Creating criminal offences
This is a single section from Chapter 24. Read the full chapter here.
On whom should the burden of proof lie?
The burden of proving both the actus reus and the mens rea should remain on the prosecution.
The default position is that the prosecution must prove beyond reasonable doubt both the existence of the prohibited conduct (actus reus) and the requisite mental element (mens rea). This is described as a legal burden of proof. There is no obligation on the defendant to negate those elements of the offence.
If the legislation specifies a justification or excuse (for example, lawful authority or reasonable excuse) for certain conduct, but does not require the defendant to prove its existence, the defendant must raise credible evidence to bring the matter into issue before the court. This is described as an evidential burden—it is not a burden of proof. If the defence satisfies the evidential burden, the prosecution must then disprove the existence of the defence beyond reasonable doubt (the legal burden).
There may sometimes be good policy reasons for placing a legal burden of proof on the defendant. An example is where a strict liability offence is justified (as described in 24.3). In that case, the prosecution must prove only the physical element of the offence and, to avoid liability, the defendant must prove the existence of a statutory defence or total absence of fault on the lesser standard of the balance of probabilities. However, shifting the burden in this way will constitute a limitation on the presumption of innocence (see section 25(c) of the New Zealand Bill of Rights Act 1990) so there must be compelling justification for departing from the default position and consideration must be given to what defences should be available to the defendant.
Legislation must be very clear if it is intended to place a legal burden of proof on the defendant. If the legislation is not clear, the court may interpret the provision as placing only an evidential burden on the defendant.