Honest and Reasonable Mistake

Honest and Reasonable Mistake

Our lawyers have used the ‘honest and reasonable mistake’ defence over the years to have many clients found ‘not guilty’ to a range of offences. It is also known as Proudman v Dayman defence (Proudman v Dayman (1941) HCA 28).

This defence only applies to certain offences, so it is important that an accredited specialist criminal lawyer handles your case.

If you believe that this defence may apply to you, contact us immediately to speak to our team.

What is an Honest and Reasonable Mistake defence?

This defence can be used if you honestly believed that you were acting lawfully, and if you knew your actions were a crime, you would not have acted in that way.

This defence is often used in traffic cases.

When Can You Use an Honest and Reasonable Mistake Defence?

You can only use an ‘honest and reasonable mistake’ defence if you a charged with a ‘strict liability’ offence.

What Is a ‘Strict Liability’ Offence?

A strict liability offence is an offence that does not require the prosecution to prove the ‘mens rea’ of the offence. This means that even if you do not have the intent to commit the offence, you can still be found ‘guilty’.

How do you prove an Honest and Reasonable Mistake defence?

You must prove on the balance of probabilities (ie. more likely than not) that:

1. You held a belief about a fact

The belief you held must relate to a fact, not the law. For example, if you held an incorrect belief about what the speed limit was, then this is a belief as to the law.

However, if you held an incorrect belief as to the speed you were travelling, then this is an honest and reasonable mistake of fact.

2. You held an honest belief

This is quite straightforward. You can satisfy this element by giving evidence as to your belief. Provided there is no evidence to the contrary, you should be able to fulfil this criterion.

An example may be if you held an honest belief that you were travelling below the speed limit, but due to issues with your speedometer, you were in fact travelling over the limit.

3. The belief was ‘reasonable’

This is often the most difficult part of this defence. The Court will decide whether your belief was ‘reasonable’ by hypothetically assessing whether an ordinary person in your circumstances would have held the belief.

Importantly, the Court will look at what steps you took in establishing your belief. Following on from the above example, if your speedometer was incorrect, but you had not serviced your vehicle in a number of years, then this belief may not be reasonable.

However, if your vehicle had been serviced at a reasonable time prior to the incident, then your belief that the speedometer was correct will be reasonable.

If you did not take any steps, then it is likely that the Court will assess your actions as ‘unreasonable’ and find the defence has not been made out.

Examples of the Honest and Reasonable Mistake Defence

Some examples of this defence being successful include:

1. If charged with driving disqualified: you believed you could drive because the Roads and Maritime Service (RMS) informed you of the incorrect date you could drive again;
2. If charged with speeding: If you believed you were travelling below the speed limit but your speedometer was incorrect, and your vehicle had been appropriately serviced;
3. If charged with a prohibited drug offence: you believed that the drug was a legal substance;
4. If charged with a sexual offence: you believed that you had consent (CTM v the Queen [2008] HCA 25).

Each case will ultimately turn on its own facts. If you believe that tis defence may apply to you, contact our team to arrange an initial consultation.

Honest and reasonable mistake defences take significant preparation. We will usually need to anticipate what arguments the prosecution will make to say that your belief was not honest and reasonable.

That is why you should contact us now to speak to an experienced criminal defence lawyer.