Police will waive about 80 drink-driving convictions and tickets after a calibration problem with one model of the breath-testing device they use.
National manager road policing Superintendent Steve Greally said 400 Drager 7510 devices were rolled out during July to one, two and three-person stations in mostly rural areas.
All had been recalled, and 49 of the 343 tested had failed to give an accurate reading.
"It's a very concerning thing, of course, when you don't understand why," he told Checkpoint.
"Until we understand why, they are not going to be used at all. We need to make sure the devices are working well and can be relied upon in court."
The devices had failed by only a small margin but, for the avoidance of any doubt, the police had decided to waive any infringements or charges which had have resulted from them.
"Those in this bracket should therefore consider themselves very lucky to have avoided police action in this instance," he said.
"This means that if it emerges that anyone has been ticketed or prosecuted incorrectly as a result of this problem, the action will be withdrawn by police."
Work was under way to identify the individual circumstances of each of the about 80 positive evidential breath tests identified as being caught by the machines - a number Mr Greally described as small in the context of the about 21,000 alcohol-related offences recorded by police in the past year.
The problem emerged during a recent random spot test by police, and they had been sent for further testing as a "precautionary" measure, he said.
Police would continue to test drivers as usual with their other 2900 other alcohol-testing devices.
"Operationally, there will be no change to our continued enforcement of drink drive offences, as testing machines in booze buses and stations are unaffected. This means anyone caught driving while impaired can expect to be dealt with in the same way," Mr Greally said.
Police would contact anyone whose ticket or conviction would be waived as a result of the error, he said.
The president of the criminal bar association, Tony Bouchier, said the people affected by the error could have incurred significant financial cost, and should seek legal advice about compensation.
"The people who have been charged with drink driving as a result of this faulty technology, in some cases they have been taken off the road for 28 days and incurred huge costs there, and the trauma of that. They've been detained by the police for a period of time when they should have been going about their lawful business. And I guess a number of them have spent money on lawyers to get legal advice."
Mr Bouchier said the justice system relied on the breathalyser technology being accurate.
