The common law defence of necessity operates where circumstances (natural or human threats) bear upon the accused, inducing the accused to break the law to avoid even more dire consequences. There is, thus, some overlapping with the defence of duress.
In order to raise necessity, the following elements have to be established by way of evidence:
- The criminal act must have been done in order to avoid certain consequences which would have inflicted irreparable evil upon the accused or upon others whom he or she was bound to protect;
- The accused must honestly have believed on reasonable grounds that he or she was placed in a situation of imminent peril; and
- The acts done to avoid the imminent peril must not be out of proportion to the peril to be avoided.
The accused bears the evidentiary onus of establishing a basis for a defence of necessity and, thereafter, the Crown bears the onus of negativing the defence beyond reasonable doubt.