Chapter 9
Conviction evidence

Conviction evidence in criminal cases

9.4Section 49 provides:

49 Conviction as evidence in criminal proceedings

(1) Evidence of the fact that a person has been convicted of an offence is, if not excluded by any other provision of this Act, admissible in a criminal proceeding and proof that the person has been convicted of that offence is conclusive proof that the person committed the offence.
(2) Despite subsection (1), if the conviction of a person is proved under that subsection, the Judge may, in exceptional circumstances,—
(a) permit a party to the proceeding to offer evidence tending to prove that the person convicted did not commit the offence for which the person was convicted; and
(b) if satisfied that it is appropriate to do so, direct that the issue whether the person committed the offence be determined without reference to that subsection.
(3) A party to a criminal proceeding who wishes to offer evidence of the fact that a person has been convicted of an offence must first inform the Judge of the purpose for which the evidence is to be offered.

9.5The fact that a person has been convicted of an offence is admissible as conclusive proof that they committed it. This is subject to the fact of conviction not being excluded by any other provision in the Act. To enable the judge to determine whether other provisions in the Act exclude the use of such evidence (such as the propensity or veracity provisions), the party seeking to offer the evidence must inform the judge of the purpose for which they seek to use it. In “exceptional circumstances” the judge may allow a party to offer evidence tending to prove that the person convicted did not commit the offence.

9.6The Law Commission has received a submission concerned that s 49 can potentially deprive a co-defendant of running a defence that would otherwise be available to them, and relieve the Crown of the burden of proving essential elements of a charge. One situation is a case involving multiple defendants in which one defendant pleads guilty prior to trial. If the prosecution case is that the remaining co-defendants committed the offences in conjunction with that defendant, evidence of the conviction can be relevant to essential elements of the charges in relation to the remaining co-defendants.

9.7 This risk is illustrated by the case of R v Bouavong in which a co-defendant pleaded guilty to 36 counts of supplying methamphetamine, conspiring to supply methamphetamine, and engaging in money-laundering.594 The Crown sought to offer evidence of the conviction that followed this guilty plea in the trial of the remaining co-defendants. The High Court was concerned that admitting this evidence would prove “key ingredients of the Crown case regarding each alleged transaction; namely, that the substance in question was methamphetamine and that supplies of that controlled drug occurred on the particular dates alleged”.595 The Court excluded the conviction evidence under s 8, holding that:596

Offering evidence of previous convictions in the circumstances and manner which the Crown propose would essentially deprive the defendants of their opportunity to test the evidence offered against them on essential elements of the charges. In that sense, it would deprive them of their ability to offer an effective defence of their choosing. That the convictions in this case have come as the result of guilty pleas serves to accentuate the unfair prejudice which would occur – the supposed evidence of guilt would remain untested by any Court.

9.8 Similar reservations led to Potter J excluding conviction evidence under s 8 in R v Tanginoa.597 That case also involved a co-defendant pleading guilty to a charge of conspiracy to import methamphetamine. Potter J was concerned that:598

… the evidence that establishes the essential elements of the charges against them has not been tested at trial and has not been admitted by the three accused. They are entitled to offer an effective defence which challenges both that a conspiracy has been established, and, if so, that the accused in question was a party to it.

9.9 Another situation that has given rise to concern is where a co-defendant is tried as a party to an offence after the principal defendant is convicted (either in an earlier trial or following a guilty plea). As secondary liability is contingent on a principal offence being committed, a co-defendant cannot be convicted as a party to the offence if the principal offence itself is not proved.599 However, a co-defendant can potentially be deprived of the opportunity to advance a legitimate defence (that there was no principal offence to which their liability as a party could attach) if evidence of the principal defendant’s conviction is offered as conclusive proof that the principal offence occurred.
9.10This issue was highlighted in McNaughton v R in which the Crown sought to offer evidence of a principal defendant’s conviction for murder in the trial for the remaining co-defendants who were charged as parties (the trial of the principal defendant and co-defendant was severed for evidentiary reasons).600 The co-defendant sought to offer evidence under the “exceptional circumstances” proviso in s 49(2) that the principal defendant acted in self-defence (a defence that the principal defendant unsuccessfully advanced at his own trial), and that they therefore could not be liable as parties.
9.11The trial judge held that evidence to counter the principal defendant’s conviction was inadmissible, and the co-defendant appealed to the Court of Appeal. The Court heard the appeal in conjunction with that of the principal defendant, who had also appealed his conviction. The Court allowed the principal’s appeal on the murder charge and ordered he be retried, together with the co-defendant, in a new trial.601 Its comments in relation to the co-defendant’s appeal were therefore brief. The Court agreed with the trial judge that the certificate of conviction was admissible and that there were no extraordinary circumstances for the purposes of s 49(2) to allow the co-defendant to offer counter-evidence. In doing so, O’Regan P for the Court specifically cited his concern about the possibility of a second jury reaching a different conclusion, based on different evidence, as to the guilt of the principal defendant.602
9.12These cases demonstrate the particular difficulties in the use of conviction evidence under s 49 in trials of co-defendants. Although we acknowledge that s 49 can, in certain circumstances, affect a co-defendant’s ability to run certain defences, there are a number of safeguards in place to protect the co-defendant’s right to a fair trial. First, admissibility under s 49(1) is made expressly subject to the other admissibility provisions in the Act. As R v Bouavong demonstrates, this includes the fundamental admissibility provisions (ss 7 and 8) enabling a co-defendant to challenge admissibility on the grounds that its probative value is outweighed by its unfair prejudicial effect. As the High Court stated in R v Nguyen:603

Section 49 is a gateway to introducing evidence of conviction. It is not, as I have said, a substitute for the s 8(1) balancing exercise. This approach is reinforced by the words “if not excluded by any other provision of this Act” used in s 49(1).

9.13The right of a defendant to offer an effective defence forms part of that balancing process.604 This right has been explicitly referred to by the courts when excluding conviction evidence that the Crown has sought to adduce under s 49.605 Second, a co-defendant may seek to offer evidence to counter the conviction evidence if they can prove there are “exceptional circumstances” under s 49(2). Sections 8 and 49 therefore provide avenues for a co-defendant to challenge the use of conviction evidence if it would impact on his or her right to a fair trial. In the absence of clear case law demonstrating that these avenues are deficient (indeed, our assessment of the case law is that courts are acutely conscious of a defendant’s right to offer an effective defence when making decisions about the admissibility of conviction evidence), we recommend no legislative change at this time. However, we recommend that the effect of these provisions on co-defendants continue to be monitored for the next five year review.

R18 We recommend that the effect of s 49 on co-defendants be kept under review with any problems identified to be considered at the next five year review.

594R v Bouavong (No 7) [2012] NZHC 524.
595At [63].
596At [75].
597R v Tanginoa [2012] NZHC 3121.
598At [47].
599Bruce Robertson (ed) Adams on Criminal Law – Evidence (online looseleaf ed, Brookers) at [CA66.04].
600McNaughton v R [2011] NZCA 588.
601At [65].
602At [62].
603R v Nguyen (No 2) HC Auckland CRI-2008-092-17198, 17 September 2010 at [19].
604Evidence Act 2006, s 8(2).
605R v Bouavong, above n 594 at [75]; R v Tanginoa, above n 597, at [47].