Causation can arise in two distinct but related issues:
Did the act of the accused cause the harm the subject of the charge?
Was there an act of the accused that caused the harm?
See the discussion in R v Katarzynski  NSWCCA 72 at .
In (a) there is no dispute as to the act of the accused but the issue is whether it caused the harm occasioned to the victim. In (b) the issue is whether there was any act of the accused that caused the harm occasioned to the victim. In relation to this aspect of causation see Voluntary act of the accused at [4-350]ff.
[2-305] Causation generally
Causation is a question of fact. There can be more than one cause of the injury suffered by the victim. It is wrong to direct the jury that they should search for the principal cause of death: R v Andrew  NSWCCA 310 at .
As to causation generally see: Royall v The Queen (1991) 172 CLR 378 as summarised in Cittadini v R  NSWCCA 302 at –; Burns v The Queen (2012) 246 CLR 334 at –; Reynolds v R  NSWCCA 29 at –; Criminal Practice and Procedure NSW at [6-900]; Criminal Law (NSW) at [CLP.380]ff.
Where appropriate the jury should be directed to consider whether there is any act of the victim that broke the chain of causation between the act of the accused and the injury inflicted upon the victim: McAuliffe v The Queen (1995) 183 CLR 108. In Burns v The Queen it was said at : “Absent intimidation, mistake or other vitiating factor, what an adult of sound mind does is not in law treated as having been caused by another.”
As to cases where the act of the deceased in fleeing the accused resulted in death, see Royall, above, McAuliffe, above, Adid v R (2010) VR 593, R v RIK  NSWCCA 282. In such cases the question is whether the act of the deceased broke the chain of causation by responding to the threat posed by the accused in an unreasonable or irrational manner. Where there are a number of causes of death as a result of more than one life-threatening injury including that allegedly inflicted by the accused or where there have been a number of persons who have inflicted injuries upon the victim the terminology more appropriately used is whether an act of the accused was an “operating and substantial” cause of death: see R v Lam (2008) 185 A Crim R 453. The suggested direction has been framed accordingly.
[2-310] Suggested direction — causation generally
There is an issue as to whether [the accused’s] [acts/omissions] caused the [nature of harm] suffered by [the victim]. The Crown says that [the accused] caused the injury suffered by [the victim] because [indicate Crown allegations]. [The accused] says that you would not be satisfied beyond reasonable doubt that [his/her] [act/omission] caused [the harm] suffered by [the victim] because [set out arguments of the defence].
Whether [the accused’s] [act/omission] caused [the harm] suffered by [the victim] is a question of fact for you to decide. The Crown has the onus of proving beyond reasonable doubt that [the accused] caused the [harm] to [the victim].
In deciding whether the Crown has established this fact to the required degree, you will apply your common sense to all the facts surrounding the infliction of [the harm] to [the victim]. But you should appreciate that you are deciding whether to attribute legal responsibility to an accused person for the harm suffered by another person in what is a criminal prosecution. This is not an issue of philosophical or scientific proof. You are deciding a more practical issue, that is, whether an accused person has committed a crime involving the causing of the harm alleged to another person.
Provided that you are satisfied beyond reasonable doubt that an [act/omission] of [the accused] substantially or significantly contributed to [the harm] allegedly suffered by [the victim], the Crown will have proved this fact. It is not sufficient if the [act/omission] of [the accused] was merely coincidental with the suffering of [the harm] by [the victim] or was insignificantly connected with it. Whether the [act/omission] of [the accused] relied upon by the Crown substantially or significantly contributed to [the harm] suffered by [the victim] is a matter of fact for you to decide on a common sense basis. You must bear in mind, as I have told you, that you are concerned with whether an accused person should bear criminal responsibility for the harm allegedly suffered by another person.
[If appropriate — where evidence of more than one cause of harm
There can be more than one cause for [the harm] suffered by [the victim] that arises from the facts before you. You may find that [the harm] to [the victim] was a result of [list possible causes]. You do not have to determine what, if any, was the major or direct cause of that harm suffered by [the victim]. It is sufficient that you find beyond reasonable doubt that an [act/omission] of [the accused] remained an operating and substantial cause of [the harm] allegedly suffered by [the victim] despite the other injuries suffered by the victim. You make this decision applying your common sense but appreciating that you are concerned with the determination of the criminal responsibility of an accused person for that harm.]
[If appropriate — where it is alleged that the victim had a prior existing physical injury
[The accused] relies on evidence that [the victim] at the time of [the accused’s] alleged [act/omission] suffered from a physical condition of which [the accused] was then unaware … [identify the evidence relied upon by the accused and any evidence on this issue relied upon by the Crown].]
Even if you find that [the victim] suffered from such a physical condition and that [the accused] was not aware of it at the time of the [act/omission] alleged against [him/her], it would still be open to you to find that the Crown has established beyond reasonable doubt that the [act/omission] of [the accused] caused [the harm] allegedly inflicted upon [the victim] provided that [the accused’s] [act/omission] substantially or significantly contributed to that [harm]. The law is that, if a person [does an act/omits to do an act] such as is alleged here, then [he/she] must take or accept the victim as that person was at the time of the [act/omission]. That is to say that an accused person cannot seek to excuse himself or herself from responsibility for the harm inflicted upon another person only because the harm was due to some physical condition or weaknesses from which the victim suffered at the time and of which the accused person was unaware.