The offence of administer noxious substance is contained in section 245(1) of the Criminal Code.
A person commits the offence of administer noxious substance when they administer, cause to be administered to any other person, or cause any other person to take poison, or any other noxious or destructive substance.
Person A and person B work together in a shopping mall. They do not get along. Angry with person B, person A pours toxic cleaning solution into person B’s water bottle.
Person C switches the label on a bottle of bleach to make it appear as though the bottle contains fruit juice, knowing person D often drinks the juice. Person D drinks the bottle of bleach, believing it to be fruit juice.
R. v. Tsoraklidis,  ONCJ 279
In R. v. Tsoraklidis, the offender was charged with administer noxious substance after pepper spraying a gas station attendant without provocation. The offender argued at trial that he was acting in self-defence, though this evidence was rejected by the court. The offender was convicted.
Offence Specific Defence(s)
Pursuant to section 245(2), a medical practitioner or nurse practitioner who provides medical assistance in dying in accordance with section 241.2 of the Code, and any person who provides assistance to the doctor or nurse, will not be guilty of administer noxious substance.