Breath test at 300 mcg/L plus prescribed codeine
At 9:30 pm a 22-year-old full licence holder is stopped at a police checkpoint. They drank three 500 ml bottles of 7% beer between 5:30 pm and 7:30 pm. At 5:00 pm they also took a prescribed codeine tablet for back pain; the label says it may cause drowsiness and that they should not drive or use machinery until they know how it affects them. They feel 'completely normal'. The breath screening test is positive. The evidential breath test reads 300 micrograms of alcohol per litre of breath. They say they stopped drinking two hours ago, have had a large coffee, and that the codeine is prescribed so 'it doesn't count'.
1. Is the driver over the legal alcohol limit, and what is the significance of 300 mcg/L? What about the codeine?
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For a driver aged 20 or over, the legal breath alcohol limit is 250 micrograms per litre of breath. A result of 300 mcg/L is above that limit, so the driver is over the adult limit. The 251-400 mcg/L band is generally treated as an infringement offence rather than the higher criminal band, but it is still an offence and carries demerit points and a fine. The codeine is a separate issue. Being prescribed does not make it legal to drive while impaired. The label warns of drowsiness, and if the codeine makes the driver unable to drive properly, they can be charged with driving while impaired by a drug. Alcohol and codeine can both depress the central nervous system, so the combination may impair judgement and reaction time even if the driver feels normal.
2. Does coffee or waiting two hours make it safe to drive home? Explain how alcohol is eliminated.
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No. Alcohol is eliminated mainly by the liver at roughly one standard drink per hour, and that rate varies with the person, food, body size and other factors. Coffee, food, water, fresh air and a shower do not speed up elimination. Waiting two hours helps, but it does not mean the driver is under the limit now. At 300 mcg/L at 9:30 pm, they may still be over the limit for some time. The codeine adds sedation and slows reaction time, so the combined effect is worse than alcohol alone. The safe and lawful decision is not to drive. They should arrange a sober driver, a taxi or rideshare, or wait much longer and retest before driving, and they should not rely on feeling normal.
3. What should the driver do next, and what could happen to their licence?
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The driver should cooperate with the checkpoint, provide the evidential breath test as required, and not attempt to drive away. They should tell police about the codeine, because the label warning and the combination with alcohol are relevant to impairment. They should arrange alternative transport home. On the licence side, an excess breath alcohol infringement carries demerit points; if the driver reaches 100 demerit points in two years, they can be suspended. If police consider the codeine impaired their driving, they could face a drug-impaired driving charge, which can lead to court, a fine, disqualification or imprisonment. Insurance may also be affected. The key judgement is that a prescription label and a coffee do not make the driver fit to drive.