The offence of negligently causing serious injury is created by Crimes Act 1958 s24.
The offence punishes conduct that, if the complainant had died, would have constituted manslaughter by criminal negligence (see R v Shields  VR 717; R v De’Zilwa (2002) 5 VR 408).
While the offence mainly operates in relation to injuries inflicted by motor vehicles, that is not its only field of operation (R v Reid Vic SC 9/10/1996. See e.g., R v Peters  VSCA 222 and DPP v Weston  VSCA 243 for cases where the offence could arise in a non-motor vehicle context).
The offence of negligently causing serious injury has four elements:
The accused owed the complainant a duty of care;
The accused breached that duty by criminal negligence;
The act which breached the duty of care was committed consciously, voluntarily and deliberately;
The accused’s breach of the duty caused the complainant to suffer a "serious injury".
The prosecution does not need to establish that the accused intended to cause serious injury. The test for negligently causing serious injury is objective (Nydam v R  VR 430; R v Shields  VR 717).
The accused owed a duty of care
The first element the prosecution must establish is that the accused owed the complainant a duty of care (Nydam v R  VR 430; R v Shields  VR 717).
Only a legal duty of care can give rise to liability for negligently causing serious injury. Moral duties, such as the obligation to help a stranger in distress or inform emergency services about a fire, are not relevant for this offence (see R v Taktak (1988) 34 A Crim R 334).
One duty which commonly arises is the duty owed by the driver of a motor vehicle to take reasonable care for the safety of other road users (see, e.g., Manley v Alexander (2005) 223 ALR 228).
For more information about when the accused will owe a duty of care, and the content of that duty, see Negligent Manslaughter.
The accused breached the duty by criminal negligence
The second element the prosecution must prove is that the accused breached the duty of care by criminal negligence (Nydam v R  VR 430; R v Shields  VR 717; Wilson v R (1992) 174 CLR 313).
The Court in Aston v The Queen explained how the jury should be directed about this element:
…[T]he judge must direct the jury that the required negligence must be of a high order, involving a great falling short of the standard of care which a reasonable person would have exercised in all of the circumstances, and a high risk that death or serious injury would result from the relevant conduct. The judge should also explain that, since the required negligence must be of a high order, and must involve a high risk of death or serious injury, the kind of negligence which might be constituted by momentary inattention or a minor error of judgment, or which might found a simple civil claim for damages, generally would be insufficient to establish the necessary high degree. It will also be necessary for the judge to point to those matters which might constitute a high order of negligence necessary to support a conviction. The judge should bring home to the jury that the offence is not concerned with minor breaches of the expected standard of care, even if they result in someone being hurt. While minor breaches of the standard of care might establish negligence in a civil case, such minor breaches are not sufficient to establish guilt in a criminal case. More is required, in the sense that the conduct must involve a great falling short of the standard of care, and a high risk that death or serious injury would result. Even a substantial departure from the standard of care may not constitute such a great departure sufficient to constitute criminal negligence (Aston v The Queen  VSCA 225, ).
This is the same degree of negligence required to establish culpable driving by gross negligence (Aston v The Queen  VSCA 225. See also Bouch v The Queen  VSCA 86).
The breach of the duty of care was voluntary
The third element that the prosecution must prove is that the act which breached the duty of care was committed consciously, voluntarily and deliberately (see Ryan v R (1967) 121 CLR 205; Nydam v R  VR 430).
While the prosecution does not need to prove that the accused intended to cause serious injury, they must still prove that the relevant act was committed consciously, voluntarily and deliberately (see R v Haywood  VR 755; R v Vollmer  1 VR 95).
While the law predominantly focuses on the need for an act to be voluntary, there may be cases where the defence argues that an omission is involuntary. In such cases, the judge may need to direct the jury on the need to prove that the omission was conscious, voluntary and deliberate. Alternatively, the judge may identify an act within the omission and may instruct the jury to consider whether the accused committed that act consciously, voluntarily and deliberately.
The breach of the duty of care caused serious injury
The fourth element that the prosecution must prove is that the breach of the duty of care caused the complainant to suffer a serious injury.
As the prosecution must prove that it was the accused’s criminal breach of the duty of care that caused the injury, it is important that the judge precisely identify the allegedly causal act or omission (see Cittadini v R  NSWCCA 302; Justins v R (2010) 79 NSWLR 544).
Where the evidence reveals more than one possible breach of duty, the judge must decide, based on the factual circumstances, whether the separate breaches may be aggregated into a single breach for the purposes of causation (R v Pace & Conduit (Ruling No 2)  VSC 308).