Saturday, December 22, 2018

Fair process and choice of mode of trial

In S(SC 36/2018) v R [2018] NZSC 124, (the Court of Appeal decision is noted here on 5 May 2018) the defendant had not been told that a judge-alone trial was available, and he was convicted following trial by jury.

The Supreme Court delivered two judgments: William Young, O’Regan and Ellen France JJ jointly (delivered by Ellen France J, paras [1]-[86]), and a concurring judgment by Glazebrook and Arnold JJ (delivered by Glazebrook J, paras [87]-[99]). The appeal was dismissed.

The error was not jurisdictional ([46], [91]), for the court had jurisdiction to try the charges by either mode, and the error did not render the jury trial a nullity. It was a procedural error, and the issue on appeal was whether it had rendered the jury trial unfair. Was it unfair to try the defendant by jury, when he had not been aware of his right to a judge-alone trial?

The jury trial had been conducted fairly ([34], [96]). The defendant would have been advised to elect trial by jury ([54], [98]). There was no reason to think this was unsound advice ([56]). He had not demonstrated that he would have rejected that advice at the time it was given. On these facts there was nothing to suggest that an unfair procedural course had been taken ([83], [98]).

On different facts, if a defendant had been unaware of the right to elect trial by jury, that would amount to loss of an important statutory right, and such an error might, depending on the circumstances, amount to an unfair process rendering the judge-alone trial unfair ([99]).

So there could be circumstances where absence of advice on election of mode of trial would result in unfair process, but those did not exist in the present appeal ([96]).

There are some areas of vagueness. As far as nullity is concerned, a threshold is mentioned ([45]-[46]). This suggests some flexibility in the concept of nullity, and the cases cited indicate differing approaches and various circumstances. Nothing was resolved about that in this appeal, so the references to some of the other cases could be called excessive and perhaps even confusing. Cases interpreting different legislation need to be shown to be relevant, and older references to the overlapping of nullity and miscarriage of justice, and to degrees of nullity, do not seem relevant to s 232 in which attention is confined to three alternative ways in which a miscarriage of justice may occur: where there is a real risk that the outcome of the trial was affected, or where the trial was unfair, or where the trial was a nullity. Too much discussion of authorities calls to mind the amusing confession of having heard, “second hand”, that “a former clerk once referred to one of my judgments as ‘over-researched as usual’”: see Justice Susan Glazebrook, “Academics and the Supreme Court” (2017) 48 VUWLR 237 at 239. In this case it's the other judgment that seems rather overwrought.

Thursday, December 13, 2018

Case Note: Onus and standard of proof that evidence was improperly obtained: Kearns v R [2017] NZCA 51, [2017] 2 NZLR 835

Criminal lawyers in New Zealand are familiar with s 30 of the Evidence Act 2006 which concerns the admissibility of improperly obtained evidence. Its first two subsections are as follows, and this note focuses on (2)(a):

(1) This section applies to a criminal proceeding in which the prosecution offers or proposes to offer evidence if—
(a) the defendant or, if applicable, a co-defendant against whom the evidence is offered raises, on the basis of an evidential foundation, the issue of whether the evidence was improperly obtained and informs the prosecution of the grounds for raising the issue; or
(b) the Judge raises the issue of whether the evidence was improperly obtained and informs the prosecution of the grounds for raising the issue.
(2)The Judge must—
(a) find, on the balance of probabilities, whether or not the evidence was improperly obtained; and
(b) if the Judge finds that the evidence has been improperly obtained, determine whether or not the exclusion of the evidence is proportionate to the impropriety by means of a balancing process that gives appropriate weight to the impropriety and takes proper account of the need for an effective and credible system of justice.”

On the issue of whether the evidence in question was improperly obtained, is there an onus on any party, and is there a standard to which the issue must be decided? The distinction between the terms onus and standard must be borne in mind. An onus, or as it is also called, a burden, is on the party that has an obligation to prove something. A standard is the level of proof or satisfaction required to be established by the party having the onus. On the ultimate issue of guilt in criminal cases, the onus or burden is (usually) on the prosecution and the standard is beyond reasonable doubt. Where admissibility is in issue, the decision may involve both determination of facts – a matter of proof – and consideration of those facts to decide whether impropriety existed – a matter requiring an evaluative assessment.[1]While there have been dicta[2]that suggest that it is not appropriate to apply a standard to the exercise of judgement, subsection (2)(a) seems plainly to apply the standard of the balance of probabilities to whether, as a matter of judgement, proved facts establish impropriety. Both the determination of the facts, and the evaluation of them, are subject to this standard.

Ordinarily, the party that asks the court to do something has the onus of satisfying the judge that it should be done. And ordinarily, technical legal terms have their usual meaning. So on first blush it would seem that the defendant (or, if applicable, a co-defendant) who asks the court to exclude evidence which is otherwise admissible, on the grounds that it was improperly obtained, has the onus of persuading the court that the evidence was improperly obtained. The standard is said to be on the balance of probabilities.[3]Even if it is the judge who raises the issue, the onus and standard should not change.

But in this context the phrase “on the balance of probabilities” could mean “on the preponderance of probabilities”. Here, preponderance means one scenario is more likely than the other, including where one reaches the balance of probabilities fixed standard, but also including cases where the more likely scenario is nevertheless below the balance of probabilities standard. This extended meaning of preponderance can be relevant because the judge is forced to make a decision. Whichever of the alternative scenarios is the most probable wins, even if both are less likely than not. In cases that may occur only relatively rarely there is another problem: what should the decision be if there is no reason to prefer one version of the facts to the other? Both versions may appear reliable, or they may seem equally unreliable. Here there is no preponderance of probabilities, and commentators have called this the equilibrium problem. A sensible solution to such a problem would be to refer to the onus of proof: equilibrium means the party with the onus has failed to persuade the judge to rule in its favour. So, does the absence of reference in s 30(2) to an onus mean there is no onus, or is an onus implied? And if an onus can be implied, is it always on one party, or can it shift depending on what the judge perceives as the justice of the case?

At an early stage commentators thought there was no onus, and that therefore equilibrium was a problem.[4] Priestley J recognised this in R v Hanford,[5]a case where the witnesses on each side seemed equally credible. The obligation to make a decision without an onus to resolve the equilibrium led his Honour to observe that this legislative framework infringed “the constitutional right of a judge, in rare cases, to be unsure”. If one respectfully doubts that there is such a constitutional right, preferring to say that litigants have a right to have judges decide their issues, it could still be said that a legislated requirement for a finding, in the absence of an onus, is an interference with the independence of the judiciary, even, in cases of equilibrium, to the extent of potentially requiring dishonesty. Certainly it is acceptable, and common, for the legislature to tell judges what matters to take into account, and even what matters are important, but what Priestley J found objectionable was the forcing of a judge to make a decision, in circumstances where a decision couldn’t be made.

In the light of this difficulty it would be worth re-considering the interpretation of these subsections. This is not to say that these issues matter in most cases, where decisions are relatively easy and outcomes would be the same regardless of onus, balance, and the imperative to decide. Many cases almost decide themselves, at least on the issue of impropriety, and it is not unusual for prosecutors to concede the point as a preliminary to contesting the balancing decision of admissibility.

In Kearns v R[6]the appeal against a ruling that evidence obtained in a vehicle search was admissible was allowed to the extent that the issue of admissibility was remitted to the District Court for further examination of the evidence and further findings of fact. This was necessary because the judge had failed to fully examine the lawfulness of the search and the extent of impropriety. The Court of Appeal’s mention of the issue of onus was therefore cursory, particularly because the Court was discussing the rather more interesting issue of the risk that the initial approach by the police was racially motivated. It was noted at [40] that, “Once a foundation is established, subs (2)(a) obliges the court, ideally with the assistance of counsel, to elicit the evidence necessary for a finding to be made.” At [37] the Court rejected a submission that it was for the prosecutor to prove that the search was lawful, once the issue was raised:

“The legislative history of s 30 demonstrates that Parliament specifically rejected imposing the burden of proving propriety on the prosecution. Parliament chose not to follow the Law Commission’s proposed draft in that respect ... . The correct approach is that neither party carries the onus. Onus of proof language does not make sense where the judge has a duty to make a positive finding. The judge must choose, as best he or she can on the evidence, which of the scenarios (proper or improper) is the most probable and make a finding accordingly. ....” [footnote omitted]

In the context of ordinary principles of interpretation, and of Hanford and similar cases, it is not controversial that the prosecution does not (always) have the onus of proving propriety. What stands out, however, is the claim that “Onus of proof language does not make sense where the judge has a duty to make a positive finding.” One would have thought, with respect, that an onus is particularly relevant where a finding has to be made, especially in those difficult cases of equilibrium. Perhaps the Court meant to say, “Standard of proof language does not make sense where the judge has a duty to make a positive finding”, which would be true but this revision does not fit the context. Be that as it may, the Court went on to emphasise that a choice must be made, as best as it can be, between the scenarios. One alternative must be more probable than the other, regardless of any standard. This seems to amount, in those difficult cases, to forcing a fiction of unequal likelihoods on the judge. Further, it requires the judge to conclude that evidence was improperly obtained just because that is the more probable scenario, even if the probabilities of each scenario are well below the standard of the balance of probabilities. The Court may have been taking the phrase in (2)(a), “on the balance of probabilities” to mean “on the preponderance of probabilities”.

It is respectfully suggested that the ordinary interpretation, mentioned earlier in this note, is to be preferred. It conforms with common sense as to onus, it applies the usual meaning of the balance of probabilities as a standard rather than a preponderance, it does not involve an equilibrium problem, it does not impose a fiction on judges, it does not compromise judicial independence, and it does not require highly unlikely allegations of impropriety to be accepted. If, however, a permanent onus on the defendant who seeks to have evidence excluded is thought to go too far, it can still be noted that the legislature’s refusal to place a universally applicable onus on the prosecutor, coupled with the silence of the provisions on the question of onus, does not exclude the use of an onus as the judge sees fit in the circumstances of a particular case.[7] 

[Update:] A shifting onus is consistent with the phrase in (2)(a), “whether or not”, which allows for the possibility that the prosecutor may succeed in satisfying the judge on the balance of probabilities that the evidence was not improperly obtained. The Law Commission has noted opinions to the effect that s 30 is biased towards holding improperly obtained evidence to be admissible, and has referred in this context to the equilibrium problem as illustrating that the party with the burden of proof (assumed to be the defendant) may fail to meet the standard of the balance of probabilities[8]. This appears to overlook the argument presented here.

[1] The phrase “evaluative assessment”, is used in Marwood v Commissioner of Police [2016] NZSC 139, [2017] 1 NZLR 260 at [46] to describe the process of assessing the appropriateness of a remedy for unreasonable searches, distinguishing it from the exercise of a discretion. Illustrations of the use of evaluation include assessing whether rights have been waived in the context of police interviews: Perry v R [2015] NZCA 530 at [32], the decision by a jury on the significance of propensity evidence: R(CA477/2014) v R [2015] NZCA 394at [23], [29], and the choice of an appropriate sentence: R v Cunnard [2014] NZCA 138 at [13]. An appeal against an evaluative assessment may involve the appellate court substituting its assessment for that of the court below. Where the basis for alleged impropriety is unfairness in the way the challenged evidence was obtained (s 30(5)(c)), an evaluative assessment will be required, as is illustrated on appeal in King v Police [2018] NZHC 1213 at [27]-[34] concerning a breach of the rules for taking statements, and in R v Alsford [2017] NZSC 42, [2017] 1 NZLR 710 at [38] as to breach of privacy.
[2] For example, R v Leitch [1998] 1 NZLR 420, 428, (1997) 15 CRNZ 321, 327 (CA) referred to in Simon France (ed) Adams on Criminal Law – Evidence (online looseleaf ed, Thomson Reuters) at ED2.02(2). The evaluation for impropriety can be straightforward, for example evidence obtained in an unlawful search will usually be obtained improperly, except where the unlawfulness is minor or technical: R v Williams [2007] NZCA 52, [2007] 3 NZLR 207, (2007) 23 CRNZ 1 at [21]-[23]. Often, a breach of the law can be established by proof of facts and without a further process of evaluation, but where reasonableness has to be assessed, for example in considering the adequacy of grounds for an action, evaluation will be necessary.
[3] The expression “the balance of probabilities” is discussed extensively in Z v Dental Complaints Assessment Authority [2008] NZSC 55. It is not a flexible standard (per Elias CJ at [28], Blanchard, Tipping and McGrath JJ at [101], Anderson J “largely in agreement” with the joint judgment [146]), and it means more likely than not (per Elias CJ at [28], joint judgment at [102]).
     Mahoney et al, The Evidence Act 2006: Act and Analysis (2007, Brookers Ltd) at EV 30.06(1). The passage in Adams on Criminal Law – Evidence, above note 2, at EA30.06(1) has been to similar effect.
[5] R v Hanford HC Auckland CRI-2007-057-1922, 24 July 2008 at [8].
     Kearns v R [2017] NZCA 51.
[7] Flexibility is apparent in pre-Kearns dicta. In R v Follas HC Rotorua CRI-2009-077-1516, 22 November 2010, at [37] Wylie J noted and agreed with Priestley J in Hanford at [82]-[84] (including the observation that s 30(2) is ambiguous on whether the defendant, or neither party, bears an onus), and considered that the onus should be on the prosecutor (at [38]). This was noted in, and is inconsistent with, Kearns (at [37]). It may be that in Kearns it would be easier for the prosecutor, than for the defendant, to establish why the police approached the car.

     NZLC R142 The Second Review of the Evidence Act 2006 (28 February 2019), p 134 at [7.52] and footnote 43.

Wednesday, October 10, 2018

Reflections on Lundy

Good to see the Court of Appeal’s judgment in Lundy v R [2018] NZCA  410 (9 October 2018) delivered at last.

It’s one of those “world-famous-in-New Zealand” things: a double homicide that was always a whodunit. I don’t comment on the decision, because the case may not be over.

Some points do occur to me, however.

The appeal was determined under the old criteria for deciding conviction appeals (the new ones are here). Would the decision have been the same under the new law? Are the approaches in Bain and Matenga the same? See my notes of 11 May 2007  here and here9 July 2009 here, 20 July 2009 here.

To what extent would this illustration of the way conviction appeals are decided influence the future Criminal Cases Review Commission (CCRC) in its decision whether to refer cases to an appeal court? The current Bill proposing the establishment of the CCRC is here, and the referral criteria are in clause 17.

How appellate courts should approach conviction appeals is surprisingly unclear. Today the High Court of Australia corrected the Supreme Court of Western Australia on this: Rodi v Western Australia [2018] HCA 44 at [37], and, also today, the New Zealand Supreme Court granted leave to appeal on whether a conviction appeal after a judge-alone trial requires the appellate court to adopt a review approach or to substitute its view of the evidence for that of the trial judge: Sena v Police [2018] NZSC 92 (leave granted).

[Update: On 6 May 2019 the Supreme Court granted Mr Lundy leave to appeal: [2019] NZSC 45. Leave was limited to the proviso issue. We will have to wait to see whether there was an error made by the Court of Appeal insofar as it may have failed to consider the cumulative effect of the - admittedly, individually weak - inferences that could have supported the defence case. Could they, in combination, have raised a reasonable doubt? On this point we may recall how the reasoning of Ian Binnie in the Bain compensation case was criticised for (allegedly) not considering in combination points that supported the Crown's case. Place your bets. As any Bayesian bookie will tell us, if - for the sake of argument - a reasonable doubt exists when P(G) = 0.94 or less, then to move from a prosecution case that established guilt to P(G) = 0.99 to get to a reasonable doubt, you would have to accept defence evidence which, taken overall, was at least 6 times more consistent with innocence than with guilt. On the fairness side of the coin, broadly speaking, the issue would be whether there was a real risk that the wrongly admitted scientific evidence affected assessment of the probative value of the other evidence in a more than trivial way, by causing the jury to over-estimate the probative value of the evidence against the defendant or to under-estimate the probative value of the evidence that favoured the defendant.]

[Another update: after the Supreme Court delivered its judgment, I discuss the outcome here.]

Tuesday, September 25, 2018

When "must" a jury find a defendant guilty?

It is wrong for judges to compose, for use by juries in reaching verdicts, question trails that include directions that a verdict of guilty must be returned. For example, a question might take the form, “if [this question is answered “yes”] find the defendant guilty.”

Why is this wrong? A jury may be told when they must acquit, but never that they must convict. This is a safeguard against unconscionable prosecutions, where, although strictly speaking, the jury might be satisfied that the prosecutor has proved all the necessary elements to establish guilt, nevertheless it would be morally wrong to find the defendant guilty. The safeguard is so important that it is sometimes described as having constitutional importance. I have discussed this on 20 December 2013, here, and see also my note of 27 October 2006, here.

Yet it is wrong, at common law, to mention this option to the jury. Counsel cannot ask the jury to ignore the law. The law allows, but does not refer to, conscience verdicts. The subject belongs to jury-room discussion, into which a court will not inquire (as distinct from some aspects of jury-room discussion that might be the subject of judicial inquiry, for example to ascertain whether the jury has been improperly influenced).

Little appears to be known at the bar about conscience verdicts. [Update: see the references in S (SC 36/2018) v R [2018] NZSC 124 at [76], noted here on 22 December 2018.] For example, in De Soto v R [2018] NZCA 366, where the appeals were properly dismissed, no one raised the issue about the form that the question trail had taken. I do not suggest that any consequence followed from this in the circumstances of this case, as there does not appear to be anything about it that would raise a moral question about the appropriateness of findings of guilt. So the omission was not an error, and counsel may well have considered the point but correctly decided not to raise it in this particular appeal.

I just have a niggle with the question numbered 8 in [15] of De Soto: why is the instruction, in the event of an affirmative answer, to go on to question 9? The questions follow those set out in Ahsin v R [2014] NZSC 153 at [140], but they are put in the way designed to emphasise the Crown's burden and standard of proof. Ahsin requires a reasonable possibility that each of the following exist: demonstration of withdrawal, steps to undo encouragement, those steps being all that reasonably could have been done, and those reasonable steps having been taken in a timely way. Absence of a reasonable possibility that any one of these requirements has been met is sufficient for the defence to fail.

Also of interest in De Soto is the availability of the defence of withdrawal when a defendant is charged with importation of a drug, notwithstanding that the defendant may have been a principal offender through instigating the importation by placing an order with an overseas supplier.

Wednesday, August 29, 2018

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.

Friday, July 06, 2018

Take a coin, any coin

It is good to see an article on Bayesian reasoning with conditional probabilities in the current issue of the Times Literary Supplement: “Thomas Bayes and the crisis in science” by David Papineau (June 28, 2018).

As Professor Papineau points out, Bayesian analysis is used in many fields, including law.

One of the difficulties in discussing Bayesian reasoning, or indeed any complex subject, is that clear and simple points can become obscured by technical terms.

It took me a while to get to grips with Professor Papineau’s coin-tossing illustration. What it is designed to illustrate is an error of reasoning that is, apparently, found in too many published scientific studies. Essentially, the error involves drawing a conclusion from too little information. But Professor Papineau's illustration is of one test, not of an experiment involving a statistically significant number of test results.

If you take a coin – any coin – and toss it five times, and if you get five heads, how likely is it that the coin is biased? Pretend that you do not have special coin-tossing skills that allow you to determine the result of a toss. Also pretend that it doesn't occur to you to just keep tossing the coin to see what proportion of the sequences of five-tosses give results of five-heads.

After only a little reflection you realise that an unbiased coin will, on average, produce five-heads once every 32 times the five-toss sequence is carried out. One in 32 gives a probability of 0.03, approximately. The probability of getting five-heads from an unbiased coin looks very low, and you might be tempted to conclude that, therefore, there is a probability of 0.97 that the coin is biased.

Apparently, a significant number of scientific studies have been published in peer-reviewed journals, reporting conclusions arrived at through that sort of reasoning.

Bayesian analysis, if you are able to do it, will quickly show you that such conclusions are ridiculous, or, as Professor Papineau says, “silly” or “nonsense on stilts”.

If you are a lawyer, you might have to convince a judge or jury that an apparently obvious conclusion, reached by a respected expert, is wrong. It is far from easy to do this, and that may be why Bayesian analysis is taking so long to be routinely applied in courtrooms.

Fundamentally, the probability of getting five-heads if the coin is not biased, is not the same as the probability of the coin not being biased if it produced five-heads. The probability of A, given B, is not the same as the probability of B, given A.

My favourite way of illustrating this is to say: the probability of an animal having four legs, given that it is a sheep, is not the same as the probability of it being a sheep, given that it has four legs. The first tells you something about sheep, the second something about quadrupeds.

We know something about an unbiased coin: about three per cent of the times it is tossed five times it will produce a sequence of five-heads. But what do we know about a coin that has produced a five-head sequence? Is it biased or unbiased? If it is biased, how biased is it? Does it always produce five-heads or only some proportion of the times it is tossed five times? Is a biased coin commonly found or is it rare? Those things need to be known in calculating the probability that the tossed coin which produces a five-head sequence is biased.

At the risk of over-explaining this, let’s ignore - just for a moment - the rarity of biased coins and consider possible results of 100 five-toss sequences for a biased, and an unbiased, coin:

                                    Biased             Unbiased
            Five-heads       25                      3
             Other               75                     97

These results give three per cent of the results for the unbiased coin showing five-heads. The biased coin was, in this example, biased in such a way that it showed five-heads 25 per cent of the time and any other result 75 per cent of the time. So, of the five-heads results, three were from the unbiased coin and 25 from the biased coin, so the percentage of five-heads results that were from the biased coin is 25/28 times 100, or 89.3 per cent. Assuming you were equally likely to have tested either of the two coins, the probability, after one five-toss of the coin sequence, of the tossed coin being biased, given the five-head result, is approximately 0.89, which would not be regarded scientifically as significant proof of bias. Conventionally, for a significant conclusion that the coin was biased the conclusion could only be wrong no more than 5 per cent of the time.

This is not to say that the result is of no use. It does tend to prove the coin is biased. The strength of its tendency to prove bias is the likelihood ratio: the ratio of the probability of five-heads, given the coin is biased (from the above table this is 0.25) to the probability of five-heads, given the coin is unbiased (0.03), a ratio of 8.3 to 1. On the issue of bias, the result should be reported as: whatever the other evidence of bias may be, this result is 8.3 times more likely if the coin is biased than if it is not biased. The other evidence may be from a survey of coins which measured how often we can expect to find biased coins.

Now suppose that such a biased coin is only found once in every ten thousand coins, and that all biased coins have the same bias. The probability of a randomly chosen coin you have tossed and got a five-heads result being biased is, when you do the calculation using Bayes' formula, 0.0008. Eight occurrences in ten thousand. Much lower than the 0.97 probability (97 occurrences in 100) of the coin being biased that might have been reported in a peer-reviewed journal.

Again, this is not as surprising as it may seem at first glance. There may be only one biased coin in 10,000 coins, and one occurrence of five-heads from a biased coin in 40,000 coins (using the one-in-four frequency in the table), but, in round figures, there will also be 1200 occurrences (three per cent) of five-heads from unbiased coins in those 40,000 coins. This is why, on this occurrence of biased coins, a five-head result is much more likely (1200 times more likely) to be from an unbiased coin than from a biased one.

Only a very brave judge or juror would bet a significant sum that a coin which when tossed produced a five-head sequence was not biased. The bets would go the other way and those significant sums would most probably be lost.

And, as an afterthought: if you feel estimating prior probabilities is a bit haphazard, the Bayesian formula can be turned around to tell you what priors you would need in order to get in the above example P(the coin is biased) = 0.95. You would, before doing the experiment, need to be convinced to a probability of about 0.70 that the coin was biased. This sort of approach is discussed in a paper by David Colquhoun (available courtesy of The Royal Society Publishing). If, as a lawyer, you want an easy introduction to Bayesian reasoning, see my draft paper on propensity evidence.

Friday, June 22, 2018

Lane v The Queen: error classification and a nudge for Weiss

Good to see Weiss v The Queen (2005) 224 CLR 300 getting another nudge into the obscurity it so richly deserves, in Lane v The Queen [2018] HCA 28 (20 June 2018).

Lane raises, for reflective readers, the difficulty of distinguishing trial errors that go to what Australians call the presuppositions, and errors that are less fundamental but which nevertheless require the quashing of a conviction.

The point of trying to distinguish these types of errors from each other is that when the former occur there is no need for an appellate court to ask whether the verdict could have been affected by the error, whereas when the latter occur the appellate court asks itself whether there is a real risk that the verdict would have been more favourable to the defendant (appellant) if the error had not happened.

Presuppositional errors require quashing of convictions, whereas other errors (beyond the trivial or irrelevant) raise the “real risk” question.

It is probably not inaccurate to think of presuppositional errors as those which undermine the fairness of trials. In Lane, the joint judgment of Kiefel CJ, Bell, Keane and Edelman JJ treats the error as presuppositional: the jury had not been told that unanimity on a particular factual issue was, in the circumstances of the case, required. While recognising the limited utility of classifications of errors, the joint judgment says that it does put the focus on the effects of the errors (at [46]), and that here the misdirection was apt to prevent the performance by the jury of its function of reaching a unanimous verdict. This required, without further inquiry, the quashing of the conviction.

We could say that a trial resulting in a verdict that did not comply with the law was not a fair trial.

The other view of the error in Lane was taken by Gageler J, who agreed with the orders made in the joint judgment. Here, the question was simply whether the possibility of lack of unanimity was more than theoretical (at [58]). In the circumstances, it could not be said that without the error the jury would have returned the same verdict (at [63]).

The joint judgment does not engage with Gageler J’s approach, so without an explanation for why it is wrong it has more weight than it would otherwise have. Even so, Lane is authority for the proposition that where the circumstances of a case are such that a jury may not have been unanimous on an issue where unanimity was required, a resulting conviction will have to be quashed.

My opening and scornful remark about Weiss is addressed to its endorsement of the appeal-judges-as-jurors view of what an appeal court can do. I am one of those who think that appellate judges should never make determinations of guilt. Their function is to assess whether there is a real risk that a verdict more favourable to the defendant (appellant) would have been returned if the error had not occurred, or whether the trial was unfair or was a nullity.

There are some comments in Lane which reject the notion of appeal judges as triers of fact, but those comments need to be read in the context of Lane. So, in that context, Weiss has received its nudge.

Update: The day after Lane was delivered, the New Zealand Supreme Court decided that an error at trial resulting in the jury being instructed incorrectly on mens rea elements required the appellate court to apply the “real risk” analysis, and made no reference to the more fundamental trial fairness ground. Readers are not, therefore, assisted in discovering why this was not a fairness issue. The decision is currently subject to suppression orders, so is only available to people who have access to the databases: [2018] NZSC 56.

Wednesday, May 16, 2018

Reviewing the Evidence Act 2006

Well jurists, it’s only a month to go before your submissions on the New Zealand Law Commission’s Second Review of the Evidence Act 2006Issues Paper 42, are due in.

You don’t have to answer all questions, so you can focus on your favourite topics.

Mine are done, as you can see.

[Update 13 March 2019: the Commission has published its review, available here.]

Saturday, May 05, 2018

An admirable dissent

On rare occasions you read a dissenting judgment that is reasoned with such brilliant clarity that you may bruise your hands in applauding.

So it is with S (CA377/2017) v R [2018] NZCA 101 (19 April 2018).

Counsel had not told the defendant that there was the option of having a judge alone trial (JAT) and, without consulting the client on the matter elected jury trial on his behalf.

After being convicted at trial the client became aware that he could have had a JAT, and deposed that he would have chosen that mode of trial if the matter had been discussed with him.

What was the status of the error? Under s 232 of the Criminal Procedure Act 2011, if it rendered the trial unfair it would be unnecessary to show that it had affected the outcome of the trial.

The majority two judges of the Court of Appeal held that the error did not render the trial unfair, and this was the point on which one judge dissented.

In the absence of local case law, the majority were guided by the Supreme Court of Canada in R v Turpin [1989] 1 SCR 1296, the Supreme Court of the United States in Singer v United States 380 US 24 (1965), and the High Court of Australia in Brown v R (1986) 160 CLR 171.

This led to the position that, as there was no “right” to a JAT, but only a right to elect jury trial (with JAT being the default position – what one might think of as the factory setting), the trial was not unfair in terms of s 232(4)(b). Patience with subtlety is necessary to follow the reasoning.

Nor, said the majority, was the error fundamental because it had not been included in a list of fundamental errors compiled in an earlier decision of the Court. (But, as the dissenter observed, neither had it been specifically excluded.)

And there was nothing to indicate that the error had affected the outcome of the trial.

It would be wrong for counsel to rely on the majority judgment as permission to avoid taking instructions on election of jury trial whenever there is a choice to be made, pending resolution of the issue in the Supreme Court (in this or a similar case). The Court certainly did not intend to give permission to make errors.

The dissent essentially takes the position that, just as it would be a fundamental error to fail to inform a defendant of the right to elect jury trial, so too is it a fundamental error to fail to inform a client of the option of judge alone trial. It fits with other fundamental errors identified in Hall v R [2015] NZCA 403 at [65]: decisions as to plea, giving evidence, and presenting a defence, and with the duty referred to at [71].

There was no doubt that the jury trial that happened in this case was in its substance fair. What s 232(4) relevantly requires, to amount to a miscarriage of justice, is an error in relation to the trial that resulted in an unfair trial. An “unfair trial” is not defined, but there could be two types of unfairness: substantive and procedural. Is a trial procedurally fair if it proceeds in a mode that was not, when there was a choice, chosen by the defendant?

Another, and probably better, way of looking at this is to ask whether the error rendered the jury trial a nullity. Is the defendant's decision a jurisdiction-creating act? The default mode of trial, judge-alone, occurs without a decision from the defendant, and the jury mode is only activated by the defendant's election. This legislative scheme is consistent with jurisdiction to have a jury trial being created by the defendant's act, and such a trial being a nullity in the absence of such act. At this point you may well be asking, "But Don, what about the Kable case you discussed here on 7 June 2013?"

Update: on 30 July 2018 the Supreme Court granted leave to appeal on the question whether the Court of Appeal was right to dismiss the appeal on the mode of trial point: [2018] NZSC 64, and on 20 December 2018 the Court dismissed the appeal: S (SC 36/2018) v R [2018] NZSC 124, noted here.

Thursday, April 12, 2018

Coming to law from science

“Chief Justice French’s background in science has been useful in expressing ideas. He has suggested that identifying elements of administrative justice is “a little like the identification of ‘fundamental’ particles in physics. When pressed, they can transform one into another or cascade into one or more of the traditional grounds of review developed at common law”. [Robert French “The Rule of Law as a Many Coloured Dream Coat” (Singapore Academy of Law 20th Annual Lecture, Singapore, 18 September 2013) at 18.] It has also come in handy when cases before the Court have dealt with scientific concerns, such as D’Arcy v Myriad Genetics Inc, [[2015] HCA 35, (2015) 325 ALR 100] a case about the patentability of DNA. But I wonder whether the real insight to be obtained from what his scientific background has brought to the Chief Justice’s work is to be picked up from his reference to his gratitude that he was exposed to a “culture” of science. That may give some insight into a style of leadership that, to an outside view, seems more collaborative and cooperative, less competitive than is sometime encountered in appellate courts, perhaps because their members are often drawn from a section of the profession with a very different, more competitive culture.” (footnotes from original, inserted in square brackets)

Science is about finding out what happens, theorising about why it happens, and using that to predict what will happen. Observations usually involve measurement and consequently mathematics. From observations theories can be formulated, again they are usually mathematical. The mathematics should suggest what future observations will be. Predicting observations using mathematics is not always accurate, in which case refinements of the theory are needed. Refinements are prompted by unexpected observations.

For example, looking at magnets and wires, inconsistencies between the predictions of classical mechanics and Maxwell's equations about the forces impelling a current in a conductor, depending on whether the conductor or the magnet is moved, prompted Einstein - at least according to the way he wrote his paper - to develop what later came to be known as the special theory of relativity. The paper announcing this was called (in English translation), On the Electrodynamics of Moving Bodies. Measurements of an event made from different frames of reference (here, in the special case of reference frames moving in straight lines at constant velocities) depend on the point of view, and this in turn has implications for measurements within a single frame of reference. Using observations on the constancy of the speed of light in a vacuum, and theorising that the laws of physics are the same everywhere, Einstein borrowed mathematical techniques developed by Lorentz and showed that some refinements - albeit extremely small ones for the events we normally observe - must be made to Newton’s laws of motion. In a later addendum he showed that the same mathematics he had used also predicted how the energy in matter is proportionate to its mass.

While that sort of mathematics has proved to have great predictive value where observations are made at the macroscopic level, it is not so useful at the sub-atomic level. It seems that the smaller something is, the greater the need for a mathematics incorporating probability. At the sub-atomic level, mathematics is a less accurate predictive tool than it is for events at a larger scale. To compensate for the reduced usefulness of basic mathematics at the sub-atomic level, new forms of mathematics are devised, starting with quantum mechanics. Specialists develop new forms of mathematics to meet the needs of inquiry; Descartes combined algebra and geometry, Newton and Leibniz independently developed calculus (these are all from the Western point of view, in the East these things occurred much earlier), and today there are many forms of specialised mathematics, taking their topics far beyond a lay-person’s understanding.

Unless a mathematical refinement has predictive value for those who must use it, it is worthless to science. The same need for predictive value applies to theories that are not mathematical.But having predictive value is not the same as identifying what is real. The correct interpretation of reality using quantum mechanics has yet to be achieved. A theory may predict observations while not necessarily saying what is real.

Law is like science in that in considering a legal problem a lawyer will try to predict what a court would decide the answer should be. The facts of the legal problem are like measurements in science. But they also claim to speak of reality. Deciding what should be the legal consequence of the forensically decided reality can be like using a scientific theory to predict the result of an experiment. Where a judge has a discretion, or where judgment must be exercised by a court, there is room for a predictive theory to be developed. Those areas of law, where there are discretions to be exercised and evaluations to be made, are different from other areas where the answer to a legal problem can simply be looked up. Discretion and judicial evaluation invite analysis and development of predictive theory.

Two areas of judicial decision-making that have particularly interested me both involve evaluative judgments: deciding whether improperly obtained evidence should be ruled inadmissible, and deciding whether the evidence in a case is sufficient proof of guilt.

My study of the decision whether a court should rule improperly obtained evidence inadmissible is available at . There is a method behind my theory which has mathematical analogues: the Cartesian plane, a diagrammatic representation of results of cases, a boundary curve reflecting the rationality of the decision process. It provides a pictorial representation of results, and a method for identifying wrong decisions. Wrong decisions are like inaccurate scientific observations; they do not require rejection of an inconsistent theory unless they build up in number and have consistency among themselves to the point where it is no longer useful to call them wrong.

The sufficiency of evidence as proof of guilt is an inherently probabilistic question. Reasoning with conditional probabilities is something we all do instinctively, but mathematical analysis can reveal fallacies in intuitive thinking. Analogies from mathematical theory can indicate the probative value of items of evidence and the effect of those on the probability that a defendant is guilty. Law does not require mathematical precision, but mathematical method can be a useful tool. I illustrate this in my draft paper (draft because I like to have the opportunity to keep these papers up to date) available at .

 Those are illustrations of some of the ways in which a background in science can be of assistance to a lawyer.

Saturday, April 07, 2018

Kalbasi v Western Australia: analysing conviction appeals without Weiss

In Kalbasi v Western Australia [2018] HCA 7 the Court split 4-3 on whether Mr Kalbasi’s conviction was a substantial miscarriage of justice.

In trying to answer this question the judges used a notoriously difficult decision of the Court, Weiss v The Queen (2005) 224 CLR 300;  [2005] HCA 81. The differences in the conclusions reached by the judges suggests that Weiss doesn’t work.

In New Zealand we no longer struggle to decide whether a miscarriage of justice is “substantial”. The reformed law is in s 232 of the Criminal Procedure Act 2011.

True to say, Weiss has some lingering influence here, by way of applying Matenga v R [2009] NZSC 18, as can be seen in Wiley v R [2016] NZCA 28 at [18], [49], [51], but that may be only a clinging-to-the-wreckage instinct which the Supreme Court could well correct when it decides the appeals in Z v R (the leave decision was [2017] NZSC 172, 17 November 2017, not available online.)

How would Kalbasi have been decided under s 232?

Kalbasi is a wonderful example of a plethora of appeal issues arising from relatively straightforward facts. Jeremy Gans discusses these at the HCA blog.

I think that, applying s 232 here, we would agree with the conclusion reached by the majority in Kalbasi.

Was the trial unfair (s 232(4)(b))? At common law a trial is fair if the law was accurately applied to facts that had been determined impartially. Impartially includes without bias and without apparent bias, and requires that the fact-finder has given appropriate weight to the various items of evidence and has reasoned correctly.

Although there was an error of law in Kalbasi – everyone thought the presumption of purpose of supply applied, but it didn’t because the charge was only one of attempting to have possession (of methamphetamine) for the purpose of supply. It was an attempt because the police had substituted salt for the drug in the package. The error was immaterial for two reasons: the defence that was relied on (absence of proof of possession) made the subsequent issue of purpose irrelevant, and the quantity of the drug had been about 2000 times that at which the presumption is triggered, so there would have been, without a presumption, a strong factual inference for the defendant to raise a doubt about if that purpose had been contested.

So as a practical matter, the error of law didn’t matter. In some trials it is necessary for all defences to be considered, even those on which the defendant has not relied, but in this case the facts made a contest on the issue of purpose hopeless for the defendant. The error of law was inconsequential on these facts.

Were the facts determined impartially? The issue on possession was whether the defendant had exercised a power of control over what he thought was the drug. Control was properly explained to the jury. The defence was that the defendant did not have control because he was just present to take a small quantity of the drug for his own use. Usually, this would be a defence offered to negate the allegation of purpose of supply. But in the circumstances here the tactical decision to challenge possession rather than purpose was not unreasonable.

The defendant did not give evidence, and there was no criticism of that choice. It left the issue of possession, and more precisely of control, as a matter of inference. There were circumstances that supported the conclusion that Mr Kalbasi had a greater interest than merely obtaining a small quantity of the drug for his own use.

Given that the trial was fair, was there a real risk that the outcome of the trial had been affected by any error, irregularity or occurrence (s 232(4)(a))?

The judge had used a library book analogy to explain the difference between ownership and possession. The same analogy could have more pertinently illustrated the difference between custody and control. If you are the only visitor in a small library, and the librarian leaves the room briefly, you may be said to have custody of the books, but you would only have control of a book you picked out of the shelves. Control may be temporary and conditional on return, and it may be shared, and the evidence was that Mr Kilbasi had worn a latex glove and assisted with cutting or inspecting what he thought was the drug. So even if the library book analogy had not been used in the most apposite way, the jury would not have been misled about what control is.

There was no real risk that the outcome of the trial had been affected by an error, and the conviction was not a miscarriage of justice.