Knowledge, belief, and recklessness in criminal law

Are the courts too willing to use an unsound definition of the mens rea requirement of knowledge?

A workable definition of knowledge is belief that is true. This has been used in cases and legal texts: for example, AP Simester and WJ Brookbanks, Principles of Criminal Law(4th ed, Brookers, Wellington, 2012) at [4.5]; David Ormerod, Smith and Hogan’s Criminal Law, (13th ed, Oxford University Press, Oxford, 2011) at [5.25]–[5.27], both cited in R v Banks [2014] NZHC 1244 at [39]. However, knowledge is more complex a concept than that, as discussed by Bertrand Russell in Chapter 13 of his The Problems of Philosophy (1912), which is freely available at A person does not really know something if the justification (that is, the reason) for the claimed knowledge, is false. Russell’s account of knowledge can be read with Edmund Gettier’s famous and brief 1963 paper “Is Justified True Belief Knowledge?”, available at, which has generated a large body of entertaining discussion.

A true belief is not knowledge when it is deduced from a false belief. For example, the defendant may say, “I knew it was cocaine because it was some of what John gave me”, when in fact it was cocaine given to the defendant by someone else. The defendant believed that it was cocaine, on grounds that might have been strong if they were true. The reasonableness of the grounds depends on the likelihood of John having supplied the drug. If the grounds were weak, it would be more accurate to say that the defendant merely suspected that the drug was cocaine. This illustrates how a defendant may wrongly claim to have known something when it was only believed or suspected. True belief is also not knowledge if it is arrived at by fallacious reasoning. The defendant may claim to have known that a substance was cocaine because John supplies cocaine and John supplied this substance. The fallacy is that John may also supply other substances. Although the substance was indeed cocaine, the defendant’s belief would not normally be described as knowledge because it was a product of the mistaken assumption. The defendant had a belief, perhaps a belief on strong grounds if John nearly always supplied cocaine, but although the defendant thought it was knowledge, it was really just probable opinion. But if probable opinion is sufficiently probable to result in a firm belief, it can be correct to call it knowledge. This is different from the lesser probability required, for example, for the familiar “reasonable grounds to believe” needed in the search context, where an applicant for a warrant need only have the belief, not knowledge, that the relevant thing is at the place to be searched.

If a defendant admits in a police interview to having had knowledge of circumstances which were required to exist for there to be an actus reus, the police would be unlikely to challenge the defendant’s grounds for that claim of knowledge. But in the interval between interview and trial, when there would usually be some opportunity for philosophical reflection, a defendant may realise that the circumstances were more uncertain than they were thought to have been, and that the claim of knowledge was an exaggeration. This defendant may decide that what was perceived was a probability, not a certainty, and that the state of mind was suspicion rather than belief.

However, the law does tend to conflate the concepts of knowledge and belief. Whether it is correct to do so may be questioned. For example, see Kerr v R [2012] NZCA 121, which concerns knowing a purpose of future use of the relevant thing. The court, by interpreting knowledge as including belief (or, more accurately, as including belief that was false), in reality read in to s 12A(1) of the Misuse of Drugs Act 1975 the phrase “or believing”, referring to common law instances of knowledge being equated with belief (at [14]-[16]), the definition in the New Zealand Oxford Dictionary ([17]), and perceived difficulties with excluding belief ([18]-[19]). With respect, it should be noted that online Oxford dictionary definitions of  “know” do not refer to belief, and definitions of  “believe” do not refer to knowledge. Further, the Court’s difficulty with the concept of knowing a future event is beside the point, because what s 12A requires is knowledge of a present purpose (“is to be used”). The cases cited are from other contexts, but relevantly include where a substance was supplied to an undercover officer who had no intention of using it illicitly – raising the unaddressed issue of whether an investigatory technique should influence the definition of an offence – or receiving, where it was thought necessary to read in belief if knowledge was limited to what the defendant actually saw. This ignores the wider dictionary definition of know as to be aware of through observation, inquiry, or information. The real difficulty in Kerr was that Parliament had not anticipated that the police would use undercover officers to pretend to defendants that they were going to put items to illicit use, and the legislation should have specified “knowing or believing” in defining the mental elements of the offence.

Those matters aside, it may be that recklessness, which requires, as one of its elements, perception of a risk of the relevant criminality occurring if the defendant acts, is not amenable to the Russell – Gettier analysis. It is the perception, not the grounds for the perception, of the risk, that matters here. For the purposes of attributing criminal responsibility, where attention is on the harm threatened by the defendant, it is the perceived risk, not a known risk, that is a component of recklessness. The defendant’s perception of the probability of the relevant criminal outcome is sufficient, and if “knowledge” of the risk is referred to, it should be understood here in the loose sense of risk perception.