SAN DIEGO -- A study underway in San Diego is aiming to determine why some people who are shocked with electric stun guns die, while others suffer no ill effects.

The two-year research effort is being challenged because it is being conducted under controlled circumstances and is using healthy trainees at the San Diego Regional Public Safety Training Institute at Miramar College.

Sixty San Diego County sheriff's deputies have volunteered to be monitored by researchers while they train to use the Tasers, which were purchased by the Sheriff's Department in 2006 as a less-lethal alternative to their firearms. The deputies are shot with tasers, which deliver a 50,000-volt electrical shock, during their training.

"In general, more research is good," said Kevin Keenan, executive director of the American Civil Liberties Union office for San Diego and Imperial counties.

But he said his organization is particularly concerned about the effect of stun gun jolts on the heart, especially involving people who are under the influence of alcohol or drugs, the young, the elderly or those with medical conditions.

Research team member Gary Vilke, of the University of California at San Diego, who is a doctor trained in emergency medicine, said the fact that the study does not examine people under the same stress as that endured in a struggle with law enforcement officers is "always the criticism."

"We're trying to see if there are any changes in humans in general," Vilke said. "The first studies were done on pigs."

Deputies are being used because they have already accepted any risks from being stunned as part of their training, said the researcher.

He said the research team, which includes staff from UCSD and San Diego State University, originally wanted to use average people for the study.

However, Vilke said, the investigational review boards at the universities were concerned because stun guns hadn't been tested on humans yet, so they limited test subjects for the research to people who had already accepted the risks as part of their work.

As of March 7, Amnesty International lists 220 people who have died since June of 2001 in the United States after Tasers were used on them, said Mona Cadena, San Francisco deputy director for the western region of that organization.

Rick Poggemeyer, operations administrator at the San Diego County Medical Examiner's office, said there have been at least four deaths involving the use of a Taser during the past six years in this county.

Two involved Tasers used by San Diego police. The other two deaths were in North County.

Nazario J. Solorio, 38, died after Escondido police used a Taser on him in May of 2005. In February Martin Mendoza, 43, died after sheriff's deputies Tasered him in Vista.

Authorities said Solorio had schizophrenia and Mendoza appeared to have some "mental instability" when they struggled with police or deputies, and that both men had histories of drug use.

Custody dea1ths

Vilke, a 40-year-old Scripps Ranch resident, said people who become extremely excited have been dying in law enforcement custody for decades. More than 90 percent of those who die are on drugs and others have psychiatric disorders, he said.

"What we're seeing now is the same population, the same types of people, dying after they've been shot with Tasers," Vilke said. "It's getting more media attention because it's noteworthy, but it's been happening for years."

In recent years, Vilke said, there has been concern about whether the electrical shock would disrupt the person's heart beat, ability to breathe, or acid-based (PH) balances.

"We basically study those three things," Vilke said.

He and three other UCSD staff members who are also doctors trained in emergency medicine, as well as a San Diego State exercise physiologist, started the study in summer of 2005 when there was little research involving the effect of Tasers on humans.

The two-year project is funded by the National Institute of Justice with about $213,000 from the federal U.S. Department of Justice. The institute is the department's research, development and evaluation agency.

During the study's first phase, 30 deputies were monitored before and after a Taser shock to get baseline cardiac data, breathing and metabolic rates, Vilke said.

He said 30 deputies have volunteered for the second part to see how exercise affects a Taser jolt.

Before they're shocked, each deputy will pedal a stationary bicycle to get his or her heart rate up to 80 percent of predicted maximum in an attempt to simulate exertion that might happen in the field.

"It certainly doesn't answer the question, 'Well, they're not on meth either,' and that's always going to be the case," Vilke said.

So far, he said, the researchers haven't seen any physiological effects because of stun guns -- no more acid in the blood, no more electrolytes or other changes.

The only change over time is that enzymes increase from muscle exertion "consistent with light exercise," the researcher said.

"There's nothing that we've found that would cause death with the Taser," Vilke said.

Repeated shocks

Both North County men who died after being shot with a Taser were shocked at least twice while struggling with police or deputies, according to officials.

The medical examiner's office said Solorio died because he couldn't breathe at some point during the struggle and he suffered irreversible brain damage. The autopsy on Mendoza hasn't been completed, pending laboratory results, officials said.

"All the evidence that's out there is very clear that multiple shocks with a Taser would be equivalent to Russian roulette," Cadena said. "The studies that are out there haven't really explored the conditions that could exacerbate the situation."

Those conditions include epilepsy, heart pacemakers, people on medication or who have medical conditions, the mentally ill and substance abusers, she said.

Taser International, the Arizona-based market leader in stun guns, has successfully defended itself against almost 40 wrongful death or injury lawsuits.

Although the company routinely maintains that the Taser is a safer way to control people than using guns, it warned in a 2005 training bulletin that the stun guns should be used with physical restraint techniques.

That should be done in order to minimize the length of any struggle and the use of the Taser, particularly because someone in an "excited delirium" could suffer "significant and potentially fatal health risks" from prolonged exertion as well as impaired breathing, the training bulletin said.

Excited delirium is a disputed condition generally attributed to people who have mental conditions and are frequently under the influence of drugs or extreme stress.

They may appear to be sweaty, their hearts racing, disoriented, unaware of their surroundings.

"The answer is not there as to why they end up in that stage," Vilke said. "We just know it's going on."

He said excited delirium constitutes a medical emergency, but police get involved because the people have been acting irrationally, breaking things and causing other problems.

As far as the medical community is concerned, Vilke said, if someone isn't responding to the shock, that lack of response needs to be viewed as a medical emergency and the person needs to be taken into custody as quickly as possible.

Skeptics remain

John Parker, a former police officer who recently retired as executive director of the county's Citizens Law Enforcement Review Board, is skeptical of using healthy people in a very controlled situation for a Taser study.

"I wouldn't trust the study any further than I could throw it," said Parker. "I would never say you should take the Taser away."

It should be viewed as a less-lethal device with recognition that deaths have happened after Tasers were used, he said.

Parker said since the Sheriff's Department started using Tasers about a year ago the review board has received at least one complaint about use of the stun gun.

"That's a case where a person survived," Parker said. "We've also got the other one (Mendoza)."

Contact staff writer Jo Moreland at (760) 740-3524 or jmoreland@nctimes.com.