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You’ve probably heard the saying, “ignorance of the law is not an excuse”. Well, in very limited circumstances it can be. In Proudman v Dayman Dixon J summarised the defence of honest and reasonable mistake of fact:

“As a general rule an honest and reasonable belief in a state of facts which, if they existed, would make the defendants act innocent affords an excuse for doing what would otherwise be an offence.”

Proudman v Dayman [1941] HCA 28

The law recognises that sometimes a person commits an offence because of an honestly and reasonably held belief that they were not doing anything wrong. These people should not be convicted.

A fishy defence?

The most famous case involving the honest and reasonable mistake defence is that of Western Australian lobster fisherman, Jeffrey Palmer. Mr Palmer went to the local fisheries office to find out exactly where he could put his lobster pots. Based on that information he went fishing in an area he believed he was allowed to fish. It turned out that he was fishing in a prohibited area and he was charged. Mr Palmer pointed to the information he’d received from the information from the fisheries office. Based on that he honestly and reasonably believed that he could fish there.

The matter went all the way to the High Court and ultimately Mr Palmer lost. The accepted that his belief was certainly honest and reasonable. However he was mistaken about the law not a fact. In covering the story the Sydney Morning Herald appropriately titled the story, “Between a rock lobster and a heartless place”.

Proving an honest and reasonable mistake of fact

The defendant, or person charged, needs to raise the defence “on the balance of probabilities”. You need to show that it’s more probable than not that you believed that you were not committing any offence at all.  In practical terms this is usually done by giving evidence in court. In some cases you can ask the court to have regard to anything you said to the police.

The onus then shifts to the prosecution who must rebut the defence beyond a reasonable doubt if they are to succeed. Usually this is done through cross examination or questioning. The prosecution will attempt to persuade the court that your belief was not honest or reasonable or they may argue that it is a mistake of law.

Three elements of the defence

The defence of an “honest and reasonable mistake of fact” relies on three elements.

The belief must be honest

In most cases, a defendant proving to the Court that their belief was honest is quite simple. Unless there is evidence to show they didn’t really believe in a certain state of facts it is usually just a matter of the defendant giving that evidence. This can be either in court or a defendant can ask the court to take any responses they gave to police questioning into account.   

The belief must be reasonable

What is often harder to prove, is that the mistake of fact was also reasonable. Whether a belief is reasonable or not is determined by a court. The court will often take into account the source of the information / belief, what you relied upon, and whether you made any enquiries of your own. The court then determines if it was objectively fair, rational or logical for you to have that belief at the time.

A mistake of fact not law

One of the most commonly misunderstood aspects is that you must be mistaken about a fact and not mistaken about the law. Not knowing that something is illegal, or not realising what you are doing is not a defence. You need to satisfy the court that you believed in a fact which if true, would mean that you were not committing an offence. The difference is best illustrated by the examples below.

Examples of an honest and reasonable mistake

Speeding

The defence of honest and reasonable mistake is often incorrectly relied upon in speeding matters. The applicable speed limit for any particular road is a matter of law. So telling a court that you thought it was a different speed limit is not a defence. Just like Mr Palmer in the case above – you know exactly what you are doing, you’re just mistaken about being able to legally do it at that location.

If, however your speedometer was faulty you may have a defence. If you’re aware of the limit and, based on a faulty speedo, you honestly and reasonably believe you are obeying the speed limit then it is a mistake of fact. Even in these matters, the reasonableness of your belief would be considered. For example, if you were travelling twice as fast as all the other vehicles around you, it is less likely to be reasonable. Or if you have modified the vehicle but not recalibrated the speedometer you may not be successful. You would also need to obtain a report from a mechanic or other qualified person that the speedometer is not accurate.   

Driving while suspended

There are two main types of licence suspensions. The first is an immediate suspension issued by police. The other are suspensions issued by post from either the RMS / TfNSW or SDRO. These are for things like speeding, exceeding your demerit point limit, or non-payment of fines.

If you do not receive a letter advising you that your licence is suspended, then you may be able to raise an honest and reasonable mistake offence. Even in these cases there are some factors that result in you being unsuccessful. If you have changed address and not notified authorities, then it is unlikely to be reasonable. Similarly, if you pay a number of fines knowing that it will result in a suspension, yet make no further enquires about your licence status, a court may not find your mistake to be a reasonable one.

Driving while disqualified

Disqualifications are only imposed by a court. If you don’t attend court for some traffic offences, you may be convicted in your absence and disqualified. The court will post the outcome and orders to your residential address. As with the example above, if you’ve changed address but not notified anyone, it may not be a reasonable excuse. Similarly, it may not be seen to be reasonable if you knew that you had to attend court and made no further enquiries after failing to attend.

You also need to believe in a state of affairs which if true, would render you innocent of any offence. If a disqualified driver tells the police or court that they believed they were only unlicensed or suspended – they cannot rely on this defence. That is because they don’t hold a factual belief which, if true, would mean they are innocent of any offence. They know they cannot drive – they are just mistaken as to why.

Drink driving

In very rare occasions, honest and reasonable mistake of fact is raised in drink driving or drug driving matters. It requires the person charged to satisfy the court that they honestly and reasonably believed that they were under the limit. Obviously the closer to the legal limit a person is, the more likely that belief would be reasonable.

If you’ve been charged

If you’ve been charged with any criminal or traffic offence it’s important to speak to an experienced criminal & traffic lawyer as soon as possible.