So, I just happened to watch this footage on YouTube where some cops in London taze what appears to be a mentally disturbed man with a knife: https://www.youtube.com/watch?v=OFddlI9QHJk
To be honest, I felt a moment of “oh shit” while watching the film because it appears that the mental health guy is on his feet for a couple of seconds after he has been tazed and is waddling towards the officer. In this instance, things went OK, because the guy went down without hurting anyone, but for a moment there, it looked like he was about to get close to the officer while wielding his knife. Maybe he was already being affected by the taser since he was waddling instead of charging. If the guy had had a gun he probably would have had time to fire at least one round.
I haven’t used a taser before but my impression of them was that if the hooks land properly you have immediate incapacitation. In this case, why would that not have happened? Would it have to do with placement of the hooks on the mental health guy? The insulating effect of clothing?