Drink driving:
what reading
is "bad"?

The legal thresholds

For drivers aged 20 and over, there are two thresholds under the Land Transport Act 1998. A breath alcohol concentration (BrAC) of more than 250 but not more than 400 micrograms per litre of breath (mcg/L) — or a blood alcohol concentration (BAC) of more than 50 but not more than 80 milligrams per 100 millilitres of blood — is an infringement offence, dealt with by infringement notice. Above 400 mcg/L (or 80 mg/100ml blood) is a criminal offence prosecuted through the courts. For drivers under 20, the limit is zero — any alcohol is an offence.

Infringement vs criminal charge

If your reading is between 251 and 400 mcg/L (the mid-range), you will typically receive an infringement notice — similar to a speeding ticket — rather than being prosecuted through the courts. This does not result in a criminal conviction, though it does result in demerit points and a fine, and may have other consequences including an immediate licence suspension. If your reading is above 400 mcg/L, you will face a criminal charge in the District Court.

How the reading affects penalties

For a first or second criminal conviction, the maximum penalty is three months' imprisonment or a fine of up to $4,500, with mandatory disqualification of at least six months. For a third or subsequent conviction within five years, the minimum disqualification period increases to more than one year, and the risk of imprisonment increases significantly. In the most serious cases of repeat offending, indefinite disqualification applies.

How the reading affects your options

Your reading is one of the factors the court considers when assessing whether a discharge without conviction is appropriate. A lower reading — just over the 400 mcg/L threshold — is generally viewed as less serious offending than a high reading, and may make a discharge application more realistic. A very high reading does not automatically preclude a discharge, but it makes the threshold harder to meet. The other circumstances — your driving, whether there was an accident, your personal circumstances — all matter.

Challenging the evidential breath test

Evidential breath testing devices must be certified and properly maintained, and the testing procedure must be followed correctly under the Land Transport Act. If the device was not properly maintained, the procedure was not followed, or there is some other issue with the taking of the evidential test, the result may be challengeable. Sam examines this in every drink driving matter.

The key point

Your reading matters — but it is only one part of the picture. The overall outcome of a drink driving charge depends on how the case is handled, what options are pursued, and how the matter is presented to the court. Do not assume that because your reading was high, there is nothing to be done — or that because it was low, a conviction is inevitable.