What key factor determined X's responsibility in R v. Malcherek; R v. Steel?

In the case of R v. Malcherek; R v. Steel, the key factor that determined X's responsibility was that X's actions directly caused Y's death. This legal principle is rooted in the concept of causation, which is essential in establishing liability in criminal law.

In this particular case, the court focused on whether the defendant’s actions were a substantial and operating cause of the victim's death. The ruling clarified that if the defendant's conduct can be demonstrated to have directly led to the death, they are held criminally responsible. This means that establishing a direct link between X’s actions and the harm that resulted to Y was crucial for determining responsibility.

In contrast, the other options involve aspects that do not directly pertain to the crux of the court's analysis regarding X's liability. The quality of medical intervention and the competence of the doctor can influence outcomes but are secondary to the question of causation. Y's prior health condition might be relevant in discussing the context of Y's overall health but does not negate the direct causative role of X's actions in leading to Y's death. Therefore, the emphasis on causation and direct action establishes why the responsibility was placed on X in this case.