The exclusion of prison informant evidence for unreliability in New Zealand

AuthorAnna High
DOI10.1177/13657127211011236
Published date01 July 2021
Date01 July 2021
Subject MatterArticles
Original Research Article
The exclusion of prison
informant evidence for
unreliability in New Zealand
Anna High
The University of Otago, Dunedin, New Zealand
Abstract
Prison informant or ‘jailhouse snitch’ evidence is a notoriously unreliable category of evidence.
In light of reliability concerns, the New Zealand Supreme Court has adopted a progressive
approach to the exclusion of prison informant evidence, centred on greater use of general
exclusionary provisions as a threshold of reliability for the admission of suspect evidence. In so
doing, the court has shifted the emphasis from deference to the jury as arbiter of ultimate
reliability and towards more robust judicial gatekeeping as a safeguard against false testimony.
This article critically analyses the New Zealand approach, including by way of comparison with
Canada, Australia and England and Wales. The New Zealand approach is presented as a
principled and important example of adapting fundamental evidentiary principles and provisions
in line with emerging social science evidence. However, in light of the general concerns sur-
rounding this class of evidence, ultimately further safeguards are still needed
Keywords
comparative, exclusion, prison informants, probative value, reliability
Introduction
Prison informants, more pejoratively known as ‘jailhouse snitches’, have played a long and troubling
role in criminal justice systems around the world, including in Aotearoa New Zealand. Prison informant
evidence refers to evidence of a defendant statement purportedly made to another person while both
persons were detained, and off ered by that other person (the in formant or ‘snitch’) as prosecu tion
evidence. Typically, the defendant’s statement is inculpatory, such as the classic ‘cellmate’s confession’.
Importantly, prison informant evidence is frequently offered by informants in exchange for an incentive,
such as lenience at sentencing. This is a notoriously unreliable class of evidence which has been shown
to be a common factor in cases of known wrongful convictions. Despite this inherent unreliability, New
Zealand, consistent with other common law jurisdictions, has historically taken a permissive approach to
Corresponding author:
Anna High, University of Otago PO Box 56 Dunedin, 9054 New Zealand.
E-mail: anna.high@otago.ac.nz
The International Journalof
Evidence & Proof
ªThe Author(s) 2021
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DOI: 10.1177/13657127211011236
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2021, Vol. 25(3) 217–238
prison informant evidence. This category of evidence is not addressed by any specific exclusionary rules
and is not presumptively inadmissible. Instead, concerns relating to the credibility and reliability of
prison informants are generally left to a cautioned jury, to be assessed in light of cross-examination of
the informant and the evidence as a whole at trial.
However, all modern evidence codes place some limits on the admission of relevant evidence. Those
limits are applied by the judge in what is commonly known as the gatekeeping function. As such,
although prison informant evidence is not presumptively inadmissible, and despite its obvious and direct
relevance to guilt,
1
there is scope under evidence law for its exclusion based on reliability concerns. And
in a recent landmark decision, the New Zealand Supreme Court has taken a comparatively progressive
approach to that scope. Expanding on a Court of Appeal ruling
2
that judges may exclude prison
informant evidence for unreliability in cases of exceptional reliability concerns, the Supreme Court in
WvRessentially treated all such evidence as exceptionally concerning and warranting close scrutiny
under the rubric of probative value as weighed against risk of illegitimate prejudice.
3
In so doing, the
court has shifted the emphasis away from deference to the jury as arbiter of ultimate reliability, and
towards robust judicial gatekeeping as arbiter of threshold reliability. With this shift in emphasis, New
Zealand has also parted ways with the more conservative Australian and English approaches to prison
informant evidence admission, taking an important step towards recognising and redressing the limits of
juries in assessing reliability concerns—at least in relation to this class of evidence, and potentially with
implications for the scheme of evidence law more generally. The New Zealand approach aligns with a
long line of international scholarship calling on judges to make greater use of general exclusionary
provisions to ensure that patently unreliable prison informant evidence does not reach the jury and is an
important example for other more conservative jurisdictions. It also goes some way towards addressing
the concerns surrounding this class of suspect evidence, however, ultimately further safeguards are
needed and other possible avenues of reform should be explored.
Prison informant reliability concerns: a primer
A useful starting point for the analysis of prison informant evidence in New Zealand is the case of David
Tamihere. In April 2020, Tamihere was granted a Royal Prerogative of Mercy, 30 years after he was
found guilty of murdering Sven Urban Ho¨glin and Heidi Paakkonen, two Swedish backpackers. He had
been released on parole 10 years earlier, having served 20 years for the crimes. Tamihere has always
maintained his innocence. The Crown case against Tamihere was wholly circumstantial, the bodies of
the tourists not having been found a t the time of trial.
4
The Crown built a three-part case a gainst
Tamihere, with one part based on the evidence of three prisoner informants. One of those informants
later publicly recanted his evidence and was ultimately convicted of perjury as a result.
5
Of the other two
informants, one was a regular police informant who had previously struck a deal with police when facing
drug charges. The other, who has since died in a car crash, offered evidence that Tamihere had confessed
to cutting up the bodies, evidence that was contradicted when the bodies were found intact a year after
Tamihere’s conviction.
1. As discussed below (n. 57 and accompanying text), this relevance depends on whether the informant is speaking truthfully
about the defendant’s statement. Provided this is so, a defendant confession will be logically and directly relevant to guilt.
2. RvHoggart [2019] NZCA 89.
3. WvR[2020] NZSC 93. WvRwas an appeal/cross-appeal from two related Court of Appeal decisions, RvHoggart [2019]
NZCA 89 and W (CA226/19) vR[2019] NZCA 558. These decisions dealt with a number of pre-trial admissibility questions
pertaining to the Red Fox Tavern case, a 1987 armed robbery/murder for which two men were arrested in August 2017. See
further High (2020).
4. Harris vTaylor [2018] NZCA 393 at [5].
5. Arthur William Taylor vWitness C [2017] NZHC 2610.
218 The International Journal of Evidence & Proof 25(3)

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