Two Ashburton police officers have been cleared of planting evidence by placing a man's wallet in a bag containing drugs.
An Independent Police Conduct Authority report said it was unlikely the two officers planted the evidence but found lapses in good practices created a situation where it was difficult for them to corroborate their version of events.
The officers searched the car of a man in 2017 and found a bag containing drugs, for which he was charged.
At his trial the man said the bag was not his and had been planted by the police, which the officers denied.
The judge was critical of the officers' evidence and dismissed the charge.
The authority found the officers did not correctly follow police procedures when they arrested the man and seized the bag, but that the accused's evidence about what happened at the police station was unreliable.
The authority's general manager, Warren Young, said the officers put themselves in a position where their integrity was publicly called into question.