Several Armed Offenders Squad members called to the hostage siege in Opunake last year were reportedly drinking before the fatal shooting.
Anthony Ratahi, 46, was shot dead after he held his former girlfriend Marcelle Beer hostage at gunpoint and barricaded himself inside the Headlands Hotel for 12 hours in July.
Police have revealed to Fairfax Media that 14 AOS members were drinking before the callout. None of them was the officer who fatally shot Ratahi, or the AOS commander and Special Tactics Group commander.
About 60 police officers were called to the siege.
Police said the findings have led to a tightening of their alcohol drinking policies.