There are two categories of involuntary manslaughter at common law: manslaughter by unlawful and dangerous act and manslaughter by criminal negligence. The authority for the "actus reus" and "mens rea" of involuntary manslaughter by an unlawful and dangerous act is the High Court of Australia case of "Wilson v R". This case determined that the act that caused the death must breach the criminal law and that the act must carry an appreciable risk of serious injury ("actus reus"). Regarding the "mens rea", the court held that the accused must intend to commit the unlawful act and that a reasonable person in the position of the accused would have realised or recognised that the act carried an appreciable risk of serious injury. Manslaughter by criminal negligence, on the other hand, finds its authority in the Victorian case of "Nydam v R", confirmed by the High Court of Australia in "R v Lavender" and "Burns v R". In "Nydam v R", the Court described the office at in the following terms:In order to establish manslaughter by criminal negligence, it is sufficient if the prosecution shows that the act which caused the death was done by the accused consciously and voluntarily, without any intention of causing death or grievous bodily harm but in circumstances which involved such a great falling short of the standard of care which a reasonable man would have exercised and which involved such a high risk that death or grievous bodily harm would follow that the doing of the act merited criminal punishment.