2. Causality: "chains of causation," "thin skulls" and "novus actus interveniens"

A crucial element of some criminal offences, notably homicides, is proof that the actus reus actually caused a certain consequence. Causality may seem commonsensical but what we might describe as causal in ordinary parlance is not necessarily what counts as causal in law. Note that in this session we are only concerned with actus reus causality, not any potential corresponding mens rea requirement. In other words, the question is whether the act actually caused the consequence not whether that was intentional, for example.

Causality is a fairly philosophical concept. What causes anything? Is it the knife that strikes? The ambulance that arrives too late? Some vulnerability of the victim? The person who encouraged the person who wields the knife? Or the totality of circumstances that led to the event? The criminal law in force in Canada, influenced as it is by  the Enlightenment, is based on a vision of autonomy, agency and individualism  which to this day governs much of our self-understanding. Individual acts are severable from their background conditions, and the consequences of such acts can be imputed to particular individuals. 

Legally speaking, the rule unfolds very physically. The actor who physically intervenes causes even the consequences of his acts that are far greater than initially imagined (again note that the question is not whether the consequences are intended, only whether they are properly described as consequences physically).  In Smithers a kick in the stomach induced death after a rare dysfunction caused vomit leading the victim to suffocate. In Blaue a stabbing induced death after a  refusal on religious grounds by the deceased to receive a blood transfusion. In Towers a blow to the back induced death due to internal bleeding after the deceased’s refusal to receive medical assistance and police agents’ failure to request medical assistance in turn. In all cases the most proximate cause to the deceased’s death, strictly speaking, was distinct from the accused’s doings. Nevertheless the process was initiated physically by the accused. The law tends to make one responsible for one's initially unlawful acts. Metaphorically, the pinball is launched by the accused but he can be said to have caused whatever rebound occurs subsequently.

An instance of this general conception of causality is the “thin skull” doctrine. Smithers is a good illustration here. The deceased suffered from a rare medical condition which triggered his death in unforeseeable circumstances. Medical experts testified to the fact that the cause of his death – asphyxiation by aspiration of vomit – had in their careers never been caused by a blow to the stomach, and even less so to a young person. Nonetheless, the accused was found to have caused the consequences of his acts, because "but for" the initial kick, the death would not have occurred. The death was not an accident but the result of the actions taken by the accused.

Another derivative of this conception arises in the case of an  absence of adequate medical treatment, as enshrined in article 224 Cr.C. Towers and Blaue illustrate the fact that the agent who initiated the physical harm resulting in death due to the lack of appropriate medical treatment – even due to the deceased’s refusal to accept treatment – is responsible.

The limit to this rule is the notion of “novus actus interveniens” –  a new intervening act that breaks the "chain of causality". The word intervene, in French made of “inter” and “venir” – to move physically in between –  connotes the positive nature of the action demanded.  Jordan exemplifies this situation. In this case the initial act posed by the defendant was the stabbing of the deceased, which was nearly healed at the time of his death. The proximate physical cause to his death intervened due to a blatant error in treatment engendering a stark allergic reaction. Had the medical error aggravated the stabbing wound itself the case would have been more difficult to decide. Another example frequently used in civil law but nevertheless applicable in criminal matters is that of an injured patient dying in an ambulance due to a collision. The victim would not be in the ambulance but for the initial harm caused to her by the accused; nonetheless,  the collision of the ambulance on the road is a sufficiently significant event to severe the causal chain.

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