Being charged with a Driving Under the Influence (DUI) offence relating to either drugs or alcohol is stressful, but it can be confusing as well.

Unlike a drink driving charge such as mid range PCA, this offence doesn’t rely on a test, but can come down to what police believe or observe about your driving behaviour. Here is a brief guide to what police need to establish before making an arrest, and potential defences to the charge.


What do the police have to establish before making an arrest?

The offence of Driving under the Influence of Alcohol or Drugs is set out in the Road Transport (Safety and Traffic Management) Act 1999 (NSW).

According to Division 5 of the Act, the police have power to arrest a person if:

  1. The person has failed to submit to, or pass, a sobriety assessment.
  2. The police have a reasonable belief that the person is under the influence of alcohol or drugs.


DUI police arrest powers and court evidence

If the police lay a charge of Driving under the Influence of Alcohol or Drugs, they will generally attempt to present the following evidence at trial:

  • The observations of the police officers and other relevant persons who observed the conduct of the driver.
  • A certificate of the results from the blood or urine test and an analysis as to the nature and quantity of the drug detected.
  • An expert certificate, also known as a pharmacological or toxicology report which comments on the effect of the drug on the person’s ability to drive at the time.

If the police have not acted appropriately in obtaining evidence or otherwise abused their powers, an argument can be made to exclude various items of evidence, without which the prosecution case may fail.

For example, in several matters which have been heard before the courts, the police have arrested a driver and taken them to hospital for a blood or urine test despite not being empowered to do so under the legislation.

In the case of Police v Murray [2011] NSWLC 1, a defendant was successfully able to argue that the analyst certificate and the pharmacology certificate were unlawfully obtained and should therefore be excluded.

The process of forcing a blood sample from a person can be an intrusive procedure and it is for this reason that the police must satisfy themselves of various matters, including the likelihood of a driver’s sobriety, before simply arresting a driver and dragging them to hospital for testing.


Suspicion is not enough

Suspicion that a driver is under the influence of drugs or alcohol does not in and of itself give rise to a power of arrest unless the police can establish that they have in fact undertaken a proper sobriety assessment.

If the police have failed to do so, then a technical defence can be run seeking to exclude the evidence which the police seek to tender on the basis that that evidence was unlawfully, improperly or illegally obtained.


What is a sobriety assessment for DUI?

Frustratingly, neither the Act nor the regulations to the Act define what a “sobriety assessment” is.

In the case of Baulman v The Queen (2007) 6 DCLR (NSW) 1, a driver objected to the fact that the police had failed to conduct a sobriety assessment before arresting him and appealed his conviction.

In that case, His Honour Goldring DCJ stated that “simply making observations which may lead to the formation of a reasonable belief as to the state of a person’s ability as a pre-condition for requiring a person to submit to a sobriety assessment is not, in my view, itself a sobriety assessment.”

It is clear that a formal assessment of a person’s sobriety must take place as a distinct step before the police invoke the power of arrest.

His Honour further held that “I do not presume to suggest what an appropriate procedure would be, but whatever it might have been, it was not followed in this case.” The conviction against the driver was quashed.

It is clear that a conscious process of assessment is required to be undertaken by the police before any power of arrest is invoked – although exactly what this would require is still unclear.


When should police be challenged?

What is inarguable is that the rights of the community should be protected by ensuring that the police adhere to their obligations and requirements.

If the police fail to comply with these obligations then the lawfulness of their actions can and should be challenged in court.


What are the other available defences?

If you have been charged with a DUI offence, there may be certain defences available to you.

You may be able to run a technical defence – this will apply in circumstances where, even though you may have committed the offence, you are able to successfully challenge the admissibility of unlawfully, illegally or improperly obtained evidence.

At Nyman Gibson Miralis, we always give consideration to whether you may have a technical defence available to you, and will give advice as to when that defence can be mounted.

For example, if your licence has been suspended pending finalisation of the charge, it may be possible to argue a technical defence before the matter has been listed for hearing, in an attempt to have your licence returned to you earlier.



Nyman Gibson Miralis provides expert advice and representation in all areas of drink driving and traffic law

Contact us if you require assistance.