Challenging Breath Test Results in NSW Courts: What You Need to Know

Why Breath Test Challenges Matter

Being charged with drink driving in NSW can have serious consequences: heavy fines, licence disqualification, interlock device orders, and even imprisonment for repeat or high-range offences. For many, a conviction can affect employment, travel, and personal reputation.

Because breath test results are often considered “scientific evidence,” many drivers assume they cannot be challenged. In reality, NSW courts have recognised that breath test results are not infallible. If your test was conducted incorrectly, influenced by medical conditions, or if there are doubts about accuracy, you may have valid grounds for defence.

At LY Lawyers, our experienced drink driving lawyers have successfully defended clients by challenging breath analysis evidence. Below, we explain how breath testing works, why errors happen, and what legal avenues may be open to you.

How Breath Testing Works in NSW

NSW Police conduct two types of alcohol testing:

• Preliminary roadside breath tests (RBTs): A quick test using a handheld device to detect alcohol. The result is not admissible in court—it is only used to determine whether you should undergo a formal test.
• Evidentiary breath analysis: If the RBT is positive, you’ll be taken to a police station or mobile testing unit for a second, more accurate test on an approved machine. This is the reading used in court.

The Prescribed Concentration of Alcohol (PCA) offence categories under the Road Transport Act 2013 (NSW) are:

• Novice Range: 0.00–0.019 (applies to learner, provisional, and special licence holders)
• Special Range: 0.02–0.049
• Low Range PCA: 0.05–0.079
• Mid Range PCA: 0.08–0.149
• High Range PCA: 0.15 and above

(NSW Legislation – Road Transport Act 2013)

When Can Breath Test Results Be Challenged?

• Medical Conditions and “Mouth Alcohol”

Conditions such as acid reflux, regurgitation, asthma inhalers, or vomiting can cause “mouth alcohol,” where alcohol vapours remain in the mouth and lungs rather than representing actual blood alcohol levels.

Case example: In 2024, a Sydney mother was charged with high-range PCA after recording 0.193. Her lawyer successfully argued that her recent consumption of liquid chlorophyll (which contained alcohol) combined with reflux had falsely inflated her reading. The court dismissed the charge because there was reasonable doubt about her actual blood alcohol concentration.

• Device Malfunction or Calibration Errors

Evidentiary breath analysis machines must be regularly maintained and calibrated. If records show lapses in servicing, or if an officer cannot prove proper operation, the result may be unreliable. Although rare, such arguments can form part of a defence strategy.

• Police Procedure Mistakes

NSW Police must comply with strict procedures under the Road Transport (General) Act 2005. For example:

• A breath test must occur within two hours of driving.
• If a person is unable to provide a breath sample due to medical reasons, police should arrange a blood test instead.
• Officers must ensure a 15-minute waiting period if the driver has vomited, regurgitated, or consumed anything before the test.

Failure to follow procedure can make the result inadmissible.

• Requesting a Blood Test

If you believe your reading is wrong, you may request an independent blood test, usually within two hours of the alleged offence. A discrepancy between the breath and blood results can support your defence.

Legal Strategies to Defend a Breath Test Result

At LY Lawyers, our approach to drink driving defence is tailored to each client. Typical strategies include:

1. Examining Evidence Thoroughly
   • Police records, machine calibration logs, and body-worn camera footage.
   • Statements from witnesses about what you ate, drank, or your medical condition.
2. Engaging Expert Witnesses
   • Forensic toxicologists can model how alcohol metabolises in your system, potentially proving your BAC was lower at the time of driving.
3. Highlighting Reasonable Doubt
   • Courts do not need to be convinced of innocence—only that there is reasonable doubt. Demonstrating uncertainty about machine accuracy or procedure can result in acquittal.
4. Negotiating Charge Reductions
   • If challenging the evidence completely is not viable, lawyers may negotiate to reduce a high-range PCA to a mid-range offence, significantly lowering penalties.

What Happens If You’re Convicted Anyway?

Even if a challenge is unsuccessful, an experienced lawyer may still:

• Argue for a Conditional Release Order (CRO) without conviction (formerly known as a “Section 10”).
• Seek to minimise penalties, such as shorter disqualification periods or avoiding an interlock order.
• Present strong character references and evidence of rehabilitation (e.g., completion of the Traffic Offender Program).

Learn more about Drink Driving Penalties in NSW on our website.

FAQs About Challenging Breath Test Results

Q1: Can I refuse a breath test in NSW?
No. Refusing a breath test is an offence with penalties similar to high-range PCA.

Q2: Is a blood test more accurate than a breath test?
Yes. Blood tests directly measure alcohol in the bloodstream, while breath analysis is an estimate. Courts generally prefer blood test evidence when available.

Q3: How long do I have to request a blood test?
You generally need to request it within two hours of being stopped, otherwise the result may not be admissible.

Q4: Can a lawyer get my drink driving charge dropped?
It depends on your circumstances. A lawyer can identify weaknesses in the prosecution’s evidence and either have charges dismissed or negotiate a less serious penalty.

Why Choose LY Lawyers to Defend a Drink Driving Charge?

• Specialist Experience: Our team has decades of combined experience in criminal and traffic law, including complex drink driving defences.
• Proven Results: We have successfully defended cases where breath test evidence was found unreliable.
• 24/7 Availability: Drink driving arrests often happen late at night—we are available around the clock to advise.
• Client-Focused Strategy: Every case is handled with a personalised plan designed to achieve the best possible outcome.

Read more information in our Drink Driving Offences.

Challenging breath test results in NSW is not easy—but it is possible. Whether the issue is medical conditions, machine errors, or police procedure, having an experienced legal team can make all the difference.

If you’ve been charged with drink driving, don’t assume the result is final. Contact LY Lawyers today for expert advice and a strong defence.