A failed attempt at retrospective criminalisation

Where an "offence is committed by an omission to perform an act that by law there is a duty to perform" (s 4.3(b) of the Criminal Code (Cth), in the form it was at the time relevant to Director of Public Prosecutions (Cth) v Keating [2013] HCA 20 (8 May 2013)), the duty must exist at the time of the commission of an alleged offence. So much is clear from the use of the present tense, as the High Court of Australia unanimously held in Keating at [49].

The offences alleged in Keating, essentially failure to inform the Social Security department of changes in circumstances that may have been relevant to entitlement to receipt of benefit payments, were against s 135.2(1) of the Code. The requirement there, of engaging in prohibited conduct, was that there must be a duty not to omit to disclose the relevant information. A duty of disclosure was introduced (as a result of DPP (Cth) v Poniatowska, noted here on 27 October 2011) by legislation having retrospective effect, but the existence of retrospective effect did not of itself mean that it engaged with the provisions creating the relevant offence: Keating at [47].

"[48] It is not to the point to observe that ignorance of the law affords no excuse or that the prosecution is not required to prove an intention to breach a legal duty. The submission ignores that the failure to do a thing is not an offence in the absence of a legal duty to do the thing [footnote 35: "Code, s 4.3(b)"]]. As explained in Poniatowska, s 4.3 of the Code is a reflection of an idea that is fundamental to criminal responsibility: that the criminal law should be certain and its reach ascertainable by those who are subject to it [footnote 36: "[Poniatowska] [2011] HCA 43; (2011) 244 CLR 408 at 424 [44] per French CJ, Gummow, Kiefel and Bell JJ; and see Glanville Williams, Criminal Law: The General Part, 2nd ed (1961) at 579-580; Ashworth, "Public Duties and Criminal Omissions: Some Unresolved Questions", [2011] Journal of Commonwealth Criminal Law 1"]. This idea underpins the strength of the presumption against retrospectivity in the interpretation of statutes that impose criminal liability. Mr Bennion explains the principle in this way [footnote 37; "Bennion on Statutory Interpretation, 5th ed (2008) at 807 (footnotes omitted)"]:

"A person cannot rely on ignorance of the law and is required to obey the law. It follows that he or she should be able to trust the law and that it should be predictable. A law that is altered retrospectively cannot be predicted. If the alteration is substantive it is therefore likely to be unjust. It is presumed that Parliament does not intend to act unjustly."

So in Keating the new legislation, aimed at overcoming the difficulty identified in Poniatowska, was inadequately drafted to overcome the presumption against unjust legislative intent. It did not render s 4.3(b) of the Code nugatory. It did not make a person criminally liable for past failure to perform what was not then an obligation.

Judicial redefinition of veracity evidence

In our Evidence Act 2006, the veracity rules concern particular kinds of character evidence. They may be used by a defendant to show a propensity to tell the truth, or by a prosecutor to show a propensity to tell lies. Either way, evidence of veracity is only admissible in limited, specified, circumstances.

Confronting a witness with a prior inconsistent statement is not of itself a challenge to the witness's veracity, because veracity refers to a general tendency, not to a particular instance.

Evidence that is admissible independently of the veracity rules is not therefore subject to the constraints of those rules. The veracity rules can permit the adducing of evidence that would not otherwise be admissible.

There are limits on the use of leading questions in examination and in re-examination of a witness. In re-examination a witness may be asked to clarify an ambiguity or an apparent contradiction in evidence given in cross-examination. The witness might also, in re-examination, be presented with a prior inconsistent statement – inconsistent with what the witness said in cross-examination - and asked to explain the inconsistency. This is not, of itself, necessarily cross-examination, although whether it is, and therefore whether it is only permissible if the witness is hostile, is a matter to be determined as an exercise of judgment in the particular case.

A defendant who uses a complainant's prior inconsistent statement is not using it as evidence of a lie, but rather as evidence of the truth (R v Davidson [2008] NZCA 410). But even if the prior inconsistent statement was being used as evidence of a lie, it would not for that reason alone be evidence of (lack of) veracity: it is particular, not evidence of a general disposition. The prior inconsistent statement is admissible as soon as the inconsistency emerges, and the veracity rules are irrelevant.

And obviously, a defendant is not shielded, by the limits on the use of evidence of veracity, from his own prior inconsistent statements (R v Tepu [2008] NZCA 460, [2009] 3 NZLR 216). The veracity rules are again irrelevant, the prior inconsistent statements being particular in nature, not evidence of a general propensity to lie.

These points are made in Hannigan v R [2013] NZSC 41 (26 April 2013). They certainly seem obvious, although the Court split 4-1. The Chief Justice dissented on the grounds that the rule prohibiting cross-examination by a party of its own witness (s 94) should have been applied. This conclusion follows from a different judicial assessment of the quality of the questioning than was made by the majority.

The case was decided on that difference, but the obiter nature of the judicial observations on the veracity rules should not detract from their authoritative status. They give guidance that is obviously of assistance, and (I sarcastically add) at the current rate at which the Court refuses leave to appeal – because counsel don't identify appropriate grounds – we would otherwise have to wait hundreds of years for another opportunity for the Court to clarify the veracity rules.

Anyway, before Hannigan the law on the admissibility of evidence of veracity was uncertain, and the appellant's case was indeed arguable. The dissent illustrates this.

Elias CJ considered the relationship between s 37(4) and s 94. She held that in this case the questions in re-examination were leading and cross-examination [33], [36], and that therefore hostility had to be established. She accordingly disagreed with the majority on the nature of the questions in this case [40]-[41]. She also held that a finding of hostility is always required before a party can cross-examine its own witness, irrespective of whether a prior statement is independently admissible [43]. Significantly, Elias CJ pointed out [46] that the majority approach to the definition of veracity evidence in s 37(5) ignored the particular aspect of the definition: a disposition to refrain from lying, whether generally or "in the proceeding". She took a wide view of when a witness might be held to be hostile [52], and concluded that in this case the judge could, after proper inquiry, have concluded that the witness was hostile [57].

Recently I heard someone say that dissenting judgments tend to become the law in a few decades. No they don't. Dissents very rarely become the law, and it is only because of this rarity that they are noticed when they do, and their tendency to become law is exaggerated. It is not unusual for judges to disagree about the law and about its application to the circumstances of the case they have to decide.

But the effect of Hannigan is to iron out a crinkle in the definition of veracity evidence that occurs in s 37(5). The definition as enacted is too broad insofar as it includes a disposition to lie "in the proceeding". The majority have interpreted s 37(5) by ignoring that inclusion, and have thereby restored the original intention behind the legislation: to restrict evidence of collateral issues. As the majority note at [137], the Law Commission in "The 2013 Review of the Evidence Act 2006" NZLC R 127 (February 2013) has recommended a change to the definition of veracity evidence along similar lines (see 6.56 – 6.69 of the Report). The majority in Hannigan has in effect changed the definition in response to the difficulties that the Law Commission has summarised. [Update: Section 37(5) has been amended from 8 January 2017 by deletion of the reference to "in the proceeding".]

While looking at the Law Commission's report I should say something about its treatment of concerns that have been expressed about s 30 of the Evidence Act 2006. I agree with the Commission's recommendation that the section, which addresses when improperly obtained evidence may be excluded, does not need changing except in a minor way that the courts have anticipated. Decisions under s 30 have troubled academic commentators, who focus on the very few cases that are apparently wrong, rather than on how the section works satisfactorily in the overwhelming majority of cases. I often encounter younger colleagues who, just out of law school, regard s 30 as a "whatever-the-judge-wants-to-do" sort of provision. I hope that attitude does not reflect a failure of teaching. It is much more interesting to work out how judicial decisions under s 30 may be predicted, than to offer unconstructive and uninstructive criticisms.

Search and the implied licence to enter private property

In criminal law the facts can be simple but the law complex. This is why criminal lawyers appear to some observers to be vastly more intelligent than their colleagues who practise in civil law.

The implied licence to enter private property can give rise to differences of judicial opinion on whether a police officer carried out a search and if so whether it was done lawfully.

In Florida v Jardines, USSC No 11-564 the Court split 5-4 on the lawfulness of a search where an officer had taken a drug dog on a lead to the front door of a house intending to knock and speak to the occupier. The officer was acting on information that drug offending was occurring on the property. The dog indicated the smell of drugs and the officer left the property with the dog and obtained a warrant to search the address. When the warrant was executed evidence of cannabis offending was found.

The opinion of the Court, delivered by Scalia J, was that the officer with the dog had carried out a search in breach of the implied licence to enter and knock. The main grounds for this decision were trespass, but in a concurring opinion Kagan J, joined by Ginsburg and Sotomayor JJ, the alternative ground of breach of privacy was advanced as an easier answer. The dissent was delivered by Alito J, joined by Roberts CJ, Kennedy and Breyer JJ.

The facts invite consideration of a variety of issues:

• What was the significance of the presence of the dog?
  
• Do the police have common law powers that ordinary members of the public do not?
  
• Should lawfulness here be determined by considerations of trespass or of privacy?
  

Alito J denied that the implied licence that qualifies trespass had ever been held to have prevented an officer bringing a dog onto the property. Obviously that point is not particularly significant because the law hasn't yet anticipated every possible occurrence. Absence of authority for a proposition is not authority against the proposition, although it can suggest that the conduct has previously been thought reasonable.

Alito J pointed out that the law has never attempted to distinguish categories of visitors as being welcome and therefore within the implied licence or unwelcome and therefore outside the licence. Any visitor with a lawful purpose may enter at a reasonable time of day and walk on the path that typically approaches the front door and, without lingering, knock on the door in an attempt to speak to an occupant. The police may do this too, and they do not search by simply approaching the door to knock and talk, even where the intention is to talk with a view to obtaining evidence against an occupier.

And if, continued Alito J, the officer in approaching the door with that intention, happened to smell evidence of drug offending, that information is not obtained outside the scope of the implied licence. So too for things seen and heard from a lawful vantage point. The officer is permitted to smell, hear and see what any person might detect on a lawful approach to the front door (citing State v Cada, 129 Idaho 224, at 232, 923 P. 2d 469 at 477).

Given that the officer could use his own nose, continued Alito J, what was wrong with him using the dog? There was no authority prohibiting the officer from having the dog with him, and indeed there has been no case in 800 years in which a tracking dog has been held to create a trespass. So, concluded the dissent, trespass is not a proper basis for holding the present conduct unlawful.

Nor, continued Alito J, could the occupiers have any reasonable expectation of privacy in relation to odours emanating from unlawful activities and reaching places where members of the public may lawfully stand. This is not the same as the use of new technology to enhance the sensing of information. It would hamper legitimate law enforcement activity if the dog's nose were to be equated with new technology.

However the dissent must now be regarded as incorrect in the jurisdictions in which Jardines applies. This is not to say that elsewhere the dissent's view of the law should not be accepted. Although the Court was concerned with constitutional interpretation, the origins of the law against unreasonable search and seizure are in the common law of England. While originating in the customs of England, the common law can develop differently according to social needs in different places. And a change in the common law brought about by decisions of the European Court of Human Rights in relation to judicial decisions made in Britain (for example as occurred in Malone v United Kingdom [1984] ECHR 10, overturning Malone v Metropolitan Police Commissioner [1979] Ch 344) does not necessarily affect the common law of another country. So although Jardines is not a "common law" decision in the narrow sense that the term "common law" is used in the United States, it is of interest wherever the meaning of search and the scope of police powers in relation to private property have to be decided.

The opinion of the Court in Jardines therefore is not binding but is "of interest" to courts outside the jurisdiction in which it applies. Scalia J, after deciding that the investigation took place in a constitutionally protected area, turned to consider whether the intrusion was authorised. Inevitably the relevant common law decision, known to the Founders and repeating an ancient custom of the realm, is Entick v Carrington, 2 Wils. K.B. 275, 95 ER 807 (K.B. 1765). As every lawyer knows, or once knew, this case reminds us that "our law holds the property of every man so sacred, that no man can set his foot upon his neighbour's close without his leave."

This rule, underlying the Fourth Amendment, raised the question whether a licence to enter could be implied in the circumstances of this case. Scalia J held that introducing a trained police dog to explore the area around the home was not customarily recognised as being within an implied licence to enter. The scope of the licence to enter and knock on the front door was limited both to a particular area and to a particular purpose. There was no invitation to the officer to enter and conduct a search. It was not the dog that was the problem, so much as the purpose of the entry. The common law would not licence a person who, remaining on the path to the door, used binoculars to peer through a window.

The Fourth Amendment has a property-based interpretation, supplemented in appropriate cases with a privacy based interpretation. Where a case can be decided on property-based grounds there is no need to add an inquiry about whether the defendant had a reasonable expectation of privacy. Here, reasoned Scalia J, the use of the dog and questions about privacy interests in respect of odours emanating from illegal activities on the property, were privacy issues and did not need to be considered because the case turned on property interests. The point was that the officer entered to conduct a search and that was outside the implied licence. Since there had been an unauthorised search, the Court upheld the Supreme Court of Florida's decision that the trial judge had correctly excluded the evidence obtained through entry with the dog and execution of the improperly obtained search warrant.

It is not inevitable that issues concerning searches have to be analysed in terms of first property rights, then if necessary, privacy rights. The reverse can also work, as is illustrated by the concurring opinion in Jardines, and, for an example from further afield, in Hamed v R [2011] NZSC 101, at [163]. Hamed also contains some controversial remarks from the Chief Justice about whether the police have common law powers that ordinary people do not have (she held that they don't), and although the other members of the Court did not directly address that point the Court of Appeal has subsequently decided – although in my view by a bit of a stretch - that Hamed is consistent with the view that the police do have additional common law powers: Lorigan v R [2012] NZCA 264. The consequences of illegality may also differ between jurisdictions, and may be determined by legislation. The interpretation in Hamed of the relevant statute was discussed here on 19 September 2011. Some attempt has been made in New Zealand to codify the law of search: Search and Surveillance Act 2012. In circumstances like those in Jardines the relevant section would be s 20, but this does not specify the bounds of an implied licence. The consequences of a breach of an implied licence are left to be determined in the same way as before the Act (which is due to come fully into force by 1 April 2014, if not earlier by Order in Council). The position is summarised in Adams on Criminal Law – Rights and Powers, para SS20.05:

Where the constable's reasonable suspicion as to the commission of an offence has been derived from the unlawful actions of the police, the exercise of the warrantless search power may be unreasonable in terms of s 21 of the New Zealand Bill of Rights Act 1990: see, for example, R v Hjelmstrom (2003) 20 CRNZ 208 (CA) (consent to presence on property obtained through misleading the occupant). See also Lord v Police (1998) 5 HRNZ 92 (HC). However, even where the police presence at a place is without lawful authority, drugs seized in the course of the exercise of the search power on reasonable grounds may be admissible under s 30 of the Evidence Act 2006: see, for example, Eruera v R [2012] NZCA 288 (cannabis seizure in course of executing invalid search warrant for stolen property). For an example of evidential material discovered in the course of an unlawful search being held to be inadmissible, see R v Yeh [2007] NZCA 580.

This new legislation gives no guidance to the police about what they may do when they enter private property subject to an implied licence.

Your own jurisdiction may well have the same uncertainties as mine. To what extent do common law powers exist in the context of legislation? Do the police have greater common law powers than ordinary members of the public regarding entry onto private property? What are the terms of any implied licence to enter that apply to police officers? Does the characterisation of an entry as a search depend on privacy or on property rights? What sort of detection devices may be used in relation to private property pursuant to the common law?

People unfamiliar with the law's delays might be surprised that these questions can remain after 800 years. Good legal advice would be to set aside a further 800 years for the answers to emerge.

Informed advice on consequences of plea: changing perceptions of fairness

Sometimes when judges make new rules they apply retrospectively to cases that have already been decided. Obviously this could cause chaos, so there are limitations that confine the situations in which this retrospectivity can apply. In the United States, as we saw here on 21 February 2008, the rule in Teague v Lane, 489 U.S. 228 (1989) recognises two exceptions to the general rule that decisions do not apply retrospectively: where laws proscribing conduct have been declared unconstitutional, and where new rules concern the fairness of trials. Teague has been applied recently in Chaidez v United States
USSC No 11-820, 20 February 2013.

In Chaidez the appellant sought application to her case of a rule that had been declared by the Supreme Court after the proceedings in her trial had been finalised. The rule is that counsel must advise a non-citizen client of the immigration status implications of a plea of guilty: Padilla v Kentucky, 559 U.S. 356 (2010). Ms Chaidez had not been advised that her permanent residency would be revoked and that she faced mandatory removal as a result of her guilty pleas and convictions for mail fraud charges that were classified as aggravated felonies.

The Court held that the Padilla rule did not apply retrospectively.

This rather surprising result arose from what the majority regarded as the first issue which was whether advice about deportation came within the Sixth Amendment right to counsel. Does the right to counsel include the right to advice about a collateral matter – the consequences of a conviction on immigration status? Before Padilla the states had almost unanimously held that it does not. Padilla created a new rule for most jurisdictions. This new rule did not apply to Ms Chaidez's case because (the opinion of the Court is not clear on this but one can infer the reason) it did not, in terms of Teague, concern the fairness of the criminal proceedings against her.

Sotomayor J, joined by Ginsburg J, dissented. They reasoned that Padilla did not create a new rule but it merely applied the established rule that legal representation must be to a standard consistent with prevailing professional norms (Strickland v Washington, 466 U.S. 668 (1984)). Those norms had developed to require advice about the immigration implications of a guilty plea. Padilla did not apply a direct-or-collateral consequence approach to the Sixth Amendment, and Ms Chaidez's legal representation had fallen short of the required standard.

Outside the United States a retrospectivity issue of the kind that arose in Chaidez would probably be resolved by asking whether the defendant should have been advised of the consequences of conviction, including deportation. The rules of professional conduct should indicate the extent of a lawyer's obligation to advise a client of the consequences of a decision. For example, the Lawyers and Conveyancers Act (Lawyers: Conduct and Client Care) Rules 2008 [NZ], rule 13.13.1:

"When taking instructions from a client, including instructions on a plea and whether or not to give evidence, a defence lawyer must ensure that his or her client is fully informed on all relevant implications of his or her decision and the defence lawyer must then act in accordance with the client's instructions."

A retrospectivity issue would arise if standards had changed so that although advice on immigration status might not reasonably have been required to have been given at the time the client entered a guilty plea, it would be required now. This is an artificial issue here, as it has long been recognised that such advice must be given. But if there had been a change in this, so that "all relevant implications" now include the effect of a conviction on immigration status, would all defendants who had previously entered guilty pleas without that advice now be able to have their convictions quashed and their pleas re-taken?

While it is true that standards of fairness change over time, defendants who are still around to complain of treatment that by current standards was unfair are likely to have a remedy. See Krishna v The State (Trinidad and Tobago) [2011] UKPC 18, discussed here on 12 July 2011.

Jeopardy from silly acquittals?

"To permit a second trial after an acquittal, however mistaken the acquittal may have been, would present an unacceptably high risk that the Government, with its vastly superior resources, might wear down the defendant so that 'even though innocent he may be found guilty"

This from Green v United States, 355 U.S. 184, 188 (1957) was quoted in Evans v Michigan
USSC No 11-1327, 20 February 2013. Here an acquittal had been directed at trial although on grounds that were plainly wrong. The acquittal was nevertheless valid and effective to invoke the rule against double jeopardy.

Evans highlights the distinction between procedural terminations of trials and findings on the merits. A procedural termination is not an acquittal because it is not a finding on the merits. A procedural termination avoids the defendant being in jeopardy of a conviction. A properly granted mistrial does not give rise to an expectation of finality.

In Evans the judge ruled at the close of the prosecution case that the evidence so far adduced was insufficient to convict the defendant. The judge wrongly thought that the relevant law of arson required proof that a particular building was not a dwelling, and directed a verdict of not guilty accordingly. This was held to have been a ruling on the merits and a bar to a retrial.

You can see that this is a bit silly. We saw an analogous sort of silliness in R v Taylor [2008] NZCA 558, discussed here on 18 December 2008. Taylor was applied in Connolly v R [2010] NZCA 129 at [65]-[66].

It is silly because it turns on the stage of a trial at which an objection is taken: has jeopardy of conviction arisen? If the prosecution case has been closed, then yes, there is jeopardy, as in Evans. But what if, after the jury had been selected and the trial begun, the defence had objected that on the basis of the evidence that the prosecutor intended to call there was no proof of an element of the offence, and before any evidence was called the judge ruled that the prosecutor needed that evidence, and the prosecutor confirmed it would not be adduced, and the judge then directed an acquittal? Would jeopardy have arisen? Is this a procedural termination? The position as it would inevitably be if the prosecution case proceeded to closure is being anticipated. Why wait until closure of the case? Yet the authorities suggest that this would be a procedural termination, not a decision on the merits.

Is there a sensible policy behind treating directions that are obviously wrong in law as nevertheless giving rise to legally effective acquittals? If there is, is it consistent with whatever policy might justify distinguishing between procedural dismissals and rulings on the merits?

Sniffer dog reliability and probable cause for search

There were times when Aldo the drug dog was not on his best form. He was trained to detect the presence of particular drugs, but sometimes he would say one or more of them was there when that was wrong, although on the occasion that concerned the United States Supreme Court there were other drugs present: Florida v Harris, USSC No 11-817, 19 February 2013.

What was the relevance of a record of false positives to the existence of probable cause for a search based on Aldo's indication?

Probable cause requires the kind of "fair probability" on which "reasonable and prudent [people,] not legal technicians, act": Illinois v Gates, 462 U.S. 213. The totality of the circumstances must be looked at, and rigid rules, bright line tests and mechanistic enquiries are inappropriate, according to Gates.

The Court, in a unanimous opinion delivered by Kagan J, considered that field-performance records may not capture a dog's false negatives or may markedly overstate a dog's false positives. This is because in the field – that is, in real-world performance – a dog's failure to detect drugs will often not be followed by a search and so the failure will go unrecorded. Similarly, an apparent false positive may in reality be a correct response to a residual odour or a small amount of drug that the officer failed to find. But evidence of the dog's reliability in a controlled setting, where errors are known, can provide sufficient reason to trust the dog's alert in the field.

All the evidence needs to be evaluated, said the Court. Here the facts supported a finding of probable cause because the defence had not contested the State's evidence that Aldo performed reliably in controlled settings. But where the defence did challenge the evidence of the dog's reliability the court should assess all the evidence and ask whether all the facts, viewed through the lens of common sense, would make a reasonably prudent person think evidence of offending would be found. "A sniff is up to snuff when it meets that test." Haw haw.

Here the problem with the Florida Supreme Court's approach was that:

"No matter how much other proof the State offers of the dog's reliability, the absent field performance records will preclude a finding of probable cause. That is the antithesis of a totality-of-the-circumstances analysis."

There may be other indicia of reliability, and absence of one sort may be compensated for by presence of another.

Because the defendant had not raised issues of Aldo's reliability at trial, he could not do so for the first time on this appeal.

"As the case came to the trial court, Aldo had successfully completed two recent drug-detection courses and maintained his proficiency through weekly training exercises. Viewed alone, that training record—with or without the prior certification—sufficed to establish Aldo's reliability."

Good doggie.

Secondary participation in conspiracy

For a compellingly logical analysis of secondary participation in conspiracy, see R v JF, 2013 SCC 12 (1 March 2013).

Although the form of secondary liability considered in JF is aiding or abetting under s 21 of the Criminal Code, the same reasoning would apply to the other forms of participation that are usually included as constituting secondary participation: inciting, counselling or procuring.

The focus is on the actus reus of conspiracy, which is an agreement to commit an offence. The actus reus for secondary liability is aiding, abetting, inciting, counselling or procuring the formation of the agreement. Because the agreement may continue up to the attainment of its unlawful object, a person may join the agreement after its initial formation. A person who aids, abets, counsels or procures that person to join at that later stage commits the actus reus of secondary participation in the conspiracy.

A person who aids (etc) a conspirator in the attaining of the object of the conspiracy is not for that fact alone a conspirator, because the attaining of the object of the conspiracy is not the actus reus of conspiracy. But that evidence will usually support an inference of assistance in the entering into of the agreement by the person who is aided (etc), and if that inference is permissible in the circumstances then it is evidence of the actus reus of the aider's (etc) secondary participation.

This decision removes doubts that had existed in Canada over whether liability could arise from the mere assistance of a conspirator in the furtherance of the conspiracy. The approach in R v McNamara (No 1) (1981) 56 CCC(2d) 193 (Ontario CA) was not followed.

Old problems with new evidence

Whether failure to call evidence at trial should be grounds for quashing a conviction is an issue that often has to be decided in appeals, as it was in Taylor v The Queen (Jamaica) [2013] UKPC 8 (14 March 2013).

Here the Board split, Lord Kerr dissenting, on the application of the law to the facts. There was no difference of opinion on what the law is.

It was unnecessary to decide whether counsel were at fault in not calling the relevant witness, because the issue is the impact of the absence of the evidence on the verdict: Lord Hope for the majority at [13], applying Lord Carswell in Teeluck v State of Trinidad and Tobago [2005] UKPC 14 at [39], (discussed here on 1 April 2005). The test is whether, after taking all the circumstances of the trial into account, there is a real possibility of a different outcome: Taylor at [20]. Might the evidence reasonably have affected the jury's decision to convict? The majority held that there was no reasonable possibility in this case that the jury would have arrived at a different verdict.

Lord Kerr said that the requirement of a real possibility of a different verdict signifies no more than an acceptance that one is left in doubt as to the safety of the conviction [39]. This, he added (more obscurely), was not a matter for one side or the other to take on the burden of showing, but instead is a matter that must be decided in the round. The question of the effect of the new evidence on the safety of the verdict is for the appellate court to decide for itself; the court does not decide what effect the evidence might have had on the jury: [43], applying Dial v State of Trinidad and Tobago [2005] UKPC 4 (noted here on 17 February 2005). Further, the question is not whether there was evidence on which the jury might reasonably convict, but rather whether there was evidence on which it might reasonably decline to do so: [45], applying Bain v The Queen (New Zealand) [2007] UKPC 33 (discussed here on 11 May 2007).

Therefore it is in this sense, said Lord Kerr, that the question, where new evidence has come to light, is whether the evidence might reasonably have led to an acquittal [46]. He proceeded to analyse the case and reached a different conclusion to that of the majority.

The application of this law is notoriously difficult for appellate courts, and it is not unusual to find dissenting judgments. One also finds dissents in appeals which have to consider, not the failure to call evidence at trial, but the wrongful adducing of evidence at trial. A spectacular example is Howse v R [2005] UKPC 31, discussed here on 23 July 2005. The wrongful adducing of evidence raises the substantive question of the fairness of the trial, and the inevitability of a guilty verdict is not the touchstone, for even a guilty defendant is entitled to a fair trial.

Trial fairness is also raised by a failure to adduce evidence and we might wonder whether the criterion for quashing a conviction in such a case should be whether the absence of the evidence might have undermined the fact-finder's impartiality: could inappropriate weight have been given to critical prosecution evidence because of the absence of the evidence?

Attribution and the actus reus

Sometimes where there is more than one defendant alleged to be a principal offender (that is, one who personally does the actus reus with the required mens rea) it is difficult to say who did what. This is particularly so where there are a lot of eye witnesses, for it is normal to find that everyone has a different account of what happened. There may be no doubt that an actus reus occurred, but who did what?

This was considered in Huynh v The Queen [2013] HCA 6 (13 March 2013). "Joint enterprise" liability of this kind (which is not to be confused with the term joint enterprise in the context of an exception to the rule against hearsay, nor with similar terminology that is sometimes used in relation to extended secondary liability) depends on proof that the defendant was a party to an agreement to commit the offence that was committed and in addition - for this is not mere conspiracy - that the defendant participated in the offending. Presence when the offending occurred can be sufficient to prove participation. The circumstances may also, as they were in this case, be such that the defendant's presence supports an inference that it was pursuant to the required agreement.

This common law solution to the determination of liability as a principal offender where the facts are vague has a parallel in the interpretation of the statutory criterion, for liability as a principal, of being a person "who actually commits the offence": see for example s 66(1)(a) of the Crimes Act 1961 [NZ]. There is an appeal case, the name and details of which seem still to be subject to a suppression of publication order, so I give only the citation for people with access to databases on which publication is permitted: "[2010] NZCA 256". In that case there were several steps needed to complete the actus reus and several defendants were allegedly involved, but no one person did all the steps. In relation to any given defendant, the prosecutor had to prove that that defendant did any of the required steps, that one or more other of the defendants did the other necessary steps, and that the defendant under consideration had mens rea. This was called a distributive application of s 66(1)(a).

Is the distributive approach the same as the joint enterprise liability illustrated by Huynh? Probably yes, although particular facts may produce different results. That would depend on what inference could be drawn from a defendant's presence when another defendant completed a step in the actus reus. The common element is participation in the offending in circumstances where the acts of one defendant are attributed to another.

When will this attribution occur? Policy considerations strongly favour public safety, but there should be clear limits on attribution. For a controversial approach see R v Gnango [2011] UKSC 59, [2012] 1 AC 827, discussed here on 18 December 2011, where the majority favoured liability as a principal for murder where the defendant was in a gunfight with the person who, missing him, shot a bystander.

Guidance was given to judges in both Huynh and "[2010] NZCA 256" on how to handle complex cases, where there are multiple defendants and different forms of alleged liability. Huynh stresses the importance of getting to the real issue in the case, so that the judge can give a focused direction on the law. The New Zealand case at [26] invites judges, when faced with disagreement from counsel on the structure and content of a proposed question trail for the jury, to make a minute recording the nature of the dispute and the judge's reasons for adopting the trail ultimately used.

Essential reading for trial lawyers

Thanks to Peter Tillers for bringing attention to a paper on DNA evidence that is essential reading for trial lawyers, particularly defence counsel: William C Thompson, Laurence D Mueller, and Dan E Krane, "Forensic DNA Statistics: Still Controversial in Some Cases".