Most offences criminalise the performance of certain acts, regardless of the consequences of those acts (e.g., rape, theft, trafficking in a drug of dependence). It will generally not be necessary to address the issue of causation when directing the jury about such offences.
However, some offences require the accused’s actions to have led to a particular result. For example, before a person is convicted of murder, their actions must have caused the victim to die. It is in relation to these result-oriented offences that causation may be an issue.
While most of the law in this area has been developed in the context of homicide offences, the principles are of broader application. They will, for example, apply to the offences specified in ss16-18 and 24 of the Crimes Act 1958, which require the accused’s acts to have caused injury or serious injury.
When Does Conduct "Cause" a Result?
For an accused’s conduct to have "caused" a result, it must have "contributed significantly" to that result, or been a "substantial and operating cause" of it (Royall v R (1991) 172 CLR 378; R v Rudebeck  VSCA 155; R v Stein (2007) 18 VR 376; R v Withers  VSCA 306; R v Aidid (2010) 25 VR 593).
The act must be one that an ordinary person would hold, as a matter of common sense, to be a cause of the result. The mere fact that the accused’s conduct contributed causally to a result, or was a necessary cause of the result, is not sufficient (Royall v R (1991) 172 CLR 378).
The accused may be liable for "causing" a result even if his or her conduct was not the direct or immediate cause of that result (Royall v R (1991) 172 CLR 378; R v Withers  VSCA 306; R v Aidid (2010) 25 VR 593).
The accused does not need to be the sole cause of the result. A person can be criminally liable for something that has multiple causes, even if he or she is not responsible for all of those causes (Royall v R (1991) 172 CLR 378; R v Stein (2007) 18 VR 376; R v Withers  VSCA 306; R v Aidid (2010) 25 VR 593).
The accused can "cause" a result by act or omission (Royall v R (1991) 172 CLR 378).
Which Conduct Must Cause the Result?
It is generally not necessary for the jury to determine which of the accused’s acts caused the relevant result, as long as they are satisfied that that result was caused by one of the accused’s acts.
However, in some cases it will be necessary for the jury to determine which particular act caused the relevant result, before they can find the accused guilty. For example, if there are multiple possible causal acts, and the accused’s mental state may have differed when s/he committed those acts, the jury will need to determine which of those acts caused the result – so that they can ascertain whether the accused held the appropriate mental state when s/he committed that particular act (Arulthilakan v R; Mkoka v R (2003) 203 ALR 259; R v McLachlan  2 VR 553).
Similarly, the jury will need to determine which specific act caused the requisite result if the accused may have involuntarily committed one or more of the relevant acts. In such a case, for the accused to be found guilty, the jury will need to be satisfied that s/he voluntarily committed an act that they find caused the criminal result (Ryan v R (1967) 121 CLR 205; R v Butcher  VR 43). See Voluntariness for further information.
Where the offence is one of specific intent (such as murder), the jury must be satisfied that the accused acted with an intent to cause a particular result through that act. It is not sufficient that the accused engaged in the causal act while incidentally possessing the relevant state of mind. For an example of where this principle arose, see Koani v R  HCA 42, where the accused may have shot the deceased due to his negligent handling of a shotgun, and the High Court held that the prosecution could not prove intentional murder by combining the accused’s negligence with an intention to kill.
In some cases the terms of the offence will specify the type of conduct which must have caused the relevant result. For example, the offence of "culpable driving caused by gross negligence" contrary to s318(2)(b) of the Crimes Act 1958 requires the death of the victim to have been caused by a grossly negligent act. It is not enough that the accused was driving in a grossly negligent manner at the time of the death, if that gross negligence was not a substantial and operating cause of the death (R v Feketa (1982) 10 A Crim R 287; R v Heron  VSCA 76).
Difficulties in proving causation may arise if another act or event intervenes between the commission of the accused’s conduct and the criminal result. In such situations, the accused remains liable if his or her conduct is still a substantial operating cause of the result when it occurs. This is because his or her acts or omissions can still properly be said to be the cause of the act, even if some other cause is also operating (R v Evans & Gardiner (No 2)  VR 523; R v Smith (1983) 76 Cr App R 279; R v Aidid (2010) 25 VR 593).
However, the accused will not be liable if his or her conduct is merely the setting in which another cause operates. In such circumstances, the result cannot properly be said to have been caused by the accused’s conduct (R v Evans & Gardiner (No 2)  VR 523; R v Smith (1983) 76 Cr App R 279).
Acts of the Victim
Difficulties in proving causation may also arise if there is evidence that the victim’s own actions were a cause of the result. For example, the victim may injure him or herself while attempting to flee the accused.
In such cases, the accused’s conduct will still be considered to be a legal cause of the result if the victim’s acts were a "natural consequence" of that conduct (Royall v R (1991) 172 CLR 378 per Mason CJ, Deane and Dawson JJ; R v Aidid (2010) 25 VR 593).
Where victims are injured or killed while responding to a threat created by the accused, their actions will only be a "natural consequence" of the accused’s conduct if their fear of the accused was well-founded, and their response to the threat was "reasonable" (Royall v R (1991) 172 CLR 378 per Brennan, Deane, Dawson, Toohey and Gaudron JJ; R v Aidid (2010) 25 VR 593. But see McHugh J and Mason CJ; R v Lee (2005) 12 VR 249).
Failure to Intervene
Difficulties in proving causation may also arise where the consequences of the accused’s conduct could have been averted by the reasonable intervention of either the victim or a third-party.
Australian courts have declined to articulate a special test for these cases. The question for determination is whether or not the accused’s original act or omission remains a substantial, operating cause of the result (R v Evans & Gardiner (No 2)  VR 523).
Content of the Charge
Where causation is straightforward, it may be sufficient simply to instruct the jury that the prosecution must prove, beyond reasonable doubt, that the accused’s conduct caused the relevant result (Royall v R (1991) 172 CLR 378, R v Le Broc (2000) 2 VR 43, R v Ince  VSCA 214).
It will generally be necessary to elaborate upon this direction in more complex cases, such as:
Where the result would not have occurred if the victim or a third party had not committed an intervening act; or
Where the result could have been prevented if the victim or a third party had taken action to avoid the consequences of the accused’s conduct; or
Where one or more of the possible causal acts may have been involuntary (Royall v R (1991) 172 CLR 378; Koani v R  HCA 42).
Directions about intervening acts should ordinarily be made by reference to the facts of the case, rather than being couched in abstract terms (Royall v R (1991) 172 CLR 378).
If it is necessary to direct the jury about the intervening acts of the victim, the jury should generally not be told that the victim’s acts need to be foreseeable. Such a direction is likely to confuse the issue (Royall v R (1991) 172 CLR 378. But see R v Aidid (2010) 25 VR 593).
If detailed directions are given, they should be balanced with an instruction that the question of causation is not a philosophical or a scientific question. It is a question to be determined by the jury by applying their common-sense to the facts as they find them, keeping in mind that the purpose of the inquiry is to attribute legal responsibility in a criminal matter (Campbell v R  WAR 286; Royall v R (1991) 172 CLR 378; R v Withers  VSCA 306).
If a "but for" test is to be incorporated into the directions on causation, care should be taken to ensure that it does not undermine the "substantial cause" direction, thus leading the jury to consider that a negligible cause might suffice (Royall v R (1991) 172 CLR 378; Arulthilakan v R; Mkoka v R (2003) ALR 259).
Causation and Accessorial Liability
Where culpability is alleged to arise by some form of extended accessorial liability, it will generally be necessary to adapt the causation charge. See Part 5: Complicity for further information.
 It should be noted that culpable driving alleged contrary to s318(2)(c) & (d) of the Crimes Act 1958 does not require proof of this same causal nexus: R v Ciantar (2006) 16 VR 26.