A criminologist says it's important for Police taser-use not to become the norm.

The Independent Police Conduct Authority found police unjustifiably tasered a man in the back in Auckland.

The man was pulled over for speeding on his motorbike, but was tasered when he tried to run away.

He suffered facial injuries and was knocked unconscious when he hit the ground.

Criminologist Trevor Bradley told Chris Lynch it's police can only use tasers when people are under threat.

"The concern that we have there is taser use becomes something of a default position rather than as a last resort."

LISTEN TO TREVOR BRADLEY TALK WITH CHRIS LYNCH ABOVE