Straddling the point

By the slimmest of margins the Supreme Court of Canada has just avoided making an awful mistake.

Evidence can be admissible without it having to support only one side of a case. This elementary observation is plainly true. Many items of prosecution evidence may be consistent with both the guilt and the innocence of the accused, and only when the whole of its evidence is adduced may the prosecutor be able to say that this proves guilt beyond reasonable doubt.

It is often possible to express the probative value of an item of evidence as a probability, or a likelihood, of the proposition it is advanced to support. This can also be termed the weight of the evidence.

In Gibson v R [2008] SCC 16 (17 April 2008) the accused was charged with driving with excess alcohol in his system, and the issue was whether evidence that his real alcohol level could have been somewhere in a range extending from below, to above, the statutory limit, was admissible. The statutory scheme provided a presumption that the level was as indicated in a test result, but this was rebuttable by evidence that tended to show that the driver’s level was below the limit.

The sort of evidence the defence wanted to rely on was called “straddle evidence”, because it showed a range of possible levels that straddled the limit.

It should have been obvious that this evidence was no different from any other evidence that has a greater or lesser tendency to support the defence in its aim of raising a reasonable doubt. Plainly, where the evidence only has a slight tendency to support an inference of innocence, and is more a basis for an inference of guilt, it will weigh in favour of guilt. In such a case, it is likely to be insufficiently relevant to a defence proposition to be admissible as defence evidence (while being admissible – if the prosecution had obtained it, which of course here they hadn’t – for the prosecution).

In Gibson the defence expert indicated a range between 40 and 105 (the limit is 80). The majority held that this evidence was admissible: McLachlin CJ, LeBel and Fish JJ jointly, and Binnie and Deschamps JJ jointly. However, although admissible, these Judges differed on whether it was insufficient to raise a reasonable doubt. Binnie and Deschamps JJ held that it was sufficient to do so as the “prevailing direction” of the range was under the limit. But the other three Judges who agreed on the admissibility point held that the range of values and the extent to which the range exceeded the limit indicated that the evidence was insufficient to raise a reasonable doubt.

The awful mistake was made by the minority, Bastarache, Abella, Charron and Rothstein JJ (jointly, delivered by Charron J). They held that instead of being evidence in support of a reasonable doubt, straddle evidence was an attack on the presumption itself, and was therefore inadmissible. On this view, straddle evidence only tended to show that the accused fell into the range of people targeted by the legislation (para 33), and that it did not tend to show that the driver in question was not in this range. In order to raise a reasonable doubt, the driver could only adduce evidence of his actual alcohol consumption.

It is difficult to see why evidence that supports an inference of innocence (to the extend sufficient to raise a reasonable doubt) should be seen as an attack on the rebuttable presumption itself. The reasons are given in para 32 (and see also 19 – 20), and essentially come down to saying that Parliament must have taken into account the possible range of actual alcohol levels in drivers’ systems when it established the limit and the rebuttable presumption, and so the presumption could only be rebutted by evidence other than that based on metabolic rates of alcohol elimination in the population at large.

That, however, is to overlook the point that the evidence concerning the population at large must relate to the facts of the case: to the driver and the amount of his actual consumption (see McLachlin CJ, LeBel and Fish JJ at 58). Otherwise, the expert evidence has no weight. The minority’s mistake was to overlook the fact that it would be impossible for the defence to rebut the presumption by evidence of the driver’s consumption, without also adducing evidence of the level of alcohol that one would expect to find, and that could only be based on evidence from the population a large which would inevitably involve metabolism.

Imagine that the defence called evidence that satisfied the minority’s criterion: that the driver’s level fell within a range that was entirely below the limit. The prosecution might then seek to rebut this by calling evidence that his range straddled the limit. Why should straddling evidence be allowed to prove the driver was over, but not under, the limit? The alternative, that neither side should have recourse to straddling evidence, would be untenable because it would prevent the prosecution contesting the defence evidence.

But that’s not all. None of the judgments refer to the correct way in which the proposed evidence would be given. In accordance with Bayes’ Theorem, the expert should present the findings as a likelihood ratio: the probability of getting the results, given that the defendant was guilty, divided by the probability of getting the results, given that he was not guilty. The findings concerning straddling are only part of the data behind the result that the expert should report to the court. The minority’s restrictive approach would limit expert testimony to occasions where the testing indicated a very low posterior ratio of probability of guilt to probability of innocence, and this would be inconsistent with the presumption of innocence and the requirement that the defence only raise a reasonable doubt.

As an alternative to the rebuttable presumption, Canada may find more attractive the approach adopted in jurisdictions where there is a conclusive presumption. In para 76 LeBel J mentioned the issue of limitation on the presumption of innocence, but it is clear that such limitation would be demonstrably justified in a free and democratic society. That is the test in New Zealand under s 5 of the Bill of Rights, and we have a conclusive presumption in this context: s 77 Land Transport Act 1998; no one has as yet argued that this is unjustified.

And on a completely different matter, dicta in this case (para 50 – 51) illustrate a point that has been of some interest in another context: a requirement that the defence “show” something, in order to rebut a presumption, is not the same as a requirement that the defence “prove” that thing. The defence can “show” the thing (innocence) by raising a reasonable doubt, and this is not the same as “proving” it. See Hansen v R (blogged here 20 February 2007).


The fairness of inequality

Should the defence always be given the same access as the prosecution has to the criminal histories of people on the jury panel?

In R v King and Stevens [2008] NZCA 79 (10 April 2008) it was held that it was lawful for the police to access the criminal records of potential jurors, and that it was lawful for this information to be passed to prosecuting counsel. It was further held that where fair trial concerns warrant it, such information must be disclosed to the defence. One member of the Court, Robertson J, held that the defence should always be given this information, but the majority (William Young P and Chambers J) took a more restrictive approach, giving as examples of where disclosure to the defence would be appropriate (para 125):

“(b) Counsel for an accused serving police officer may wish to exclude any juror who may be thought to have an anti-police attitude. …

“(c) Counsel for a man accused of murdering a burglar and who is running self-defence and provocation may prefer a jury which does not include too many convicted burglars.”

The general requirement as formulated by the majority was (para 129):

“…disclosure will be appropriate (and should be directed by the Judge if necessary) where a defendant can point to some likelihood that, in the context of the particular case, jurors with criminal histories may have an adverse predisposition towards the defendant or the defence which is to be advanced.”

It is possible that prosecutors will be inclined to cite the specific instances mentioned in para 125 as if they were the only sorts of circumstances in which this general requirement applies, namely where the potential juror may be biased against the accused.

How, then, did the majority on this point justify inequality in automatic access to this information? After all, the Solicitor-General had, in argument, conceded that the defence should have the information automatically. The majority found this concession was over broad (para 123). They noted the difference between jury-vetting, which they saw as the exclusion of unfavourable jurors, and jury packing, the getting of a favourable jury. The crucial reasoning is at para 127:

“A requirement that criminal history information about potential jurors be automatically made available to the defence would equate the Crown purpose of seeking a jury which is free of those with non-disqualifying but perhaps still serious criminal histories with a defence desire (impractical of achievement though it may be) that a jury include people with such convictions. As far as we are aware, and leaving aside some obiter dicta in R v Sheffield Crown Court, Ex parte Brownlow [1980] QB 530 (CA), no Court has been prepared to proceed on that basis. Instead, courts in New Zealand (see Greening [1991] 1 NZLR 110 (Tipping J, HC), Watson CA384/99 8 May 2000 and Tukuafu [2003] 1 NZLR 659 (CA)), England and Wales (see Mason [1981] QB 881 (CA) and McCann (1990) 92 Cr App R 239 (CA)) and Australia (see Katsuno (1999) 199 CLR 40) have rejected the contention that there is anything inherently unfair in a defendant being tried by a jury where the Crown prosecutor has had access to previous conviction histories for the purpose of exercising rights of peremptory challenge (or the functionally equivalent right to direct potential jurors to stand by).”

This comes down to saying that it is OK for the Crown to want a jury that is not biased against it, but in practice it has not been thought OK for the defence to want a jury biased in its favour. Jury-vetting is acceptable, but jury stacking is not.

That may well be good policy, and the majority held that any change should be left to Parliament. They emphasised an important point made by Robertson J (para 119, referring to para 31): examination of the relevant legislative history shows that Parliament expressly rejected a ban on jury-vetting by the prosecution. This does not quite justify the majority position, however, because it is not to say that Parliament rejected defence access to the same information as was obtained by the prosecution from the criminal history database. Indeed, as all Judges noted (Robertson J at 89, William Young P and Chambers J at 116) the New Zealand Law Commission (Juries in Criminal Trials) has recommended that the defence should have automatic access to such information.

Should either side be allowed to vet, let alone try to stack? Peremptory challenges are not allowed in England and Wales (as both judgments note), but should they be abolished? While they are allowed, it seems wrong to impose traditional restraints on access to information when responsible defence counsel would, these days, run the prospective jurors’ names through Google (a point alluded to in para 98 of the joint judgment). Official coyness about disclosure of well deserved convictions seems quaint, especially as they must be disclosed in many situations where a person seeks a responsible position. Given that peremptory challenges are allowed, equal access to information about prospective jurors should ultimately be adopted.