One of the hallmarks of a civilised society is strong limits on law enforcement agencies' use of force. In New Zealand, our police cannot beat or shoot you simply because they feel like it. Rather, they can only use force which is reasonable to achieve a lawful purpose, and they have to comply with internal guidelines when doing so. Exceeding those limits is a crime (usually assault), and should result in prosecution.
According to a study by the Campaign Against the Taser, police exceeded the guidelines for the use of tasers in 40% of cases in the recent trial. They are supposed to use them (or threaten to use them) only in cases where suspects are "assaultive" - meaning using or credibly threatening to use physical force. But in 27 of 69 cases where tasers were drawn or used, the victims did not meet that threshold. In 11 of those cases, they were in fact complying with police demands. For their pains, they were threatened with electrocution and torture (three of the 27 were in fact tasered, though it is unclear whether they were "compliant", "passively resisting", or running away. It does not matter; either way, it was outside the guidelines, and an unlawful use of force).
The Crimes Act is very clear: threatening to apply force is assault. The police officers responsible should be facing charges, just like anyone else who threatened to electrocute someone would. They should also be evicted from the force. There should be no place in our police force for thugs who violate the public's trust by using force unlawfully, any more than there should be for rapists.
But apart from the question of holding the police to account, this also makes it clear that our police cannot possibly be entrusted with tasers. The availability of a non-lethal option makes it easy and painless for the police to threaten force, leading to inevitable mission creep and a shift to American-style compliance policing (where the police order people about, and threaten to shoot/beat/tase/pepper spray them if they refuse or do not comply fast enough). And this is not something any of us should want to see in New Zealand. If we want to keep our police under control, and prevent the slide into a swaggering, gun-toting, US-style of policing, then we must scrap the taser.