Intoxication
Intoxication is when a person’s mental state is impaired as a result of taking alcohol or drugs.
In general, intoxication is not a valid excuse as a defence for crimes. The law holds people responsible for putting themselves in a state of intoxication and for the consequences of their actions while in this state.
However, intoxication can be used as a defence for crimes of specific intent. These are crimes in which there is an added criminal purpose in addition to the criminal act itself. Ex. Murder, break and enter with intent to commit an indictable offence. Specific intent offences have a higher standard of mens rea, requiring the court to prove specifically what was in the mind of the accused at the time of the crime.
If a person was in a state of intoxication in which they could not form the specific intent to commit the offence, then a court can’t prove conclusively that they have the guilty mind.
In these cases, intoxication can be used to drop the charges down to a lower, general intent offence. Ex. murder to manslaughter.
Automatism
Non-insane Automatism: when a person is in a state of unconscious, involuntary action, in which they are capable of action but not conscious or in control of what they are doing. Relates to the actus reus of the offence.
Non-insane automatism is not a defence in the criminal code, but has emerged from case law as a recognized defence. Stroke, seizure, a blow to the head, sleepwalking, and severe psychological trauma are some of the 
conditions that can put someone in a state of automatism.
Like all defences, it is up to the accused to prove the defence is valid in the case. To prove automatism, the accused must put forward substantial evidence, based on expert testimony (doctor, psychiatrist)
If automatism is used, it leads to a complete acquittal (finding of not-guilty). Several cases in Canadian law have recognized and helped define automatism, some of which have been controversial. In R. v. Parks, a person charged with murder was found not guilty b/c they successfully argued that they were in a state of automatism due to sleepwalking.
Mental Disorder (Insane Automatism)
Defintion: A state of mind in which a person is not able to understand the nature and consequences of their actions, as a result of mental disorder. Mental disorder relates to the mens rea of the crime
In the criminal code, it states that if a person is suffering from a mental disorder at the time of the crime, and thus is not able to appreciate the nature of the act, they are not criminally responsible for the offence.
Mental disorder can be raised be either the crown, or the defence; which ever party raises it has to prove it.
Before a case can move forward with a finding of NCR, a separate hearing is held to determine if the accused is fit to stand trial. The hearing must answer the following:
Does the accused understand the nature of the court proceedings and the possible consequences?
Can the accused communicate with their lawyer?
If the answer is no, then a trial is postponed until a later date and the accused is held in a psychiatric facility. If a trial proceeds and there is a finding of NCR, then the accused is assigned to treatment in a psychiatric facility, instead of a prison.
