The defence of duress exists both in statute under s. 17 of the criminal Code and under the common law.
The common law defence pre-dates the provisions of s. 17, however, by function of s.8 of the Criminal Code, which preserves all common law defences, the broader common law defence is still considered.
The distinction between the two is that the s.17 defence does not apply to parties, including aiders and abettors. The common law, however, can still apply for parties to the offence.
Duress is an excuse-based defence.
- Section 8 (3) state:
Common law principles continued
(3) Every rule and principle of the common law that renders any circumstance a justification or excuse for an act or a defence to a charge continues in force and applies in respect of proceedings for an offence under this Act or any other Act of Parliament except in so far as they are altered by or are inconsistent with this Act or any other Act of Parliament.
R.S., 1985, c. C-46, s. 8; 1993, c. 28, s. 78; 2002, c. 7, s. 138.
- R. v. Wilson, 2011 ONSC 3385 at 50
Compulsion by threats
17. A person who commits an offence under compulsion by threats of immediate death or bodily harm from a person who is present when the offence is committed is excused for committing the offence if the person believes that the threats will be carried out and if the person is not a party to a conspiracy or association whereby the person is subject to compulsion, but this section does not apply where the offence that is committed is high treason or treason, murder, piracy, attempted murder, sexual assault, sexual assault with a weapon, threats to a third party or causing bodily harm, aggravated sexual assault, forcible abduction, hostage taking, robbery, assault with a weapon or causing bodily harm, aggravated assault, unlawfully causing bodily harm, arson or an offence under sections 280 to 283 (abduction and detention of young persons).
R.S., 1985, c. C-46, s. 17; R.S., 1985, c. 27 (1st Supp.), s. 40.
The requirements of s.17 to have “presence” and “immediacy” is unconstitutional for violating s.7. Thus, that portion of the section has no force or effect.
Despite the existence of the common law defence, all offences listed as defence exceptions in s.17 cannot be covered by common law. Any included offences to offences to the exempted offences listed in s. 17 are also exempted from the statutory defence.
- R v Ruzic 2001 SCC 24
- R. v. Mohamed, 2012 ONSC 1715 at 20
- R v Li 2002 CanLII 18077 (ONCA) -- kidnapping charge was also exempted as part of the abduction charge
At common law, duress is an available defence to any offences short of murder. It must be shown that the accused's will was overborne by threats of death or serious personal injury such that accused is not acting voluntarily.
There are three elements to the defence. It must be established that:
- the accused must be subject to a “threat of death or serious physical injury”
- on an objective standard, no safe avenue of escape existed  or any “reasonable opportunity to render the threat ineffective.”
- “there must be proportionality between the threat and the criminal act alleged”
If the defence is raised, the Crown has the burden of proving beyond a reasonable doubt that at least one of the elements is not available.
The threat need not be of immediate death or bodily harm. 
The defence will not be available through the common law where the accused puts themselves in a position where they are likely to receive threats.
"the defence in Canada, ...[is] an objective-subjective standard, as in the case of the defence of necessity" (Ruzic at para 71).