The best defence always depends on the circumstances of the crime and the evidence against you. Here are some common defences that can be used.
Justification
Where you admit what you did could be viewed as a criminal act but that it was justified by external circumstances, such as self defence.
Provocation
Section 232 (1) of the Criminal Code states that a culpable homicide that would ordinarily be considered a murder may be reduced to manslaughter "if the person who committed it did so in the heat of passion caused by sudden provocation." With charges like assault, provocation does not act as a complete defence but it can mitigate damages or culpability.
Necessity
This defence is rooted in common law and has been recognized in Canadian courts since 1984. This defence can be raised for actions committed when there is a clear danger and the accused has no safe avenue of escape or legal way out of the situation.
Duress
Section 17 of the Code states that if you commit an offence because you are being threatened with death or body harm by another person you can be excused for committing the offence. This defence does not apply if the offence is treason, murder, piracy, attempted murder, sexual assault, sexual assault with a weapon, threatening to cause bodily harm, aggravated sexual assault, forcible abduction, hostage-taking, robbery, assault with a weapon, aggravated assault, unlawfully causing bodily harm, arson or any offence involving the abduction and detention of a young person
Self-defence
Section 34 of the Code states you cannot be convicted of an offence if you believe "on reasonable grounds" that force is about to be used against you or another person and you have to take action to defend yourself or others.
Mistake of fact
The defence refers to a misunderstanding of the situation that led you to unknowingly commit a crime. For example, if you are charged with theft, you could argue you honestly thought the property in question belonged to you.