Posner gives us some holiday reading

It is impossible to have more fun than to spend a little time in the holidays reading Richard A Posner, Divergent Paths: The Academy and the Judiciary (Harvard University Press, Cambridge Mass., and London, 2016). Here is a snippet (p 13):

“Law schools will do almost anything to boost their ranking in U.S. News & World Report, which treats faculty-student ratio and number of library books as plus factors in the ranking, though they have little (library books virtually nothing) to do with the quality of legal education.”

And on the topic of judicial embrace of multifactor tests as aids to judicial decision making, which Judge Posner calls a common pretense of analytical rigour in adjudication, (p 117):

“Not only is the list of factors usually open-ended and therefore incomplete, but the factors are rarely given weights, and so unless all line up on one side of the dispute no decision can be derived from them; they are window dressing.”

And as a federal appellate judge, Posner has this to say about judicial disagreements (p 235):

“The problem of feuding federal judges would be solved in a trice if the Chief Justice summoned them to his office in Washington and told them to stop behaving like children.”

Well, I’m not trying to summarise what Posner says in this endlessly interesting book. We who are not Americans can easily see its relevance to our own legal environment.

Posner, who, to put it mildly, is one of the more intelligent judges, embraces Bayesian reasoning with conditional probabilities. A small glitch – surprising and ironic – occurs on pp 338-339 (if my Kindle’s pagination is correct) in his illustration of why lawyers need to be able to understand DNA evidence. But never mind.

I have, over the years of writing this blog, referred to Posner on several occasions. His fearless brilliance is an inspiration for jurists, and his enthusiasm brings both joy and outrage. And laughter.


Provoking thought – a new issue of NZCLR

You can, on reading a new issue of a law journal, be provoked into thought. Not always, but the latest New Zealand Criminal Law Review, [2017] NZCLR 152-313 (freely available at the New Zealand Criminal Bar Association website) is a positive example.

I have found myself wondering about the following things:

Ink molecules stuck in paper fibres, bits and bytes: is the medium the message?

Is an electronic file a document? Why shouldn’t it be? Should the word “document” in a statute be construed electronically or functionally? In Dixon v R [2015] NZSC 147 the Supreme Court took a functional approach. It seems significant to me that the Court applied s 6 of the Interpretation Act 1999, which simply provides: “An enactment applies to circumstances as they arise.” This is the “always speaking” quality of enactments, discussed from an Australian perspective in a case note on Aubrey v The Queen [2017] HCA 18, by Dan Meagher. It matters not that at the time legislation came into force there were no electronic documents, because the question is whether in the relevant statutory context and in the light of its purpose, the word “document” should include an electronic file. This is the functional approach. Whether an electronic file actually exists in a determinable location is irrelevant to a functional approach. If the file can be read, saved, shared, and in some cases edited or annotated, it functions as a document.

The habit that lawyers have of finding difficulties where there are none can impede the social utility of legislation. In seeking to give effect to legislative intent the courts will try to keep the law as simple as possible. There is a risk that scholarship in a new area of law will, in anticipating judicial decisions, needlessly divert attention to irrelevancies. I am not saying that it has here, just that it might have.

We can’t be wrong about ourselves (can we?)

Another thing I have been provoked into wondering about is the inherent jurisdiction of courts. If the highest court in a hierarchy rules that inherent jurisdiction on a particular point exists, then that must necessarily be correct, unless the court failed to notice legislation that expressly excluded such jurisdiction. Where the highest court considers relevant legislation and interprets it as being consistent with the existence of an independent inherent jurisdiction, then that is the law. What point is there in arguing that the court was wrong?

This arose in discussion of Marwood v Commissioner of Police [2016] NZSC 139. There, the Supreme Court held that in a civil action for forfeiture of criminal proceeds a court has an inherent jurisdiction to exclude improperly obtained evidence. Prior to that it had been conventionally thought that in a civil case there is no jurisdiction to exclude improperly obtained evidence except in extreme cases. Central to the issue was the implications of s 30 of the Evidence Act 2006, which provides for when improperly obtained evidence may be excluded in criminal cases. The critical words are “This section applies to a criminal proceeding”. Does that mean there is no exclusion in civil cases, or is s 30 just setting out the method for the decision in criminal proceedings and being silent as to civil proceedings? The Supreme Court effectively answered those questions in Marwood.

Arguments about whether there should continue to be the inherent jurisdiction recognised in Marwood should now be addressed to the legislature, not to the courts. They will be policy arguments, not fine-grained arguments about statutory interpretation. And they would probably end up by concluding that a total prohibition on exclusion of improperly obtained evidence in this sort of civil case would be wrong, but that a statutory framework for the decision process, analogous to s 30, might be appropriate. It may not be, because the inherent jurisdiction gives the courts flexibility to develop a process appropriate to the needs of cases as they arise.

Are good people better than ordinary people?

This issue of the journal includes a clear and comprehensive summary of an important case on when recklessness is a component of mens rea. There are suppression orders still in place, so I don’t give the citation. But I would be more confident than the author of the case note seems to be that the decision applies generally, wherever an offence is not of absolute or strict liability but where liability is not expressly limited to intent or belief. I would also wonder why the court needed to say that a person is not reckless if they are honestly doing their best to comply with the law. Just unreasonably taking a known risk is the conventional way of describing recklessness. Has the threshold for recklessness been raised by requiring people to do “their best” to comply with the law? Why is compliance with the law mentioned at all, when the traditional definition of recklessness simply asks whether the defendant’s action in taking the known risk was reasonable? Don’t ask. Is “doing one’s best” to comply with the law compatible with the taking of any risk of breaking the law? There is potential for jury confusion and requests for further explanations of the relationship between what it was reasonable for the defendant to have done and what a reasonable person doing their best to comply with the law would have done.

A good book about bad things

The journal includes book reviews, and I was pleased to favourably review Robert J Frater QC’s Prosecutorial Misconduct (2nd ed, Thomson Reuters, Toronto, 2017). Editing has its perils: why did the editors changed my correct reference in footnote 19 to the ONSC to make it an incorrect reference to the ONCJ?

Are obvious opinions irrelevant or just unhelpful?

A witness who gives the court an opinion may have no better information than that already available to the court, and may be in no better position to come to an opinion than the fact-finder.

In such a case the admissibility of the witness’s opinion is (in New Zealand) governed by ss 23 – 25 of the Evidence Act 2006. Evidence of an opinion is not admissible in a criminal case except pursuant to ss 24 and 25.

Section 24 provides:

A witness may state an opinion in evidence in a proceeding if that opinion is necessary to enable the witness to communicate, or the fact-finder to understand, what the witness saw, heard, or otherwise perceived.

Where the fact-finder is in just as good a position as the witness to form an opinion, the s 24 requirement of necessity is not met. Section 24 does not, in such a case, allow the opinion to be given in evidence.

Sometimes a witness will have specialised knowledge, not available to the fact-finder, on which an opinion is based. Then the admissibility of the opinion will be governed by s 25. Subsection (1) provides:

An opinion by an expert that is part of expert evidence offered in a proceeding is admissible if the fact-finder is likely to obtain substantial help from the opinion in understanding other evidence in the proceeding or in ascertaining any fact that is of consequence to the determination of the proceeding.

The definitions of opinion, expert, and expert opinion in s 4 are explanatory and consistent with ordinary usage.

Merely satisfying the criteria in ss 23 or 24 does not render opinion evidence necessarily admissible, as it may be excluded by another provision of the Act, such as s 8 (prejudicial effect exceeding probative value).

In a recent decision, currently suppressed ([2017] NZCA 430), our Court of Appeal has held that another section that may apply to exclude opinion evidence that does not go further than the fact-finder can go without the witness’s opinion, is s 7. This is headed “Fundamental principle that all relevant evidence admissible”, and reads:

(1) All relevant evidence is admissible in a proceeding except evidence that is—

(a) inadmissible under this Act or any other Act; or

(b) excluded under this Act or any other Act.

(2) Evidence that is not relevant is not admissible in a proceeding.

(3) Evidence is relevant in a proceeding if it has a tendency to prove or disprove anything that is of consequence to the determination of the proceeding.

In effect, the Court of Appeal has read words into subsection (3), as if it read (adding the blue words):

(3) Evidence is relevant in a proceeding if it has a tendency to prove or disprove anything and is capable of assisting the fact-finder in determining anything that is of consequence to the determination of the proceeding.

The Court drew that from dicta requiring evidence to  be reasonably capable of supporting the fact in issue: Bain v R [2009] NZSC 16 at [40].

I do not think that it was necessary for the Court of Appeal to read words into s 7. An opinion, as defined, on a fact in issue will necessarily be relevant, unless it is equally consistent with proof, as with disproof, of the fact in issue. It will have a tendency to prove or disprove something of consequence to the determination of the proceeding, just as the fact-finder’s opinion will. The point is that, in the case that has given rise to this discussion, the witness’s opinion had no more probative value than the opinion that the fact-finder could come to independently. It was relevant, but inadmissible because it did not satisfy the requirements of ss 24 or 25: it was not “necessary” and it was not likely to give the fact-finder “substantial help”.

Beyond reasonable doubt

We may agree on what something is, even if we disagree on how it should be described. We may both be looking at a circle; you may describe it as having a circumference of a particular length, while I may describe it as having a radius of a particular length.

Do we have to agree on how to describe what “reasonable doubt” means? Does it have a utilitarian or a pragmatic function; is it a quality like “good” (remembering GE Moore’s difficulty in defining “good”). Does it have a function at all, or is it just a feeling?

Is it describable in terms of knowledge? To ask “what do I know” is to summon the ideas of knowledge and belief. What are the conditions that I require to be satisfied before I am prepared to say I believe something? Do I rely on experience, feeling, logic, or persuasive rhetoric? Do I have to use the same criteria for belief as you use?

Often juries will ask judges for a definition of “beyond reasonable doubt”. While courts may differ in their responses, do their differences conceal an agreement?

I have previously discussed the leading New Zealand case on this: R v Wanhalla [2006] NZCA 229; [2007] 2 NZLR 573. Now the High Court of Australia has considered the same issue: The Queen v Dookheea [2017] HCA 36 (13 September 2017).

The HCA prefers that explanations of what proof beyond reasonable doubt means should not be attempted, and in particular a contrast with proof beyond any doubt should be avoided. It is, however, acceptable and even useful to contrast the high criminal standard of proof beyond reasonable doubt with the lower civil standard of proof on the balance of probabilities. “[A] reasonable doubt is a doubt which the jury as a reasonable jury considers to be reasonable (albeit, of course, that different jurors might have different reasons for their own reasonable doubt)” (at [34]), and ([35]):

“… it is the votes of each of the individual members of the jury that are determinative of the verdict of the jury as a whole. Each juror is appointed to consider the evidence and to decide whether it satisfies him or her of guilt beyond reasonable doubt; and, in order to discharge that function, each individual member of the jury must in effect enquire of himself or herself whether he or she entertains a reasonable doubt. In practical reality, each individual juror may at some point in the course of the juror’s consideration of an issue have a doubt which, upon reflection and evaluation, he or she is disposed to discard as an unreasonable doubt.”

Clumsily put, if one objects to unnecessary gender pronouns, but there you are.

In New Zealand, explanations of beyond reasonable doubt may be attempted: acceptable is, “an honest and reasonable uncertainty left in your mind about the guilt of the accused after you have given careful and impartial consideration to all of the evidence.” But this is not mandatory, and it “is sufficient to make it clear that the concept [of proof beyond reasonable doubt] involves a high standard of proof which is discharged only if the jury is sure or feels sure of guilt.” Focusing on doubt may be misleading, because a doubt need not be articulable and what is required is proof to the required standard. It is acceptable to tell a jury that proof to a certainty is not required. But it is wrong to tell a jury that they need to be as sure of guilt as they would be about an important decision in their own lives.

Don’t ask for more: lawyers are not philosophers. The law does, however, cherry-pick the philosophies it wants.

Utilitarianism asks, what is in the best interests of society? Individual interests are subordinate to society’s interests, individual rights are minimised, and as far as crime is concerned, a deterrent policy is pursued to protect the peace of the community. On the topic of the criminal standard of proof, a utilitarian would acknowledge that it must be higher than the civil standard, but not all that much higher.

A pragmatist would ask, what works? The ends justify the means. Pragmatism may strive for a workable balance between utilitarianism and morality. While absolute proof of a criminal charge is not required, pragmatism justifies a high, but not too high, standard of proof.

A moral view (and here I  acknowledge that these are all moral theories, but I just say “moral” here to avoid having to say deontological) is that it is better to let (insert your preferred value) guilty people go free than to convict one innocent person. It reflects a judgement about what is right or good in the context of a criminal trial, and it favours a very high standard of proof.

These themes are found in the various approaches to instructions on the standard of proof. To say that the standard is higher than the civil standard is to make a utilitarian point. It doesn’t get very far by way of explanation, but it is a start. To add that the fact-finder must “be sure” on a “reasonable” assessment of the evidence, is a pragmatic theme, taking the explanation beyond the utilitarian but not pushing it as far as morality would claim it should be taken. Also pragmatic is the illustration of taking the care one would take over an important decision in one’s own life. To say that proof to a mathematical certainty is not required but the standard is nevertheless very high, is to emphasise the moral theme.

Another area of the law in which these three themes are illustrated is the part of the law of evidence which concerns the decision whether to exclude improperly obtained evidence. A balancing model is widely used for this (and in New Zealand is enacted in s 30 of the Evidence Act 2006). Factors favouring admission of improperly obtained evidence are utilitarian: society is best served if people charged with offences have trials on all the available evidence. Exclusion factors are moral, reflecting the idea that those who enforce the law should obey the law. The balance between these factors is struck pragmatically: what is required for an effective and credible system of justice?

You can’t really be surprised when a jury wants assistance with the concept of proof beyond reasonable doubt. Nor at the reluctance of judges to get into the extent to which deontological ethics may be modified by pragmatism. It should be reassuring, however, to remember that philosophy is just simple ideas dressed up in hard words, in contrast to law which is hard ideas dressed up in simple words.

Ruminate on this!

No doubt you enjoy puzzles:

There is a group of animals, one third of which are sheep. One animal was examined and found to have four legs. The scientist who did that examination tells us that the result “four legs” was three times more likely if the examined animal was a sheep than if it was not a sheep. What is the probability that the examined animal was a sheep?

Most trial lawyers should be able to correctly answer that almost instantly. I have posted the answer in my comment on my alternative site.

Legitimate presuppositions about guilt and innocence

Before the evidence involving the defendant’s acts in a case is considered an assumption may be made about the likelihood that the defendant is guilty. This is different from the presumption of innocence, which simply means that the prosecutor must prove that the defendant is guilty and that the defendant does not have to prove innocence (see R v Wanhalla 24/8/06, CA321/05, [2007] 2 NZLR 573, (2006) 22 CRNZ 843 at [49], mentioned here on 25 August 2006). But – at least on a mathematical approach to conditional probabilities – there must be some starting assumption about whether the defendant is guilty in order that the effect of evidence can be determined. The ultimate decision, the verdict, will depend on how the evidence has affected the prior likelihood of guilt.

The “priors” can be expressed as a likelihood of guilt compared to a likelihood of innocence, each assessed before the evidence as to what the defendant did is considered. A ratio of probabilities is the same way of expressing this comparison of likelihoods. Are there appropriate numbers for making this comparison?

For some people – in the absence of evidence on the point given at trial – a starting point may be that a probability of guilt of 0.02 (that is, two chances out of a hundred), and a corresponding probability of innocence of 0.98, are a good way of reflecting the need to be fair. Almost certainly innocent, but recognising that there could be room for error about that, seems like a fair starting point. This might be the same likelihood ratio as for anyone chosen at random. Indeed, a criterion of random selection can lead to very small probabilities of guilt, for example if the population of a large city is taken as the reference group.

Other people might say, well, the defendant is either guilty or not guilty, so an equal chance of each alternative is a neutral starting point. For these people a probability of guilt of 0.5, and the same probability of innocence, is a fair starting point. Refusing to start with an inclination either way seems fair.

Currently, it is not routine for this to be mentioned in a trial. This may be because it is by no means clear that a starting point is necessary: why not just listen to the evidence and get on with it? The reason is that logical errors are likely to occur. A fact-finder will naturally ask, how much more consistent with guilt than with innocence is this evidence? This is the same as asking, what is the probability of the evidence existing on the assumption that the defendant is guilty, compared with the probability of that evidence existing on the assumption that the defendant is innocent. Having estimated that ratio, it would be tempting, but wrong, to conclude that the ratio expressed the defendant’s probability of guilt compared to probability of innocence. For example, if the issue to be determined was whether an unseen animal was a sheep, and the evidence was that it had four legs, the probability of getting the evidence that it had four legs if it was a sheep (P = 1) is not the same as the probability that it was a sheep if all that is known is that it was a four-legged animal. The error is called transposing the conditional.

Another reason for the priors not being mentioned at trial may be that there is no need to do so. Some evidence setting the scene, background evidence, is likely to have been given as part of the narrative. For example, if a crime was committed by a person in a building, video surveillance evidence may be that only 10 people were in the building around the relevant time, including the defendant. This supports priors of P'(G) / P'(NG) = 0.1 / 0.9. Another example is where it is conceded by the prosecutor that only one of two people could have committed the crime, the defendant being one. It would be intuitive to think that this gave equal priors of P(G) = P(NG) = 0.5. But the prior likelihood of each suspect being the offender may not be equal, and the question becomes to what extent should the fact-finder be given evidence of the unevenness of the respective prior likelihoods.

To get from the evidential likelihood ratio P(E|G) / P(E|NG) [which is read as: the probability of getting the evidence, given that the defendant is guilty, compared with the probability of getting the evidence, given that the defendant is innocent] to the ultimate issue ratio of P(G|E) / P(NG|E) – that is, to legitimately achieve the transposition – it is necessary to multiply the likelihood ratio for the relevant issue by the priors. The need to do this comes from mathematical logic, in a rule known as Bayes’ Rule or Bayes’ Theorem. A form of the rule useful for lawyers is the “odds form of Bayes’ Rule” described, for example, in Bernard Robertson, GA Vignaux and Charles EH Berger, Interpreting Evidence – Evaluating Forensic Science in the Courtroom (2nd ed, John Wiley and Sons Ltd, Chichester, 2016) at 189, [A.2.7]. The logic applies to all forms of conditional probability evidence, not just to scientific evidence. And anything, the probability of occurrence of which varies according to context, can be expressed in terms of conditional probability.

This ratio of priors is the starting point mentioned above, and the problem is, how should it be assessed? The risk is that individual jurors might choose different starting points and indeed may choose any position between the alternatives mentioned above. This is why sufficient evidence needs to be given to establish the prior probabilities.

People who think that the priors should be P’(G) = P’(NG) = 0.5 have the advantage of being able, without error of logic, to say that P(E|G) = P(G|E) and that P(E|NG) = P(NG|E). This is because, for them, the priors do not affect the calculation. Using Bayes’ formula reveals that to find the defendant guilty, a person who starts by understanding the priors to mean P’(G) = P’(NG) = 0.5 will only need the combined (that is, multiplied) likelihood ratios of the other evidence in the case to be about 50 to 1: meaning that the combined evidence is 50 times more likely to have been obtained if the defendant is guilty than if the defendant is innocent.

But a person who understands the priors to mean P’(G) = 0.02 and P’(NG) = 0.98, will, to find the defendant guilty, require the evidence to be about 2400 times more likely to have been obtained if the defendant is guilty than if the defendant is innocent. Leaving the assessment of the priors to individual jurors has obvious dangers.

In a civil case, for example an action for compensation for wrongful conviction, the ultimate issue must be proved to a probability of at least just over 0.5. Again, the level of proof required of the evidence depends on the priors. In civil cases it is especially tempting to think that priors of 0.5 each way is fair. To succeed in a claim for compensation the former defendant (now, plaintiff) would have to prove that the evidence in the criminal trial was slightly more likely to have been obtained if the defendant had been innocent than it was to have been obtained if the defendant had been guilty. But it still may be objected that the prior assumption of a probability of guilt of 0.5 is too high and that the probability attaching to a randomly chosen person should be used.

So a person who has been found not guilty, even on the assumption that the priors are 0.5 each way, may nevertheless fail to obtain compensation: this is because, although the evidence was less that 50 times more likely to have been found if the defendant was guilty than it was to have been found if the defendant was innocent, it may have still been more likely to have been found if the defendant was guilty than if the defendant was innocent.

The point is that to make presuppositions about the defendant’s guilt or innocence legitimate, those probabilities must be assessed from evidence given at trial.

It is appropriate to ask whether assessment of evidence outside a trial context should attract the same logic. For example, does the logic apply to assessing the sufficiency of evidence to meet a requirement of reasonable grounds to suspect that evidence will be found in a search? As may be illustrated by the case I discussed here on 31 July 2017, some judges might think it does, some that it doesn’t. Judicial explanations do not go far enough for us to be sure.

I should add that when mentioning “guilt” in the above discussion I am referring to single-issue cases (for example, who did it, or was it done intentionally?). Where several issues are at play in a case, guilt on each will need to be considered separately. That will avoid the swamping effect of a large likelihood of evidence being obtained on one issue (for example DNA evidence proving the defendant’s presence) overwhelming proof of another issue (such as the defendant’s state of mind).

Assessing reasonable grounds to suspect

Whether there were “reasonable grounds to suspect” the commission of an offence can be controversial. Recently our Court of Appeal has divided over whether there were reasonable grounds to suspect that the defendant had possession of an offensive weapon. The case is not yet publicly available, but suppression orders have lapsed. For people who have access to the databases the neutral citation is [2017] NZCA 108. When it is available it should be obtainable at nzlii.org (as number 108 in the list).

Reasonable grounds to suspect that a weapon will be found are required by s 27 of the Search and Surveillance Act 2012. Relevant matters were that it was 3 am when the defendant was questioned on a street and his response was “very cagey” as to where he had come from and why he was in the street and not wearing shoes although it was cold, his clothing (shorts and a camouflage jacket) was similar to that of a person who was believed to be involved in stealing from cars, he kept his hand in his jacket pocket and was behaving in an agitated manner (at [17]). These circumstances where held to have given the officer reasonable grounds to suspect that the defendant was in possession of an offensive weapon. Peters J (who delivered the Court’s judgment) recorded her dissent on this point. She did not consider that the circumstances relating to the initial dispatch to the scene suggested violence or a person with a weapon, and although the defendant was agitated nervousness is insufficient, and the defendant had simply kept his hand in his pocket. Further, he had identified himself, and there was nothing to suggest that he was going to use violence, particularly as four constables were present at the time of the search (at [26]).

The difference between the judges may be due to what assumption was be made at the beginning of the analysis. Should the defendant be assumed to have the probability of carrying a weapon that a randomly chosen person would have, or a randomly chosen person of the defendant’s age, and gender (to mention the two morally acceptable groupings), at that time of night? To avoid exaggerating individual facts which will be considered later in the analysis, the most neutral starting point should be chosen: the probability that a randomly chosen person has possession of a weapon.

However, another starting point sounds as if it is fair, but it will often lead to the opposite conclusion. This is that the defendant is just as likely to have a weapon as not to have a weapon. The even balancing here sounds neutral, until one asks, why should the defendant be assumed to have a probability of 0.5 of having a weapon? It may be that only 2 people out of every 100 have possession of weapons, so why not start with a probability for this defendant of 0.02?

Having chosen a starting point, the particular circumstances are examined. The judges may well have agreed on the probative value of each item and on the effect of taking them all into account together. Suppose that they agreed that the occurrence of these combined circumstances was 14 times more likely if the defendant had possession of an offensive weapon than if he did not. A judge who started with an assumption that the defendant was no more likely to have a weapon than would a randomly chosen person, would conclude that the ultimate probability that he had a weapon was around 0.3. This could not be reasonable grounds to suspect. But a judge who started with the assumption that the defendant was just as likely to have a weapon as not to have one, would conclude that the ultimate probability that he had one was over 0.9. This would certainly be equivalent to reasonable grounds to suspect possession of a weapon.

This analysis, which uses Bayes’ Theorem (something I didn’t mention so as not to put off many readers), shows how important the initial assumption is. A judge who started with the 0.5/0.5 assumption (giving Bayesian priors of 1) would think that was a fair starting point, but was it?

The judgment does not mention whether any offensive weapon was found in the defendant’s possession; other specified incriminating things were found, in respect of which he was charged.