This is a single section from Chapter 21. Read the full chapter here.

When should the person be held responsible?

Legislation must state what mental element must be present for an offence to be committed.


Why and in what circumstances a person should be found guilty of a criminal offence should be considered. This “mental element” (called the “mens rea” or “guilty mind”) can be framed in many different ways (for example, the defendant “intentionally”, “recklessly”, or “knowingly” performed the prohibited conduct). Each of these formulations has subtle differences and is supplemented by the common law.

The default position is that the prosecution must prove the mental element of an offence beyond reasonable doubt. However, in some cases the defendant may be best placed to provide evidence of the mental element. Other strong policy reasons might also exist that justify requiring them to do so. In these cases it may be appropriate to “shift the burden” of proving the mental element from the prosecution to the defence. A common example is strict liability offences in which the prosecution must prove the physical element, but not the mental element, of an offence. The defendant must prove an absence of fault on the lesser standard of the balance of probabilities.

Other formulations exist, such as requiring the prosecution to prove that the defendant “knew or ought to have known” so that a defendant cannot escape conviction just by showing they did not actually know something was happening, or the consequences of an act.

Legislation that imposes a burden on a defendant to prove or establish any element of a defence in criminal proceedings will constitute a limitation on the presumption of innocence (NZBORA 25(c)). Cogent reasons will therefore be required to justify shifting the burden.

Strict liability offences are commonly used in the regulatory context and may be appropriate where:


  • the offence involves the protection of the public, or a group such as employees, from those who voluntarily undertake risk-creating activities;
  • there is a need to incentivise people who undertake those activities to adopt appropriate precautions to prevent breaches;
  • the defendant is best placed to establish absence of fault because of matters primarily within their knowledge.


Legislation that imposes any burden of proof on a defendant in criminal proceedings should explicitly address:


  • who the burden rests with;
  • what matters they are required to prove;
  • the standard of proof that applies to those matters (usually “the balance of probabilities”).

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