received immediate medical attention and survived after the police shot him with the Taser.

Dr. Wayne H. Franklin, a pediatric electrophysiologist at Children's Memorial and one of the letter's authors, said the teenager would have died if he had not been received immediate care. An electrocardiogram or heart rhythm test, administered to the teenager, proved that he suffered fibrillation, Dr. Franklin said.

The case illustrates the risks of Tasers as well as the need for police officers to carry automated defibrillators, which put out a large electric shock that restores the heart's rhythm, Dr. Franklin said. Police officers should be aware that Tasers can cause fibrillation, even though the risks may be small, he said.

"I don't know why it happens to one person and why it doesn't happen to another," he said. "Not everyone who gets hit by lightning dies, either."

In response to the letter, Taser forwarded an e-mail message from Dr. Richard M. Luceri, director of the Arrhythmia Center at Holy Cross Hospital in Fort Lauderdale, Fla., in which he said: "The conclusion implied by the authors is purely speculative and not backed by scientific evidence."

About 130 people have died after being shocked by a Taser, including nearly 70 in the last 12 months, according to Amnesty International, which has called for a moratorium on the use of the guns. In most cases, autopsy reports have not found the Taser to be the cause of death.

In 2003 and 2004, use of Tasers spread rapidly among American police departments as officers sought ways to control suspects without fighting with them or using firearms.

But sales of the guns have plunged this year amid safety questions. Tasers cause the muscles to contract uncontrollably. Repeated Taser shocks may cause the blood to become highly acidic and the body to overheat, both potentially fatal conditions, scientists say.

Friday, November 26, 2004

Claims Over Tasers' Safety Are Challenged

November 26, 2004
Alex Berenson, The New York Times

Taser International, whose electrical guns are used by thousands of police departments nationwide, says that a federal study endorses the safety of its guns, but the laboratory that conducted the research disagrees.

Taser said last month that the government study, whose full results have not yet been released, found that its guns were safe. Since that statement, the company's stock has soared and its executives and directors have sold $68 million in shares, about 5 percent of Taser's stock and nearly half their holdings.

But the Air Force laboratory that conducted the study now says that it actually found that the guns could be dangerous and that more data was needed to evaluate their risks. The guns "may cause several unintended effects, albeit with low probabilities of occurrence," the laboratory said last week in a statement released after a symposium on Tasers, as the company's guns are known, and other weapons intended to incapacitate people without killing them.

Taser said Wednesday that it stood behind its October statement.

Other data presented at the symposium raised questions about one of Taser's key claims about the effectiveness of its newest and most expensive weapon.

Tasers are pistol-shaped weapons that fire electrified darts up to 21 feet, shocking suspects with a painful charge. More than 5,500 police departments and prisons now use Tasers, compared with only a handful five years ago.

Many police officers say that Tasers give them a way to restrain dangerous suspects without using firearms or fighting with them. But civil liberties groups say police often use Tasers on people who are merely unruly or disobedient, not dangerous. Recently, police officers in Miami shocked a 6-year-old boy and a 12-year-old girl in separate incidents, prompting widespread criticism.

"The evidence suggests that far from being used to avoid lethal force, many police forces are using Tasers as a routine force option," said Curt Goering, senior deputy executive director of Amnesty International. "The way these weapons are being used in some circumstances could constitute torture or ill treatment."

Amnesty has called for police departments to stop using the guns pending an independent inquiry into their safety. The group will release a report next week documenting police abuse of Tasers, Mr. Goering said.

The growing use of Tasers is disconcerting because their risks have not been properly studied, biomedical engineers say. More than 70 people have died since 2001 after being shocked with Tasers, mainly from heart or respiratory failure.

Taser International says the deaths resulted from drug overdoses or other factors and would have occurred anyway. But coroners have linked several deaths to the weapons, and independent scientists who are authorities on electricity and the heart say that the company may be significantly underestimating the weapon's risks, especially in people who have used drugs or have heart disease.

Taser has performed only minimal research on the health effects of its weapons. Its primary safety studies on the M26, its most powerful gun, consist of tests on a single pig in 1996 and on five dogs in 1999. The company has resisted calls for more tests, saying that it is comfortable with the research it has conducted.

Tasers are largely unregulated and have never been studied for their safety or effectiveness by the Consumer Product Safety Commission or the Bureau of Alcohol, Tobacco, Firearms and Explosives. But for two years the Defense Department has studied Tasers as part of military research into weapons designed to be effective without being deadly.

In a press release on Oct. 18, Taser said that the military study had found its guns "generally effective without significant risk of unintended consequences."

Rick Smith, the chief executive of Taser, called the study "the latest chapter in a series of comprehensive medical and scientific studies which conclude that Taser technology is safe and effective."

Taser's stock, which closed at $37.47 on Oct. 15, the last trading day before the study was released, rose 60 percent over the next month and peaked at $60.85 on Nov. 15. During the week ended Nov. 12, Taser executives and directors sold 1.28 million shares for $68 million. The company's stock closed Wednesday at $50.51, down 89 cents.

But neither Taser nor the military released the full study, only an excerpt. The full study remains confidential, military officials say. But last week, after the symposium on less-deadly weapons in Winston-Salem, N.C., the Air Force laboratory that conducted the study said that it had not found Tasers were safe.

The guns "may cause several unintended effects, albeit with estimated low probabilities of occurrence," the laboratory said. "Available laboratory data are too limited to adequately quantify possible risks of ventricular fibrillation or seizures, particularly in susceptible populations."

Ventricular fibrillation is a disturbance of the electrical circuitry of the heart that causes cardiac arrest in seconds and death in minutes. Taser says that its weapons do not produce enough current to cause ventricular fibrillation, but scientists who are authoritative on fibrillation say that the company has not done enough research to know whether that contention is accurate.

Taser said Wednesday that the military had reviewed and approved its October statement before the company released it.

An Air Force scientist presented data at the symposium last week showing that repeated Taser shocks caused pigs to become acidotic - a dangerous condition in which the pH of the blood drops. A 1999 study by the Justice Department suggested that "deaths following Tasers' use may be due to acidosis."

People who have been hit repeatedly by Tasers should receive medical monitoring, said Dr. James Jauchem, the Air Force scientist. A spokeswoman for the Air Force said Wednesday that Dr. Jauchem was on vacation for Thanksgiving and not available for additional comments.

Dr. Jauchem also presented data calling into question the company's assertion that the Taser X26, its newest gun, is especially effective even though it fires a smaller charge than the company's older weapon, the M26. Taser has said that the X26 fires a special kind of electric pulse that works better than traditional stun guns.

But Dr. Jauchem said the shape of the X26's electric pulse had only a minor effect on the amount of muscle contraction it produced.

Taser falls on New York Times report

November 26, 2004
By Jim Jelter, CBS MarketWatch.com

SAN FRANCISCO (CBS.MW) -- Shares of stun-gun maker Taser International tumbled Friday, hit by a New York Times report that raised new safety concerns about the company's main product line. The article in the New York Times, citing unpublished results of Air Force Research Laboratory tests, adds to a growing body of complaints over the use and safety of Taser's stun guns. According to the paper, the Air Force said at a symposium last week that Taser stun guns may be dangerous and require further testing. The Air Force's comments fly in the face of a recent federal study that called Taser's products "generally safe and effective." Company executives could not be reached for comment. Scottsdale, Ariz.-based Taser markets its guns as nonlethal self-protection devices, with law enforcement agencies and security companies making up its biggest customer base. According to the company, its products send a nonlethal jolt of electricity to subdue the target body. But there has been a rash of complaints in recent months blaming Taser stun guns for accidental injuries, raising the specter of debilitating lawsuits. Taser shares have shed about 13 percent of their value in just the past two weeks.

Sunday, July 18, 2004

Claims for Taser safety based on pig, dog tests

July 18, 2004
Alex Berenson, New York Times

As police use of tasers rises, questions over safety increase

July 18, 2004
Alex Berenson, The New York Times

AZARETH, Pa. — As the sun set on June 24, something snapped in Kris J. Lieberman, an unemployed landscaper who lived a few miles from this quiet town. For 45 minutes, he crawled deliriously around a pasture here, moaning and pounding his head against the weedy ground.

Eventually the police arrived, carrying a Taser M26, an electric gun increasingly popular with law enforcement officers nationwide. The gun fires electrified barbs up to 21 feet, hitting suspects with a disabling charge.

The officers told Mr. Lieberman, 32, to calm down. He lunged at them instead. They fired their Taser twice. He fought briefly, collapsed and died.

Mr. Lieberman joined a growing number of people, now at least 50, including 6 in June alone, who have died since 2001 after being shocked. Taser International, which makes several versions of the guns, says its weapons are not lethal, even for people with heart conditions or pacemakers. The deaths resulted from drug overdoses or other factors and would have occurred anyway, the company says.

But Taser has scant evidence for that claim. The company's primary safety studies on the M26, which is far more powerful than other stun guns, consist of tests on a single pig in 1996 and on five dogs in 1999. Company-paid researchers, not independent scientists, conducted the studies, which were never published in a peer-reviewed journal. Taser has no full-time medical director and has never created computer models to simulate the effect of its shocks, which are difficult to test in human clinical trials for ethical reasons.

What is more, aside from a continuing Defense Department study, the results of which have not been released, no federal or state agencies have studied the safety, or effectiveness, of Tasers, which fall between two federal agencies and are essentially unregulated. Nor has any federal agency studied the deaths to determine what caused them. In at least two cases, local medical examiners have said Tasers were partly responsible. In many cases, autopsies are continuing or reports are unavailable.

The few independent studies that have examined the Taser have found that the weapon's safety is unproven at best. The most comprehensive report, by the British government in 2002, concluded "the high-power Tasers cannot be classed, in the vernacular, as `safe.' " Britain has not approved Tasers for general police use.

A 1989 Canadian study found that stun guns induced heart attacks in pigs with pacemakers. A 1999 study by the Department of Justice on an electrical weapon much weaker than the Taser found that it might cause cardiac arrest in people with heart conditions. In reviewing other electrical devices, the Food and Drug Administration has found that a charge half as large as that of the M26 can be dangerous to the heart.

While Taser says that the M26 is not dangerous, it now devotes most of its marketing efforts to the X26, a less powerful weapon it introduced last year. Both weapons are selling briskly. About 100,000 officers nationally now have Tasers, 20 times the number in 2000, and most carry the M26. Taser, whose guns are legal for civilian use in most states, hopes to expand its potential market with a new consumer version of the X26 later this summer.

For Taser, which owns the weapon's trademark and is the only company now making the guns, the growth has been a bonanza. Its stock has soared. Its executives and directors, including a former New York police commissioner, Bernard B. Kerik, have taken advantage, selling $60 million in shares since November.

Patrick Smith, Taser's chief executive, said the guns are safe. "We tell people that this has never caused a death, and in my heart and soul I believe that's true," Mr. Smith said.

Taser did not need to disclose the British results to American police departments, he said. "The Brits are extremely conservative," he said. "To me, this is sort of boilerplate, the fine print." In addition to Taser's animal trials, thousands of police volunteers have received shocks without harm, Mr. Smith said.

But the hits that police officers receive from the M26 in their Taser training have little in common with the shocks given to suspects. In training, volunteers usually receive a single shock of a half-second or less. In the field, Tasers automatically fire for five seconds. If an officer holds down the trigger, a Taser will discharge longer. And suspects are often hit repeatedly.

Over all, Taser has significantly overstated the weapon's safety, say biomedical engineers who separately examined the company's research at the request of The New York Times. None of the engineers have any financial stake in the company or any connection with Taser; The Times did not pay them.

Relatively small electric shocks can kill people whose hearts are weakened by disease or cocaine use, said John Wikswo, a Vanderbilt University biomedical engineer. But no one knows whether the Taser's current crosses the threshold for those people, Dr. Wikswo said.

"Their testing scheme has not included the possibility that there is a subset of the population that is exquisitely sensitive," Dr. Wikswo said. "That alone means they have not done adequate testing."

Mr. Smith said Taser would eventually run more tests. "In a perfect world, I'd love to have studies on all this stuff, but animal studies are controversial, expensive," he said. "You've got to do the reasonable amount of testing." Comparing Taser's tests with the studies conducted by makers of medical devices like pacemakers is unfair, he said.

Dr. Andrew Podgorski, a Canadian electrical engineer who conducted the 1989 study, said he was certain that Tasers were dangerous for people with pacemakers. More research is needed to determine if other people are vulnerable, he said.

"I would urge the U.S. government to conduct those studies," Dr. Podgorski said. "Shocking a couple of pigs and dogs doesn't prove anything."

In More Officers' Hands

Many police officers defend the Taser, saying the weapon helps them avoid using deadly force and lowers the risk of injury to officers. Tasers let police officers subdue suspects without wrestling with or hitting them, said David Klinger, a former police officer and a criminology professor at the University of Missouri at St. Louis. And Tasers are surely safer than firearms.

"I think it is appropriate for deployment in the field," Mr. Klinger said. "You trust this guy or gal with a gun, you should be able to trust them with a less lethal device."

But human rights groups say the police may be overusing the Taser. Because the gun leaves only light marks, and because Taser markets it as nonlethal, officers often use it on unruly suspects, not just as an alternative to deadly force, said Dr. William F. Schulz, the executive director of Amnesty International USA. In recent incidents, officers have shocked a 9-year-old girl in Arizona and a 66-year-old woman in Kansas City.

"We think there should be controlled, systematic independent medical studies," Dr. Schulz said. "We would like to see these weapons suspended until these questions are answered."

A study by the Orange County, Fla., sheriff's office showed that officers used pepper spray and batons much less after getting the guns. But the use of Tasers more than made up for that drop, and the department's overall use of force increased 58 percent from 2000 to 2003. Last week, several police departments in Orange County agreed to restrict the use of Tasers to situations where suspects are actively resisting officers. The sheriff's office is not part of the agreement and says it is still studying the matter.

State and federal agencies do not keep tabs on Taser use, so no one knows how many times officers have fired the weapon. Officers have reported close to 5,000 uses of the M26 to Taser, but the company says the actual number is much higher.

Little evidence supports the theory that Tasers reduce police shootings or work better than other alternatives to guns, like pepper spray. Because of their limited range, Tasers are best in situations where an officer using a Taser is covered by another with a firearm, officers say.

A 2002 company study found that nearly 85 percent of people shocked with Tasers were unarmed. Fewer than 5 percent were carrying guns.

In Phoenix, which has equipped all its officers with Tasers, police shootings fell by half last year. Taser trumpets that statistic on its Web site. But last year's drop appears to be an anomaly. This year, shootings are running at a record pace, according to the Phoenix police department.

A 2002 study in Greene County, Mo., found that Tasers were only marginally more effective than pepper spray at restraining suspects. Pepper spray worked in 91 percent of cases, while the Taser had a 94 percent success rate.

The largest police departments have been slow to embrace the Taser. The New York Police Department owns only a handful of Tasers, which are used by specialized units and supervisors, a spokesman said.

'Gold in Those Hills'

The M26 was introduced only five years ago, but the technology is much older. John Cover, an Arizona inventor, created the Taser in 1969. Its name stands for "Thomas A. Swift Electric Rifle," an allusion to the Tom Swift series of science fiction novels.

Engineers have known for generations that relatively small electric currents cause painful and uncontrollable muscle contractions. Tasers operate on that principle, firing barbs that are connected by wire to the gun and flood the body with current. The gun can deliver its shock even if the barbs do not break the skin because its current can jump through two inches of clothing.

Weak currents are not inherently dangerous if they stop in a few minutes. But stronger shocks can disrupt the electrical circuitry of the heart. That condition, ventricular fibrillation, causes cardiac arrest in seconds and death in minutes, unless the heart is defibrillated with an even larger shock.

The exact current needed to cause fibrillation depends on technical factors like the current's shape and frequency, as well as the heart's condition, said James Eason, a biomedical engineering professor at Washington and Lee University. But because fibrillation is so dangerous, scientists can conduct only limited human trials. They must estimate the threshold of fibrillation from animal trials and computer models.

Still, the broad parameters for fibrillation are known, and the first Taser from Mr. Cover had a large safety margin. In 1975 the Consumer Product Safety Commission concluded that weapon, which was 11 percent as powerful as the M26, probably would not harm healthy humans.

Then, in March 1976, the Bureau of Alcohol, Tobacco and Firearms claimed it had jurisdiction over the weapons because gunpowder propelled their barbs. The firearms bureau essentially outlawed them for civilian use; no federal safety standard was ever created.

But the original Tasers were bulky and often ineffective. For almost two decades, they remained a niche product used by a few police departments.

That began to change after 1993, when Mr. Smith and his brother Thomas created a company to market electric weapons to civilians. Patrick Smith, who had just graduated from the University of Chicago business school, saw enormous potential for an alternative to firearms.

"I just figured I'm going to go to out to Arizona, and I'm going to scratch and sniff and dig, and figure there's going to be gold in those hills," Mr. Smith said in an interview.

In January 1995, the Smiths introduced their first electric gun, which was powered by compressed nitrogen. As a result, the weapon was not regulated by the firearms bureau and could be sold to civilians.

For the next several years, the company struggled, as concerns over the gun's power kept sales slow. By 1999, the company, now known as Taser International, was near bankruptcy, with only $50,000 in the bank and $2.7 million in debt.

"It was pretty humiliating," he said. "We had completely wiped out my parents financially."

Testing

Hoping to stay afloat, the company introduced the Advanced Taser M26 in December 1999. The weapon closely resembled a handgun, a feature many police officers liked, and was very powerful.

According to Taser, the gun produced 26 watts of power, four times the power of the earlier model. A field test in 2001 by the Canadian police showed that the M26 was even stronger, with an output of 39 watts.

(Stun gun power is usually gauged in watts, a measure of electrical energy, even though the biological effects of electricity are more closely related to current strength, measured in amperes. Electrical engineers often compare the flow of electricity to a river: amperes are like the river's speed, while watts are the amount of water flowing by each second. As watts increase, amperes rise, but more slowly.)

Taser's sales rose as officers learned about the new gun. At meetings with police officers, company representatives encouraged them to receive a half-second shock to feel the weapon's power for themselves. "These guys would leave just absolutely evangelical about the product because we would just drop them all," Mr. Smith said.

In its marketing, the company touted the safety of the M26, saying it had been extensively tested.

But Taser had performed only two animal studies before introducing the M26.

In 1996, Taser hired Robert Stratbucker, a Nebraska doctor and farmer, to test the weapon. Dr. Stratbucker, who is now Taser's part-time medical director, shocked a pig 48 times with shocks as large as those from the M26. The pig suffered no heart damage.

Three years later, the company hired Dr. Stratbucker and Dr. Wayne McDaniel, an electrical engineer, for an animal test at the University of Missouri. The scientists shocked five anesthetized dogs about 200 times with the M26. The dogs did not suffer cardiac arrest, although one animal had changes in its heartbeat, according to a report.

Taser has repeatedly said the studies proved that the M26 was safe. But the biomedical engineers who reviewed the gun's safety for The Times said Taser should have conducted far more research.

"I don't think there has been a definitive study saying that yes it can contribute to death or no it cannot," said Dr. Raymond Ideker, an electrophysiologist and a professor in the cardiology division at the University of Alabama at Birmingham. Taser must test more animals and vary the shocks they receive to find the gun's safety margin, Dr. Ideker said.

In addition, while Taser claims that its Missouri study proves that the gun is safe for people who have used cocaine, it never tested animals dosed with cocaine. Because cocaine substantially increases heart attack risk, and Tasers are used on people who have taken cocaine, that omission is a serious flaw, said Dr. Wikswo of Vanderbilt.

The company should also examine risks other than fibrillation, some scientists say.

Dr. Terrence Allen, a former medical examiner in Los Angeles who examined cases in the late 1980's when people died after being shocked with earlier-model Tasers, said he was sure the weapons could be lethal. Taser is misrepresenting the medical evidence, said Dr. Allen, who has consulted for people who have sued the company.

Dr. Mark W. Kroll, a Taser director and the chief technology officer of St. Jude Medical, one of the largest pacemaker manufacturers, said Taser had adequately tested its weapons and they were safe. External pacemakers deliver much larger charges and do not cause fibrillation, he said.

Dr. Ideker countered that pacemakers and Tasers could not be easily compared, because the Taser's shock is very short and powerful, while a pacemaker delivers its charge over a much longer period.

Although Taser has performed only rudimentary studies of the M26, it has more closely studied the X26, the gun it introduced last year. In a 2003 study at the University of Missouri, Taser found that a shock roughly 20 times that of the X26 caused a healthy, anesthetized 85-pound pig to fibrillate.

Mr. Smith cites the 2003 Missouri study as proof that all Tasers have a safety margin of 20-to-1 or more. But the new gun puts out a charge only one-fourth as large as the older model, a fact Taser does not generally advertise.

The study said nothing about the M26, or about hearts stressed by disease, drugs or physical activity. "I think another test is warranted," Dr. Ideker said.

Taser did not test the older gun, which is associated with nearly all the deaths, because "we believed that the M26's safety record and prior testing speaks for itself," Mr. Smith said. "Could it be done? Absolutely. There's time and expense involved."

The X26 has become Taser's biggest seller, based mainly on the company's claims that it is even stronger than the M26 despite its small size and lower power. The company says the new gun enables electrical current to enter the body more efficiently.

No independent agency has tested the guns side by side, and in Taser's patent on the M26, Mr. Smith himself argued that weaker guns were often ineffective because they do not deliver enough current to incapacitate suspects. But neither deaths nor concerns about effectiveness have dampened police support and investor enthusiasm for Taser International. Stock analysts predict Taser will have $15 million in profits on sales of $60 million in 2004. Investors have bid up the company's shares 60-fold since last February, giving Taser a value of $1.2 billion.

The Smith brothers and their father, Phillips, have sold $46 million in Taser shares since November, according to federal filings. They still own $130 million worth of shares. Other Taser executives and directors have sold $14 million in stock. Mr. Kerik, the former New York police commissioner and a director, has sold $900,000 in stock. Mr. Kroll of St. Jude Medical has sold $1.7 million.

"It's been great," Patrick Smith said of the company's recent success. But making money is not his main goal, he said. "If we could get a Taser on every officer's belt,'' he said, " it would save hundreds of lives or thousands of lives a year."

Deaths and Questions

Meanwhile, the number of Taser-associated deaths is rising. In June alone, at least six people died, the most ever in one month: Eric B. Christmas, James A. Cobb, Jacob J. Lair, Anthony C. Oliver, Jerry W. Pickens and Mr. Lieberman.

The circumstances of the deaths vary widely. Among the six, Mr. Pickens was the only one hit with the X26.

Mr. Cobb fought for several minutes after being shocked, which suggests that fibrillation could not have caused his death. Some of the other men collapsed immediately, according to news reports and witnesses. Some of the men were fighting with the police when officers shot them. Others simply refused to obey orders.

Mr. Pickens was one. On June 4, in Bridge City, La., the police were summoned to help calm him after an argument with his 18-year-old son, Taylor Pickens. Jerry Pickens confronted the police in the family's front yard.

"My dad, he had been drinking, and he was kind of hostile toward the police,'' Taylor said. "He kept trying to go back inside the house, and they said, 'If you're going to go back into the house we're going to Taser you.' " Mr. Pickens who was unarmed, began to walk inside, Taylor said.

"They counted down three, and then they shot him in the back," Taylor said. "My dad stiffened up, and fell back." Mr. Pickens hit his head on a cement walkway and began foaming at the mouth, Taylor said.

Sharon Landis, Taylor's mother and Mr. Pickens's wife, said officers did not need to shock her husband. "They could have pepper-sprayed him, they could have grabbed him," she said. "He's 55 years old, and these are big burly cops."

Mr. Pickens was pronounced brain-dead that day and removed from life support three days later, Ms. Landis said.

Toxicologic tests on Mr. Pickens are being conducted, said Gayle Day of the Jefferson Parish coroner's office. A spokesman for the sheriff's office said he could not comment on a continuing investigation. Mr. Smith said he could not comment on Mr. Pickens's death.

Three weeks later, Kris Lieberman died in Pennsylvania. The officers who shocked him were the only witnesses to his death, which the Pennsylvania State Police are investigating. But Mr. Lieberman's parents said the state police told them that their son was shocked twice and collapsed afterward. [Stan Coopersmith, chief of the Bushkill Township Police, whose officers responded to the call, said he could not comment on the incident until the state police finish their investigation.] But Taser said that the police chief had told the company that Mr. Lieberman fought briefly after the shocks and that an automatic defibrillator used by the officers indicated Mr. Lieberman was not fibrillating when he collapsed.

"I would suspect the autopsy will find a cause of death that does not include the Taser," Mr. Smith said.

Mr. Lieberman's parents say that he was troubled but that he did not use drugs. Police officers searched Mr. Lieberman's home after the shooting and did not find drugs, his parents say. Toxicologic tests are pending, the Northampton County Coroner said.

Mr. Lieberman's father, Richard, a plain-spoken farmer, said he had not decided whether to hire a lawyer. He simply wants to know if the gun caused his son's death. "If he was the problem, we have to accept it," Mr. Lieberman said. "If they were the problem, they have to accept it."

Eric Dash contributed reporting from New York for this article.