Defences
When the Crown is able to prove the elements of the offence beyond a reasonable doubt, the defence may still avoid conviction by raising a positive defence.
A true defence arises when some circumstances afford the accused a partial or complete justification or excuse for committing the criminal act. In Canada, the defences are generally similar to standard and popularly understood defences of other common law jurisdictions such as the U.K., Australia and the United States. The true defences include duress, automatism, intoxication, or necessity. There is also a partial defence of provocation, which has the effect of reducing what would otherwise be murder to manslaughter. This partial defence is provided by s.232 of the Criminal Code.
Some defences are provided for by statute and some defences are provided for solely by the common law. In some cases common law defences are superseded by statutory enactment, for example duress, self-defence and as mentioned above, extreme intoxication. Interestingly, in the case of duress the Supreme Court of Canada struck down the statutory provision as violative of s.7 of the Charter, leaving the broader common law defence instead. Statutory encroachments on the scope of common law defences can violate s.7 of the Charter if they unacceptably reduce the fault requirement of offences.
In addition to the true defences as mentioned above, there are other "defences" in a broader sense. In some cases, these "defences" are really just an assertion that the Crown has not proven one of the elements of the offence. For example, the mistake of fact defence involves an assertion that the accused misunderstood some material factual matter that prevented him from forming the requisite mens rea for the offence. In the context of sexual assault, for example, a mistake of fact defence usually involves an assertion that the accused did not realize the complainant was not consenting. Since the mens rea for sexual assault includes a subjective appreciation of the fact that the complainant is not consenting, the "defence" of mistake of fact in this context is thus properly understood as a failure on the part of the Crown to prove its case. In practical terms and common parlance, however, it is still considered to be a defence. Another example of this more general kind of defence is the "i.d. defence", which is really just an assertion by the accused that the Crown has failed to prove the identity of the perpetrator of a crime beyond a reasonable doubt. There are many other examples of this kind of defence. In reality they are just clusters of specific shortcomings that arise frequently in the prosecution of certain kinds of offences.
All defences – whether one is speaking of true defences or defences in the broader sense – can arise from the evidence called by the Crown or the accused. A defence can only be left with the jury (or considered by a judge trying the case without a jury) where there is an "air of reality" to the defence on the evidence. That air of reality can arise from the Crown's case and/or from the defence case if one is called. It is not necessary for an accused to testify or call other evidence to raise a defence. If the evidence called by the Crown is sufficient to raise an air of reality to a defence, the jury must consider whether the defence applies, most on the standard of whether it raises a reasonable doubt. For example, in an assault case it may be that one of the Crown's eyewitnesses testifies that it looked to him like the victim punched the accused first and that the accused was defending himself. In such a case, even if all the other eyewitnesses saw the accused punch first, the jury must consider whether on all of the evidence it has a reasonable doubt that the accused acted in self-defence.
There is an even broader sense of the word "defence". Sometimes the defence will raise an issue capable of leading either to the termination of the proceedings or the exclusion of evidence. For example, in a drug case the accused might argue that the search warrant by which the police entered his house and seized the drugs was defective and that his constitutional rights were therefore violated. If he is successful in establishing such a violation, the evidence can be excluded, and usually the Crown cannot otherwise prove its case. When this sort of thing happens, it is not really a defence at all, since the accused must establish it in a separate pre-trial application. Nevertheless, lawyers often refer to such applications as a "Charter defence" in reference to the Charter of Rights.
Other forms of Charter defence can lead not to the exclusion of evidence but to the termination of the proceedings, known as a stay of proceedings. For example, if the accused is not brought to trial within a reasonable time, the proceedings must be stayed for delay by virtue of ss.11(b) and 24(1) of the Charter. Stays of proceedings can also take place in the absence of a Charter violation. For example, the familiar "defence" of entrapment is neither a true defence nor necessarily a Charter breach. When entrapment is successfully established, the proceedings are deemed to be an "abuse of process" for which the remedy is a stay of proceedings. Cases of abuse of process arise in certain other circumstances, and they can also can involve Charter breaches, and there is significant overlap.
Finally, ignorance of the law is not a defence. Section 19 of the Criminal Code specifically prohibits this defence. However, in rare cases ignorance of a law other than the one under which the accused is charged can be a defence if knowledge of that law is a relevant circumstance required to be proved as part of the actus reus and/or mens rea.
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