2. The question on which the Crown seeks the decision of this Court is one on which there has recently been a division of opinion in the Supreme Court. It is one of undoubted importance if only because of the desirability that there should be certainty in the criminal law, particularly where the offence is an indictable one in which the judge presiding at a trial is required to explain to a jury in terms understandable by laymen what are the essential elements in the crime which must be proved by the Crown. The question for decision is the extent to which the element of mens rea is necessary to create an offence under the section. The learned Solicitor-General, who appeared in support of the application, told us that in Victoria the provision in question and its predecessors in similar language have until recently been interpreted by the courts as requiring the Crown to prove an assault or an act of resistance or of wilful obstruction; that the person assaulted, resisted or obstructed was a police officer; and that he was acting in the due execution of his duty, but that mens rea in relation to these last two essential facts is not required to be shown. And this appears to be the construction which has long been placed upon the counterpart of the section in England. In April 1961, in the case of Reg. v. Galvin (No. 1) [1961] VicRp 113; (1961) VR 733 , the question was debated and considered by the Court of Criminal Appeal (Gavan Duffy, Sholl and Adam JJ.). Their Honours were of opinion that knowledge on the part of the accused that the person assaulted was a police officer or that he was acting in the due execution of his duty was "not part of the definition of the offence and need not be proved by the prosecution in the first instance as part of its essential case" (1961) VR, at p 738 . It was sufficient, their Honours said, for the Crown to prove an assault, that the person assaulted was in fact a police officer and that he was in fact acting in the due execution of his duty. If these facts were proved by the Crown the accused, their Honours went on to say, might nevertheless exculpate himself by showing, on a balance of probabilities, that he had "acted reasonably in the bona fide belief, based on reasonable grounds, that the police officer was in fact unlawfully assaulting or otherwise interfering with him, or, it may be, unlawfully assaulting or otherwise interfering with another person, and that, had the facts been as the accused supposed them to be, his own actions would have been lawful and innocent" (1961) VR, at p 738 . For various reasons, into which it is unnecessary to go, the Court of Criminal Appeal was of opinion that Galvin was entitled to a new trial and made an order accordingly. On the second trial the learned trial judge gave directions to the jury on this point in accordance with what the Court of Criminal Appeal had said. Galvin was convicted and again appealed to the Court of Criminal Appeal. On this occasion, Reg. v. Galvin (No. 2) [1961] VicRp 114; (1961) VR 740 , the Court consisted of five judges (O'Bryan, Barry, Dean, Sholl and Hudson JJ.) and the decision in Reg. v. Galvin (No. 1) [1961] VicRp 113; (1961) VR 733 was reviewed. The majority of the Court (O'Bryan, Dean and Hudson JJ.), after pointing out that the assault, resistance or wilful obstruction necessary to be proved as an element in the offence must be an intentional act, as clearly it must be, said: "Surely the common law requirement that the assault must be intentional is to be carried forward into these aggravating elements of the new offence. The accused must intend to assault and he must intend to assault a policeman in the due execution of his duty. In most cases this intent would be proved by evidence that he knew it was a policeman and supposed that he was acting in the due execution of his duty. But knowledge in the strict sense may not be necessary in all cases. For example, if an evilly disposed person were to say - 'This fellow looks like a policeman on duty, I hate all policemen, I will assault him'. If he acted on this intention he would in our opinion have the necessary mens rea to be guilty of this offence, not because he actually knew his victim to be a policeman, but because he intended to assault a policeman in the due execution of his duty, and if the necessary actus reus were proved, viz. that the assaulted person was in fact a member of the police force in the due execution of his duty, full guilt could be proved" (1961) VR, at pp 748, 749 . Barry J. was of opinion that knowledge by the accused that the person assaulted was a police officer and was acting in the due execution of his duty were essential parts of the Crown case but was unable to agree with that part of the judgment of the majority judgment which laid down that "knowledge in the strict sense may not be necessary in all cases" (1961) VR, at p 748 and which gave as an illustration the case of the evilly disposed person who committed an assault upon another not knowing that he was a policeman but hoping that he was. Sholl J., who dissented, considered that the law as laid down in Reg. v. Galvin (No. 1) [1961] VicRp 113; (1961) VR 733 was correct. After the decision in the second Galvin Case [1961] VicRp 114; (1961) VR 740 had been given, the respondent to the present application was put upon his trial and, in the course of it, the learned trial judge, whose attention was not drawn to the second Galvin decision [1961] VicRp 114; (1961) VR 740 , charged the jury in accordance with what had been said in the first Galvin Case [1961] VicRp 113; (1961) VR 733 . A conviction followed. The respondent appealed to the Court of Criminal Appeal (Herring C.J., Sholl and Little JJ.) which upheld the appeal, stating merely that the jury had been charged in a way "inconsistent with the view expressed in the second Galvin Case [1961] VicRp 114; (1961) VR 740 . That being so, we are bound to accept that decision and give effect to it". Accordingly their Honours allowed the appeal, quashed the conviction, and ordered a new trial. (at p405)