R. v. Daley, 2007 SCC 63, is the leading case on intoxication in Canada. It outlines the three categories of intoxication and the application of those categories:
 Our case law suggests there are three legally relevant degrees of intoxication. First, there is what we might call “mild” intoxication. This is where there is alcohol-induced relaxation of both inhibitions and socially acceptable behaviour. This has never been accepted as a factor or excuse in determining whether the accused possessed the requisite mens rea. See Daviault, at p. 99. Second, there is what we might call “advanced” intoxication. This occurs where there is intoxication to the point where the accused lacks specific intent, to the extent of an impairment of the accused’s foresight of the consequences of his or her act sufficient to raise a reasonable doubt about the requisite mens rea. The Court in Robinson noted that this will most often be the degree of intoxication the jury will grapple with in murder trials
In most murder cases, the focus for the trier of fact will be on the foreseeability prong of s. 229(a)(ii) of the Criminal Code, R.S.C., 1985, c. C‑46, that is, on determining whether the accused foresaw that his or her actions were likely to cause the death of the victim. For example, consider the case where an accused and another individual engage in a fight outside a bar. During the fight, the accused pins the other individual to the ground and delivers a kick to the head, which kills that person. In that type of a case, the jury will likely struggle, assuming they reject any self‑defence or provocation claim, with the question of whether that accused foresaw that his or her actions would likely cause the death of the other individual. [para. 49]
A defence based on this level of intoxication applies only to specific intent offences.
Mild intoxication is not a defence to any crime.
Advanced intoxication acts on specific intent offences. In the case of Murder, advanced intoxication will reduce it to Manslaughter.
Finally, there is Extreme intoxication. Extreme intoxication renders a person not-criminally-responsible:
 The third and final degree of legally relevant intoxication is extreme intoxication akin to automatism, which negates voluntariness and thus is a complete defence to criminal responsibility. As discussed above, such a defence would be extremely rare, and by operation of s. 33.1 of the Criminal Code, limited to non-violent types of offences.
Daley also discusses when the trial judge must instruct the jury on intoxication, and the content and form of a proper jury instruction on this issue (See paras 44-53).