Justice Minister Andrew Little is "uncomfortable" with the use of jailhouse informants, saying juries should be told who they are and what they've been promised in exchange for their testimony.
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"We've heard of jailhouse witnesses, particularly when they're giving evidence about so-called confessions, and actually many of them simply haven't stood up," he told Newshub Nation on Saturday.
"If the police insist on bringing witnesses who are current inmates or serving inmates and claim to have heard a confession… the evidence has to include the full circumstances in which that inmate is giving evidence."
The Law Commission is currently reviewing the Evidence Act, and while Mr Little says they aren't specifically looking at jailhouse informants at this time, he believes it would be a "useful area" for them to examine in future.
Jailhouse informants, such as those who provided evidence in the trial of David Tamihere in 1990, have their identities protected and may receive 'inducements' for their testimony, such as reduced sentences.
One of New Zealand's longest serving inmates, Arthur Taylor, successfully pursued a perjury case against one of those "secret witnesses" in the Tamihere trial, who was revealed to be Taylor's fellow inmate Roberto Conchie Harris.
Taylor says the Government should restrict the use of jailhouse informants in court because their testimony is always motivated by self-interest, and not public service.
"I've yet to meet one involved in any of these cases, or even hear of one, that has told the truth.
"Let's say I trotted into court for one of my cases with a witness and it turned out I'd paid him $10,000 or $20,000. Some of these guys can be bought very cheap. Right? What do you think the judge would say? He'd say, 'Get out of here, Taylor. This guy's bought and paid for.'"
Taylor suggests we adopt a legal model like Canada, where a conviction is not possible purely based off the testimony of a jailhouse informant and any evidence provided by prisoners has to be corroborated.