New Zealand First has put the brakes on proposals to overhaul how rape trials are run following concerns about the impact on fair trial rights.
The Sexual Violence Legislation Bill was supported by all parties at the first reading last year and was hoped to be passed into law earlier this year.
But Justice Minister Andrew Little confirmed that the bill's progress has stalled until issues raised by New Zealand First can be resolved.
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Those issues stem from concerns raised by defence lawyers that the bill would compromise a defendant's right to a fair trial, which is enshrined in the Bill of Rights Act.
"The Defence Bar has started up a lobby campaign. I think it's being somewhat alarmist," Little told the Herald.
"But in any event those issues are being discussed between the governing parties at the moment."
NZ First Cabinet Minister Tracey Martin said the caucus was "still gathering information" as her discussions with both Labour and the Greens continued.
She completely rejected any speculation that NZ First had reversed its support for the bill because of Labour opposing her proposal to use internet service provider filters to ban porn websites for those under 18.
The Sexual Violence Legislation Bill aims to make the court process less traumatic for complainants, but the NZ Bar Association, the Criminal Bar Association and the Auckland District Law Society have raised two main concerns.
The first is the entitlement for complainants to be cross-examined via pre-recorded video, which would protect them from the potentially intimidating experience of giving evidence in front of a jury and the accused.
The second is introducing a higher threshold before evidence can be used about the complainant's sexual disposition, reputation or experience, including any sexual history with the accused.
The National Party, in its minority view in the select committee report on the bill, said the former issue defeated the purpose of the bill; if new evidence emerged after the pre-recorded video and the complainant had to give evidence a second time, it could be a doubly traumatic experience.
National also opposed the higher threshold for evidence about the sexual history between a complainant and a defendant.
In submissions on the bill, defence lawyers argued that this sexual history was often central to the defence's case, but under the bill it would be assumed to be irrelevant.
The defence could apply for a judge to review the intended evidence, but in trying to prove its importance, the defence would have to "show its hand" by telling the judge and the prosecution the nature and scope of its questions.
The bill is in part based on recommendations from the Law Commission, which said the higher threshold was appropriate because it put the focus on the relevancy of the evidence rather than the relationships of those involved.
Previously granted consent does not mean future consent should be assumed, the commission said.
National's courts spokesman Chris Penk said the caucus is yet to make a decision on how the party would vote on the bill if its concerns were not addressed.
In the meantime, lawyers vehemently opposed to the bill are lobbying politicians of all stripes.
A letter signed by 20 Wellington women criminal defence lawyers has been sent to the Green Party, urging the bill to be changed to reflect National's proposed changes.
Top of the list of signatures was Elizabeth Hall, vice president of the Criminal Bar Association, whose submission on the bill said that it "crushes defendants' rights to offer an effective defence".
Little rejected this, saying the bill balanced fair trial rights with making the process less hostile for complainants, who often don't come forward at all because of a lack of trust in the system.
"I think the bill achieves that balance but that is obviously a matter still subject to debate."
He wouldn't rule out the Government progressing the bill with National's proposed changes on the basis that it would still improve the status quo.
"In the end, it's going to be a judgment that the governing parties will make collectively, and those discussions are still underway."