Tasers are rarely, if ever, the cause of death. Most of the cases involving the death of someone that has been tased are in fact due to cocaine overdoses and 'excited delirium'. As usual, the media reports of deaths have largely been unsubstantiated and border on hysteria. Why should a reporter check the facts when he/she can blame a cop for a death in custody? - That makes for a much better story!
The amperage from a taser is so low that it won't even interefere with an implantable cardiac defibrillator and if it can't do that then it can't initiate a toxic heart rhythm. See
http://www.taser.com/documents/PACE_Dr_McDaniel_Rpt.pdf]
In custody deaths have been attributed to mace, pepper spray, and other 'less lethal' means of restraint and submission. In virtually all of these cases the deaths are due to 'excited delirium' -
http://www.laaw.com/sed_art.htm, the BG is already coked up, his adrenaline has peaked, he has physically exhausted himself from resisting, and his heart just can't take it anymore - he dies. In the course of the struggle he may have been tased, sprayed or whatever and then the cop gets blamed for 'innapropriate' actions when he probably would have been justified, and maybe better off, in just having shot the bg and getting it over with.
Anyway, sorry for the diatribe, there is just a lot of misinformation being spread by the media and bleeding hearts on this topic and I just hate sitting by while it propagates!
All that being said, if a BG is pointing a taser at me or mine, I'm not hesitating to draw and shoot because I'll damn well know his intentions aren't exactly good!