I think it behooves us to also look at the other side of it, impossible as it may be to properly quantify. How many lives have been saved by the use of Tasers? For instance, without a taser it may indeed be much more likely for cops to have to resort to guns and/or other less predictable violent means to protect themselves. Or, if using the traditional hand-to-hand or club route, there's a much more significant risk of the suspect outmaneuvering the cop and gaining the upper hand, thereby putting him/her in more danger.

I won't argue with the fact that tasers are painful, probably over-used and sometimes lethal, but that's not to say they should be banned. Perhaps more oversight on its use? Like guns (forgive me if i make assumptions here, TV is my only education in this matter), if they are discharged in the line of duty there should be some sort of hoopla, an investigation of some sort and severe punishment if it was found to be used as a first-resort, they would likely be used more cautiously.

Education is also an important factor, it's possible that the cops that have killed with them were not properly educated as to their lethality and would have exercised more caution if they were.