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DUI — driving under the influence

DUI is the charge for being too impaired to drive safely — and the thing that sets it apart is that police don't need a number. Unlike a PCA (drink-driving) charge, which rests on a breath reading, DUI is based on how you seemed: erratic driving, slurred speech, unsteady movement, a failed sobriety test, or being found slumped behind the wheel. That's why it's the go-to charge for drug impairment, or when no reading is available. You can even be charged without driving — sitting in control of the car, engine running, is enough. Because it's judged on observation rather than a number, it's both more serious in some states and more open to challenge.

The whole idea in one picture

Judged on how you seem, not a number

DUI doesn't rely on a breath reading. It's built on what police observe — which is why it covers drug impairment, and why even sitting in a parked car can be enough.

1 · Impaired erratic · unsteady 2 · No reading needed not based on a number 3 · Even if parked in control is enough 4 · Penalties jail · disqualification

DUI vs PCA — the key difference

They both deal with driving while affected, but they prove it in completely different ways:

PCA — by the number

  • Based on a measured breath reading (your BAC)
  • The reading decides the range and penalty
  • Used for standard drink-driving cases

DUI — by impairment

  • Based on how you seemed, not a reading
  • Used for drug impairment, or when no test is available
  • Carries heavier maximums in some states
No reading required. Police can charge DUI purely on observations — erratic driving, slurred speech, an unsteady walk, a failed sobriety test, or being found slumped at the wheel. That's exactly why it's the usual charge when drugs are involved, or when someone refuses or can't provide a sample.

What police rely on

Because there's no number, the case is built from what was seen and recorded:

The evidence

  • Observations of dangerous or erratic driving
  • A collision or serious incident
  • A failed or refused roadside test
  • Bodycam footage, witnesses, toxicology reports

You don't have to be driving

  • Being in control of the vehicle can be enough
  • Sitting in the driver's seat with the engine running
  • Found slumped or impaired behind the wheel
Choose your state

Penalties where you are

New South Wales

NSW
Most serious cases — top of the scale
Up to 18 months in jail (first offence)

Plus a fine of up to $3,300. Second offences, or where someone is injured, are treated far more seriously.

Read this as a ceiling, not a forecast. The maximums are for the worst cases. But because a conviction almost always carries a mandatory disqualification, even a first DUI means real time off the road.
Licence disqualification

Also expect

Common defences

Because DUI rests on observation rather than a number, the case is often genuinely arguable:

You weren't in control

You weren't driving or in charge of the vehicle.

A medical condition

Symptoms mistaken for intoxication had a medical cause.

Involuntary intoxication

You unknowingly consumed a substance — for example, a spiked drink.

Not enough proof

The evidence doesn't establish impairment beyond reasonable doubt.

More traffic offences

Traffic overview → PCA charges → Drink & drug driving → Negligent, reckless & dangerous driving → Driving suspended or disqualified → Penalties & disqualification →

Charged with DUI? It's worth challenging.

A DUI rests on what police observed — which makes the evidence, the procedure, and whether you were in control all genuinely arguable. We can point you to traffic lawyers in your state.

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This is general information, not legal advice

This page explains how these charges generally work — it can't tell you what will happen in your case. DUI laws, penalties and disqualification periods vary by state and territory. If you've been charged, talk to a traffic lawyer before your court date — early advice can affect the outcome.

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While we don’t provide legal advice—as every case is unique and only a qualified lawyer is permitted to do so—we’ll do our best to guide you with relevant general information. If we’re unable to assist, we can refer your query to a criminal lawyer.