Honest and Reasonable Mistake Information

What does an honest and reasonable mistake of fact mean?

In plain English, an honest and reasonable mistake of fact is a possible legal excuse or justification raised in some driving cases. It concerns whether a person honestly believed a relevant fact existed, and whether that belief was reasonable in the circumstances. The issue is assessed under the law applying to the particular charge, the wording of the allegation and the evidence available. It is not a general rule that excuses every drink-driving or drug-driving allegation.

This concept is different from simply disputing an element of the prosecution case. A dispute may concern whether the prosecution can prove the required conduct or circumstance at all. A legal excuse, by contrast, may accept that the conduct is alleged but raise a recognised legal issue about the person’s state of belief. The distinction matters because the applicable test depends on the charge and the law in force at the relevant time.

Why strict-liability treatment can matter

Many driving offences are described as strict-liability offences. Legal Aid NSW explains this at a high level as meaning that the prosecution generally must prove the conduct and relevant circumstances, but does not usually have to prove that the person intended to break the law. Its example is a mid-range prescribed concentration of alcohol allegation, where the prosecution must establish driving, or an attempt to drive, and the specified blood-alcohol range.

That does not mean every DUI, PCA or drug-driving offence is treated identically, or that an honest and reasonable mistake issue will be available in every matter. The current NSW Road Transport Act 2013 includes provisions concerning prescribed concentrations of alcohol and the presence of certain drugs, but the exact section, charge classification and applicable provisions must be checked against the current in-force legislation. Amendments, commencement dates, evidentiary rules and procedure can change.

What is assessed in a general review?

A factual mistake issue is not decided by a label alone. A general review may need to identify the precise charge, the facts relied on by the prosecution and the fact said to have been misunderstood. It may also consider whether the evidence could support an honest and reasonable belief about that fact under the law applying to the allegation.

Relevant material can depend on the issue. For example, contemporaneous records or witness evidence may be relevant in some circumstances, but their significance cannot be determined without examining the charge, admissibility questions and the rest of the prosecution case. A checklist is therefore a starting point for organising information, not a conclusion that a legal excuse exists.

• Record the exact wording of the charge and the date alleged.
• Keep the Court Attendance Notice and any accompanying documents together.
• Identify, in neutral terms, the fact that is said to have been misunderstood.
• Preserve contemporaneous documents and identify potential witnesses without altering or embellishing the material.
• Note the listed court, date and plea information, and check current Local Court instructions.
• Obtain advice before deciding whether to plead guilty or not guilty.

Is it an automatic defence to drink driving?

No. An honest and reasonable mistake of fact is not an automatic defence to a drink-driving charge. Whether the issue is legally available, and whether the evidence could establish it, depends on the particular allegation and the law applying to it. This page does not say that a charge will be dismissed, that a person will be acquitted, or that an alleged mistake will reduce a sentence.

A person should not decide to plead guilty or not guilty solely because this topic appears relevant. In Local Court traffic matters, disputing an alleged offence generally leads to a later hearing rather than finalisation on the first listing, and attendance may be required. The Local Court explains that criminal cases are proved beyond reasonable doubt and that a not-guilty plea is ordinarily dealt with through a hearing or preparation for one.

Current-law and historical-status warning

Information only: This page is general information, not legal advice, and it cannot assess an individual charge or recommend a plea. The current NSW legislation page identifies the Road Transport Act 2013 version as in force from 10 June 2026. That status, charge wording, offence classification, evidentiary rules and court procedures must be rechecked before publication and before reliance. Historical Road Transport Act versions, legacy drink-driving schemes and duplicate or older pages must not be treated as current law.

The practical effect of any issue may also depend on the offence date, the charge document, prior driving history and the evidence admitted at hearing. Court staff can explain procedures and provide listing or file information, but they cannot give legal advice, advise what to say or predict an outcome.

Frequently asked questions

Official sources

For current source material, check the Road Transport Act 2013 (NSW), the Legal Aid NSW driving-offences overview, the NSW Local Court driving and traffic guidance and the NSW Local Court criminal-jurisdiction guidance. Check publication and amendment dates before relying on time-sensitive information.