How far can you forgive an honest mistake? Mr de Menezes was running late for work one summer morning in July. As he took his seat on the train police officers shot him 7 times in the head and once in the shoulder from close range. Three more shots missed their target. The police had followed the wrong man, mistaking an ordinary commuter for a terrorist. They killed an innocent man, but the police officers were not guilty of murder, nor of manslaughter. They were never charged with a criminal offence. It was all a terrible, but honest, mistake.

A situation like that is horribly confused, but the law that applies to it is simple. As a general rule, the criminal law will judge people’s reactions in the context of what they knew or believed was going on around them. The shooters believed they had to fire or a terrorist would blow up a crowded underground train.

In Queensland, our ideas about such honest mistakes are set out in section 24 of the Criminal Code. Our rule is a bit different to that chosen by some other States and countries. Queensland adds two interesting layers to the defence. Firstly, the honest mistake must also be a reasonable mistake. That’s a simple enough concept to understand. Secondly (and you might think that this too is a fairly simple idea) a person is not responsible for their actions “to any greater extent” than they would have been if the situation really was as they believed it to be. Is that a difficult concept?

For over a hundred years, Queensland’s judges had no difficulty with the idea that a person might be guilty, but to a greater or lesser extent, depending on their mistake. Take the case of a plain-clothes police officer who is punched in a brawl. The puncher probably believed his victim was not a police officer. In 1941, Justice Philp said such a puncher could be found guilty of assault, but he could not be found guilty of the more serious charge: assaulting a police officer. Justice Philp noted that the result would be different in English law. The 1875 English case of R v Prince[1]would not be followed in Queensland.[2] In 1987, two judges of the High Court of Australia quoted Justice Philp’s approach to interpreting the Code with approval.[3]

A year earlier, in 1986, a Mr Lyons was searching for sexual partners in the public toilets of a Graceville park. The adventure ended unhappily and he found himself arrested and charged with sexual assault. Part of Mr Lyons’ defence was that he believed the other man consented. This was in the days when all homosexual activity was illegal, so Mr Lyons admitted in effect to the offence of gross indecency, but his point was that it was not an assault. The Court of Appeal agreed unanimously that an honest and reasonable belief in consent would be a good defence to the assault charge. That was so despite Mr Lyons knowing that what he was doing was still illegal, even if the other man consented.[4]

Years passed. In 2007, a man known to the public only as “SBC” had been convicted of groping a young girl as she lay next to him on the couch. The charge was indecent dealing with a child under 16. He told the police, “I was drunk and that’s the reason that – that I did it, ah, and I thought I was with (the girl’s mother).” The Court of Appeal held, unanimously, that would be a good defence to the charge, even if the same thing done to the mother might be an indecent assault. A re-trial was ordered.[5]

Then in 2009 came perhaps the clearest example. The girl was 13 years old and Bradley John Phillips knew it. The only issue was whether he had an honest and reasonable belief in her consent, and on 2 of the charges the jury gave him the benefit of doubt. Then the Court of Appeal gave him the same benefit on a third charge. Instead of rape, he was convicted of unlawful carnal knowledge.[6] For our purposes, the point of law from the case is that, even though Phillips knew perfectly well he was breaking the law with an underage girl, his mistake meant that he was guilty of the lesser charge. To use the words of section 24, he was criminally responsible, but not “to any greater extent” than he would have been in the world as he believed it to be.

The law applied in Phillips’ case was uncontroversial. The lawyers involved agreed with it. There were no mutterings in chambers, no articles of scholarly disquiet. It was the straightforward application of well established, well understood principles. Further research might be expected turn up other cases with similar facts where the Court of Appeal has taken the same approach.

So, with about 115 years of experience to go by, lawyers in Queensland were fairly comfortable with their understanding of how section 24 worked, but you know you should never get too comfortable. Along came Mr Duong’s case. In 2013 a search of Mr Duong’s car turned up more than 200 grams of powder. The powder contained a drug called methylamphetamine, sometimes nicknamed meth, or ice, or speed. Mr Duong was charged with possession of a drug in the most serious category (Schedule 1). Part of Mr Duong’s evidence at his trial was that he believed the powder was another drug called DMA. This evidence was not entirely helpful to his defence, because DMA was an illegal drug. It was however, in the less serious category (Schedule 2)[7], and so possession of DMA would be a lesser offence.[8]

The trial judge, Justice Dalton, told the jury that Mr Duong’s belief on that score was irrelevant. He would not have a mistake of fact defence unless he believed the substance was not any type of illegal drug.[9] Mr Duong was convicted and filed an appeal.

Justice James Douglas delivered the judgement of the Court of Appeal.[10] He decided that a mistake is only a defence to a charge of drug possession if the accused person believes they possess something which is not an illegal drug.[11] A first reading might give the impression that in Justice Douglas’s view the effect of section 24 of the Queensland Code is no different than the common law of England expressed in the case of R v Prince in 1875; the very same case Justice Philp said way back in 1941 should not be followed here. A closer reading suggests that the common law was considered as “background”[12] and the decisive point may have been that Mr Duong’s claimed belief still left him guilty of an offence “within the confines of the counts charged on the indictment”.[13]

Unfortunately, none of the decisions of the Court of Appeal from 1941 to 2009 cited above are referred to in the judgement, and the Court may not have been taken to them in argument.[14]

Now Queensland has some peculiar drug laws,[15] and they could have complicated Mr Duong’s appeal. However, those complications can be disregarded in this discussion because the judgement of the Court of Appeal did not rely on them.[16] It turned on the construction of section 24.

Mr Duong’s case is now cited in the criminal lawyer’s first resource, Carter’s Criminal Law of Queensland [17]. Although the issue is described there merely as a mistake about the type of dangerous drug, there is every chance that prosecutors will seize upon it to limit the scope of a mistake defence in other types of cases, as well as drug cases.

Consider the example of a truck driver, who overloads his truck with cartons of untaxed tobacco. He knows he’s breaking the law. He knows the cargo is prohibited. Some of the cartons turn out to contain heroin. He didn’t know about the heroin. Is his honest and reasonable mistake a defence to possessing a dangerous drug?

From a policy view, the previous approach of Queensland’s courts leads to more just outcomes. The criminal can be convicted of an offence proportionate to the wrong that it would have been in the situation they  they honestly and reasonably believed existed. The truck driver can be convicted in relation to the tobacco, but not the heroin.

On a strictly legal approach, the words “to any greater extent” in the Code must be assumed to have some meaning. On Justice Douglas’ interpretation those words have no work to do at all, and the section would have the same meaning if the words were removed. The Court in Duong did not consider the earlier authorities such as Phillips, and the reasoning at the core of the judgement cannot be reconciled with the earlier cases Phillips, SBC, or Lyons.[18]

The innocuous annotation in Carter’s suggests that this might become one of those cases which over time is quietly “confined to its facts”, perhaps even overlooked. It has not been selected for inclusion in the Queensland Reports. However, if prosecutors rely upon the broader statements of common law principle, then the issue is bound to come squarely before the Court of Appeal, which will have to grapple with its own conflicting authorities. It’s so easy for anyone, even a judge, to make an honest mistake.


Ken Mackenzie is an accredited specialist in criminal law.

Mackenzie Mitchell Solicitors acted for Mr Duong in an unsuccessful application to the High Court for special leave to appeal.

[1] R v Prince [1875] LR 2 CCR 154 per Bramwell B at 176; [1874-80] All ER 881

[2] Anderson v Nystrom [1941] St R Qd 56 at 70 per Philp J, with whom E.A.Douglas J agreed at 62. The observation on this point was of no relevance to the determination of the case. In Commissioner of Police v Stebhens [2013] QCA 81 the Court of Appeal assumed that a mistaken belief that the complainant was not a police officer would provide a defence, per M.Wilson J at [15] with whom Gotterson JA and Douglas J agreed. The present Benchbook says nothing about whether a mistaken belief that the person was not a police officer provides a defence, although there is reference to actual knowledge of that fact not being relevant to the offence, supported by a citation to R v Reynhoudt [1962] HCA 23; (1962) 107 CLR 381 at 395 and 397, which was an appeal from Victoria concerning the mens rea for the offence in a common law jurisdiction.

[3] Walden v Hensler (1987) 163 CLR 561, per Brennan J at 567 and Deane J at 580. Although their comments were specifically with reference to section 22 of the Code, the same point about reference to the common law applies to section 24.

[4] R v Lyons (1987) 24 A Crim R 298, per Williams J at 300 and Moynihan J (with whom Andrews CJ agreed) at 302. Although Mr Lyons won the law he lost the facts. He failed to persuade the court that there was evidence of a reasonable belief. His appeal against conviction was dismissed.

[5] R v SBC [2007] QCA 283

[6] R v Phillips [2009] QCA 57; [2009] 2 Qd R 263

[7] Listed in Schedule 2 at the time as “2,5-Dimethoxyamphetamine (2,5-DMA)”

[8] Strictly, the same basic offence but with a less serious circumstance of aggravation; that is, possession of a drug in Schedule 2 (maximum 15 years imprisonment, and can be heard summarily) under s.9(d), rather than possession of a drug in Schedule 1 over the Schedule 4 quantity (maximum 25 years imprisonment) under s.9(a) Drugs Misuse Act 1986. At the time of the offence in 2013 the drug DMA was not listed in Schedule 3 so there was no quantity which would enliven s.9(c).

[9] [5] of the appeal judgement.

[10] R v Duong [2015] QCA 170, Fraser JA and Flanagan J agreed with Douglas J without further comment.

[11] At [55] [12] At [53] to [54] [13] At [55]. The judgement makes little reference to the procedural effect of charging circumstances of aggravation, and why a mistaken belief should or should not be relevant to the circumstance of aggravation. The reference in this paragraph of the judgement to a special verdict taken under s.624 is, it is submitted, mistaken. Correctly, a verdict in relation to circumstances of aggravation should be taken under s.575. That is, the circumstance of aggravation is always solely a decision for the jury in Queensland (see also s.564(2)), not simply a fact that may be relevant to the appropriate sentence, and not a fact to be determined by the sentencing judge. If that proposition is correct, then doubt is thrown on a line of authority from R v Jacobs [1997] QCA 114; [1998] 1 Qd R 96. The concession by the Crown in R v Geary [2002] QCA 33; [2003] 1 Qd R 64 at [5] was correct and the comments in that case at [12] are obiter and the analogy used is inapt (there is no circumstance of aggravation to manslaughter).

[14] Had it been, Douglas J might have considered that he was disagreeing not only with himself (footnote 2), but also with his great-uncle E.A.Douglas J (also footnote 2). One interesting point about that is that the present Douglas J opined at [50] that the author of the Criminal Code, Sir Samuel Griffith, must have been aware of the English cases including Prince, and intended s.24 to replicate the common law. Great-uncle E.A. Douglas J had served as an associate to Sir Samuel Griffith but reached the opposite conclusion.

[15] Section 129 Drugs Misuse Act 1986

[16] See [38], [46] and [56] [17] 21st edition at [24.55] [18] Strictly perhaps, Lyons is not binding as his appeal was dismissed. In both Phillips and SBC the orders made were based on the premise that a mistaken belief could lead to conviction of a different, lesser offence.

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  1. Eugene OSULLIVAN says:

    Thanks Mate. Should have been a HCA appeal. Keane and Keiffel would fix it

    • Ken Mackenzie says:

      In other States the sentencing judge can decide whether the accused committed the circumstance of aggravation. It was perhaps unfortunate for Mr Duong that Justices Gageler and Nettle heard the application for special leave, and not the judges with a Queensland background.

  2. Ken Mackenzie says:

    In R v Schafer [2017] QCA 208 the Court of Appeal proceeded on the assumption that a reasonable mistaken belief as to consent would provide a defence to a charge of rape, notwithstanding that the complainant was less than 16 years of age and consensual sexual intercourse with her would be a crime.

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