The Defence of Honest and Reasonable Mistake of Fact

What Is The Defence Of Honest And Reasonable Mistake Of Fact?


What charges can I use the defence of Honest and Reasonable Mistake of Fact?


A large number of traffic offences, including Speeding, Drink Driving, and Drive Whilst Suspended or Disqualified are offences that are considered as “strict liability” offences.

The defence of “Honest and reasonable mistake of fact” applies to offences of ‘Strict Liability’. When prosecuting an offence of Strict Liability it is not necessary for the prosecution to prove any mental element; proof of the act alone is sufficient to constitute a crime.

The leading case that sets out this common law principle is Proudman v Dayman [1941] HCA 28; 67 CLR 536, a long standing High Court of Australia case.

There is a defence of honest and reasonable mistake of fact to these offences. That is, that the person was honestly mistaken as to certain facts existing but had a reasonable belief about those facts and had those facts existed, the conduct would not have constituted an offence.

Put it simply, if you had an honest belief that you were not committing the offence, and the court also finds that it is a reasonable belief, you may be found “not guilty” of the offence.

Here at LY Lawyers, we have encountered countless situations where the defence of Honest and reasonable mistake of fact was applicable, from serious offences of importing prohibited goods, to trivial traffic matters.


An example:


A good example of this is driving whilst suspended. If a person has not has not paid fines the Roads and Traffic Authority may suspend their licence. Usually the RTA will send out a letter informing the person of the suspension. If a person has not physically received a letter and did not know that their licence was in fact suspended the defence of reasonable mistake of fact would arise. Generally, the court will then consider two questions: 1. Did the defendant honestly make a mistake about the status of his/her licence, and if so, 2. Was it a reasonable mistake?

Another example, is drink driving. Did you honestly think that you were not over the limit? Was it reasonable in the circumstances for you to have that belief?

Once raised by the defence by identifying some evidence that supports the assertion, in the example given by saying ‘I did not receive a letter telling me that I was suspended’ it is for the prosecution to disprove the defence and that the person did not hold this belief.

It is quite remarkable how many clients we encounter everyday who do not know their rights, and the defences they have to generally challenge traffic offences based on an “honest and reasonable mistake of fact”

For more information on the defence of honest and reasonable mistake of fact, and to see case studies where we have been successful, go to:


If you are charged with any offence you must get professional advice on the evidence against you and any defences that may be available.


Call LY Lawyers on 1300 595 299 for a free consultation with one of our traffic lawyers.