UN Says Tasers Are a Form of Torture
The use of Tasers "causes acute pain, constituting a form of torture," the UN's Committee Against Torture said. "In certain cases, they can even cause death, as has been shown by reliable studies and recent real-life events." Three men — all in their early 20s — died from after tasering in the United States this week, days after a Polish man died at Vancouver airport after being tasered by Canadian police. There have been 17 deaths in Canada following the use of Tasers since they were approved for use, and 275 deaths in the US. "According to Amnesty International, coroners have listed the Taser jolt as a contributing factor in more than 30 of those deaths."
Weapon involved? Tasers are good in this case. Unfortunately, tasers are not used in that manner exclusively. They are also used to "calm people down", saving the cop from having to communicate with the individual. This is unacceptable. Pulling your arm away from a cop who is trying to grab you is not immediate justification to tase (see "don't tase me, bro!") since it might very well be considered a natural reaction. And "don't let a few bad apples spoil the whole bunch" has been considered. When 80 year old, wheelchair-bound schizophrenic women are being tased (and subsequently, end up dead) because the cops are too scared to handle the situation as they were trained, then tasers are obviously too much responsibility for them to handle.
What usually happens is that these people are in such an agitated state that when approached by law enforcement (or a security guard, or some shopkeeper who is trying to get them out of the store, or some passerby trying to get them out of running down the middle of the road in heavy traffic) tend to get even more aggressive and attack, and don't respond to the usual methods of being subdued like pepper spray or threat of arrest or being shot or anything. It can and and often does take 4 or 5 heavily trained policemen to get these guys out of danger. What has happened in the past is that these people continue to fight even when restrained in handcuffs, and then die of a sudden cardiac event most likely due to all the excitement and inability to calm down due to whatever drugs they are on. Over the years this has been well recognized and most sensible jurisdictions have rules such as "once handcuffed do not place in prone position" due to higher chances of these people dying from positional asphyxia.
Anyways, back to the Taser thing. Taser for years and years have been saying that since these deaths can happen WITHOUT the use of a Taser, then it's reasonable to assume that their use had no bearing on whether or not the guy lived or died and he probably woulda died anyways because documented causes of people with excited delirium have and will continue to die under these circumstances. And what they are saying is true to a certain extent: If people die without it, then why would you expect its use specifically to be the sole cause of their death? This guy in this most recent case most certainly was in a crazed state and very well could have died without the use of the Taser: http://www.cbc.ca/canada/story/2007/11/24/custody-death.html. But that doesn't mean that the use of the Taser even in these cases wasn't contributory in some way. That recent Vancouver airport case had negative toxicology as far as I know, so we can't blame drugs on that guy's death, though he was clearly agitated. But it's just very difficult to prove, even with this video evidence, that the death was caused directly by the taser. It's electrical current. It doesn't leave any pathology.
Two jurisdictions in the States (Ohio and Chicago) have both attempted to certify deaths with "due to Taser" in the death certificate and both have been sued into submission. Taser has a huge lobby and has hired a number of physicists (not doctors) including this guy http://www.andcor.com/page/1/news_032206.jsp to go around the country giving lectures on how Tasers won't cause death and certifying them otherwise will land you a big fat lawsuit.
Anyways, it's a complicated issue, but in reference to your original question, excitation delirium is a state of agitation and occasionally extreme violence and paranoia usually brought on by stimulants and can commonly cause death in a mechanism not yet completely understood. Taser has been using it as an explanation for why people who have been Tasered go on to die for years. Hope that helps. The issue is extremely contentious and and very political at the moment.
To offer another, similar example: police in England tasered a man in a diabetic coma because they thought he was a security threat and he wasn't responding to them. They shocked him because he wasn't responding - he was unconscious - how could that possibly be use of the taser in order protect the officers?