73. In many cases, the cause of the unfitness to plead may well have also enabled the accused to benefit from a verdict of not guilty by reason of mental impairment. In others, the same condition, though falling short of that defence, may have negatived a specific intent as where particular consequences are to be foreseen (for example, s 30 of the Crimes Act - Threat to kill) albeit that a lesser offence might be made out. In yet other instances, the cause of the unfitness to plead may have arisen after the alleged offence.
74. It would plainly be unsatisfactory so far as the accused is concerned, if, on the facts as proved to the requisite degree, it appears that the accused should have been acquitted of the offence charged because there was reason to doubt that a specific intent, an element of that offence, existed. It may even be the case that it is apparent, by reason of, for example, mental retardation, that the accused could not have had that specific intent. It would be plainly absurd to find that the accused had committed the acts constituting that offence when it appears that the accused did not have a specific intent or specific knowledge necessary to constitute one offence rather than another, perhaps, lesser offence - for example, assault occasioning actual bodily harm, as opposed to assault with intent to cause grievous bodily harm.
75. On the other hand, in a case such as was considered in Antoine (supra), the accused had voluntarily and intentionally killed a person. His mental state at the time may have entitled him to rely on diminished responsibility or even insanity. Had either of those pleas succeeded, a committal to hospital on a mental health order was a likely result. Indeed, as noted, a co-accused was so committed on acceptance of a plea to manslaughter by reason of diminished responsibility. It would be anomalous that an accused could be entirely acquitted if unfit to plead by reason of the same or a similar mental impairment but if tried might, at best, be found not guilty on the ground of insanity and then detained under a similar order.
76. It seems to us that it is consistent with the purpose of the legislation for the Crown to be relieved of the obligation to prove that the accused had the requisite mens rea for the offence where there is evidence of mental impairment warranting a finding of diminished responsibility or of insanity which, otherwise, would be a defence.
77. Nevertheless, if the offence charged requires a specific intent of the particularity necessary to constitute the offence, such as the offence of arson referred to in s 117 Crimes Act, "to endanger the life of another person", that specific intent must be proved in order that the "acts" proved will constitute that offence rather than a lesser offence.
78. If the specific intent or knowledge is present, it is no answer for it to appear that that specific intent or knowledge was the consequence of mental impairment. However, the mental impairment will be relevant to the question whether that intent or knowledge was in fact present.
79. That, it seems to us, is the consequence of Lord Hutton's speech in Antoine (supra). His Lordship points to the fact that a person unfit to plead, as with any other person who offers no answer to the prosecution case, will be at greater risk of adverse findings if the evidence adduced satisfies the jury that the acts constituting the offence were done apparently voluntarily and intentionally. In such a case, unless some matter of excuse appeared, at least as a reasonable hypothesis (for example, self-defence or accident), the offence would be made out.
80. This is no different from the situation where a person who is fit to plead faces a charge, say, of assault. The prosecution does not have to negative self-defence unless from the evidence it appears that it is reasonably possible that the act in question was done in self-defence (see Zecevic v DPP (Vic) [1987] HCA 26; (1987) 162 CLR 645, 657). Some objective evidence must appear which fairly raises that hypothesis.
81. It is not incumbent on the Crown to prove that the accused was of sound mind at the time the alleged offence was committed. However, even in cases where insanity is relied upon as a defence, the Crown is not relieved of the burden of proving that the acts allegedly done were done voluntarily and intentionally and that any specific intent or knowledge necessary to constitute the particular offence alleged was present. To hold otherwise would lead to the ludicrous situation that possession of stolen goods would lead to liability for incarceration, at least on a mental health order, if the alleged offender was unfit to plead, but not if it appeared at trial that he lacked knowledge that the goods had been stolen. It would be no answer to say that, had the accused not been mentally impaired, he would have realised that the goods were stolen.
82. It is different where the facts as proved would warrant a finding adverse to the accused but for the application of the mental impairment defence. In that case, the mentally impaired defendant is not guilty on the ground of mental impairment and would be treated in the same way as that same defendant would be treated at a special hearing following a non-acquittal. Indeed, given that a person unfit to plead cannot elect an ordinary criminal trial, a different result would be anomalous.
83. The Crown is assisted by the presumption that an accused person is of sound mind, at least to the extent of being, until the contrary is proved, of normal understanding and awareness.
84. There is no legal presumption as to acts done being voluntary and intentional - see Parker v The Queen [1963] HCA 14; (1963) 111 CLR 610. However, in the absence of evidence to the contrary a jury (or judge alone) is entitled to infer that the act in question was voluntary and intentional. Further, to find that an apparently voluntary and intentional act is a product of mental impairment depends on proof of that fact at least to the civil standard.
85. It is consistent with Antoine that where the evidence otherwise reveals a voluntary and intentional act and, if required by the offence charged, actual knowledge or specific intent in relation to a particular matter, then it is open for a tribunal of fact so to conclude unless there is raised by the evidence some reason to doubt that conclusion apart from the potential application of the defence of mental impairment (or, if applicable, diminished responsibility).
86. In other words, lack of intent, specific or general, arising from mental impairment or, where relevant, diminished responsibility, falls outside the scope of "acts constituting the offence".
87. Similarly, "diminished responsibility" as a defence (s 14 Crimes Act) does not need to be negatived by the Crown. It is applicable only on a trial for murder where the accused is in jeopardy of being convicted of murder. The evidence that might support a conclusion of diminished responsibility could in some circumstances support a finding that, doubt being raised as to the voluntariness of the act in question, or as to a specific state of knowledge or intention, the Crown has failed to dispel that doubt. However the two questions are not identical.
88. Similarly the defence of provocation (s 13 Crimes Act) will be unavailable on a special hearing. It applies only to a trial for murder where the accused person could otherwise be convicted of murder.