Tasers were introduced in 1969 as an alternative to the use of deadly force. Their use was to be considered only in situations where, until this point, the officers would have had to fire their sidearm. In other words, the Taser was designed as an alternative to a bullet: Far less permanent, far less frequently deadly. But, in its initial roll-out, the device was to be used ONLY as an alternative to deadly force. If the officer's life was in imminent danger, or the life of an innocent was in danger, the device would be used to provide a non-lethal resolution to the threat, as opposed to shooting and possibly killing the suspect.
In the nearly 40 years since, the Taser has gained popularity and profile amongst law enforcement as a compliance tool. Instead of "correcting a suspect's behaviour" with the baton, you tase him. Quick and effective, right? If he won't listen, settle down, allow you to cuff him, or is in any way resisting or trying to get away, you shock him. It works 99% of the time, which is more than can be said for batons (too hard to get a good back-swing) and pepper-spray (messy, and you might get some on yourself).
The problem has become that cops today are too reliant on the device. They use it not to avoid killing a suspect, as originally intended, but to elicit compliance. They police are under-staffed, stretched too thin, and they lack the time (or, in some instances, ability) to reason with a suspect, to calm them down, to explain what is going on, or wait for an interpreter. There's going to be another emergency call in 10 minutes, so they tase him, take him back to the station, and head off to the next call.
One needs only to watch "Cops" to see this proclivity towards "compliance at all costs" on the part of law enforcement today. If he won't let you cuff him, you tase him. If he won't get out of the car, you tase him. If he runs, don't chase him - tase him.
The RCMP in Vancouver should not have used the Taser in their situation. Unless the "suspect" (who did not speak English) indicated he had a bomb strapped to him, there was no reason that the 4 (!) of them could not have wrestled him to the ground if he became threatening. There is no way that any of those officers can say he felt his life or the life of a bystander was in danger, so there was no need to deploy the Taser.
The bigger question that we, as a society, have to answer is whether or not Tasers should be used by our police forces at all. The more accustomed to using them that our police become, the more they find they HAVE to use them, as old-school policing and the associated skill set (negotiation, scene control, etc.) fall victim to the need to clear scenes as quickly as possible due to manpower shortages. In a world where our police had the resources, training and manpower to do their jobs properly, Tasers would only be used for their original purpose: Instead of shooting and possibly killing someone who is trying to kill them, the officers would use the Taser.
Tasers can and do kill people, and the police use them far too often. But, on the whole, Tasers are a lot less lethal than the bullets they were meant to replace. They should NOT be used to guarantee compliance with police, or to stop people from running or resisting - they should be used to stop people from killing. There's a BIG drop-off there.
If my friend won't let the police cuff him for an overdue parking ticket, I don't want him tased. But if he gets drunk and lunges towards an officer, I'd rather have him "ride the lightning" at 50,000 volts than catch a bullet. My take? Keep the Tasers as a non-lethal option, increase the number of officers on the streets, and make sure that you spend 10 times as much effort on teaching officers to reason with suspects as you do Taser, pepper spray and proper baton technique.