Before outlining the honest and reasonable mistake of fact defence, it is important to get a general understanding of ‘absolute liability offences’ and ‘strict liability offences’.

Absolute Liability Offences

An absolute liability offence is any offence which there is no requirement to have a guilty mind (‘mens rea’) at the time of committing the offending conduct. All that is required to be established for an absolute liability offence is the act constituting the offence (‘actus reus’).

‘mens rea’ can include an intention to do the offending actions, knowledge or recklessness as to the consequence of his/her offending conduct at the time of doing it, wilful blindness.

For absolute liability offences, the honest and reasonable defence does not apply. An absolute liability offence will be made out simply by proving that the acts constituting the offence occurred- usually in regulatory type offences.

Strict Liability Offences

A strict liability offence is any offence where there is also no requirement to have a guilty mind (‘mens rea’). This type of offence will be proven by establishing the offending conduct. But the defence of honest and reasonable mistake of fact applies to these types of offences.

Examples of strict liability offences include speeding and drink driving offences. Common defences to these types of offences are the honest and reasonable mistake of fact defence which is outlined in the popular case of Proudman v Dayman.

What is ‘Mens Rea’?

‘Mens rea’ is a principle that requires there to be an evil intention, or a knowledge of the wrongness of an act as an essential element in an offence. It’s based on the idea that “the essence of the principle of mens rea is that criminal liability should be imposed only on persons who are sufficiently aware of what they are doing, and of the consequences it may have, that they can fairly be said to have chosen the behaviour and consequences.” (Professors Andrew Ashworth and Jeremy Horder).

The Case of Proudman v Dayman [1941] HCA 28 and the Honest and Reasonable Mistake of Fact Defence

This involved the defendant who was charged for allowing an unlicensed driver drive the car. The defendant argued that, although mistaken, he held an innocent (honest) belief that the driver had a licence which was valid, and that this belief was held on reasonable grounds- which if true would mean he was not guilty.

This case establishes that for strict liability offences, such as drink driving and speeding offences, an accused person will be ‘not guilty’ if he/she held an honest and reasonable belief (although a mistaken belief) in a state of facts which , if they existed, would have made the accused person’s act innocent.

In practice, if you are wanting to use this defence, as the person accused you are required to raise the defence into evidence (to prove it on the balance of probabilities), which requires giving evidence to establish that you held a certain belief (although a mistaken belief) as to facts which if it was true would mean that you didn’t commit the offence even though you were mistaken as to that, so long as that belief was held on reasonable grounds.

This defence only applies to mistakes as to facts, not as to law. This means that the honest and reasonable mistake defence will not apply if you made a mistaken but honest belief as to the law on reasonable grounds.

In determining whether the belief was held on reasonable grounds, the court will look into the circumstances to assess whether a reasonable person in your shoes in those circumstances would have held the same belief. If yes, you will succeed, but if no, you will fail in this defence.

Once the defence is sufficiently raised by you as the defendant, the prosecution is required to disprove beyond reasonable doubt either one of the following two elements of this defence:

  • Although you were in fact mistaken, you honestly held that belief; or
  • That belief you held was held on reasonable grounds.

If the police prove that your belief was not held on reasonable grounds given the circumstances, then you will be guilty of the offence. This is an objective test, while the first test is a subjective test.

The subjective test is harder to disprove than the objective test for obvious reasons, however, the prosecution can end up disproving that subjective test- where the court can draw inferences from the evidence that can lead it to find that the accused person didn’t honestly hold that belief- this is where cross examination can be critical in a hearing.

Driving Under the Influence (DUI) Charges

Driving on a NSW road whilst being under the influence of alcohol or drugs carries heavy penalties with a criminal conviction under section 112 of the Road Transport Act (NSW).

A person guilty of DUI will face a fine of up to $3,300 and/or up to 18 months imprisonment. He/she will also face an automatic disqualification period of 3-years or a discretionary minimum of 12-months.

The above penalties will apply unless you get a non-conviction as a penalty under section 10 dismissal or conditional release order without conviction- in which case you will not have your licence disqualified, and you will not received a criminal conviction or lose any demerit points. Nor will there be a fine imposed in that event.

You can only be guilty of DUI if you drive or occupy the seat of a vehicle attempting to turn it on while being under the influence of drugs or alcohol at the time.

The honest and reasonable mistake of fact defence can apply to a DUI offence if:

  • You mistakenly but honestly believed to not be under the influence of alcohol to such an extent as to be incapable of having proper control of the vehicle; and
  • You held that belief on reasonable grounds.

You will fail at this defence if for example, your alcohol reading was very high ie 0.265 for the court to conclude that you must have felt intoxicated; you were driving erratically; you knew that you had consumed a substantial amount of drinks before driving.

On the other hand, you will likely succeed in this defence if someone had secretly drugged your last drink without your knowledge just before getting behind the wheel, which then caused you to hold an honest bust mistaken belief that you were intoxicated, and in circumstances you were unaware, it was reasonable for you to have held that belief given your drink was spiked without your knowledge or suspicion.

Speeding Offences

The honest and reasonable mistake of fact defence can also apply to a speeding offence.

This defence will more likely succeed if you drive a vehicle at 100km/h on a 90km/h zone of road with a faulty speedometer which incorrectly depicts your speed at 90km/h, and in circumstances you were unaware that the speedometer of the vehicle was faulty.

However, if you were aware that the speedometer of the vehicle was faulty but drove it anyway, then you will likely fail in this defence for obvious reasons.

The honest and reasonable mistake of fact defence can also apply to sexual assault offences and indecent assault offences in NSW.


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Published on 29/11/2018

AUTHOR Jimmy Singh

Mr. Jimmy Singh is the Principal Lawyer at Criminal Defence Lawyers Australia - Leading Criminal Lawyers in Sydney, Delivering Exceptional Results in all Australian Criminal Courts.

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