The Law Commission has proposed ditching trials by a full jury of 12 in favour of trials by a judge and two semi-professional jurors to allow more evidence, such as previous convictions, to be used.
In a consultation paper on alternative trial systems, the commission sets out a range of proposals for change, especially in sexual offending cases.
They include replacing a full jury with a judge alone or a judge with two full-time jurors who would be trained in criminal procedure.
The paper said trials heard by either a judge alone or a judge with two trained jurors would allow many of the rules of evidence to be dispensed with, because a smaller pool of fixed-term jurors could be trained in criminal trial procedures in a way normal jurors could not.
Research showed jurors had "an array of myths and prejudices" that resulted in laws restricting the use of evidence which could be prejudicial, but professional jurors could be taught to put their own prejudices aside.
An example of the evidence that could be included under such a system was previous convictions of defendants. In August 2007, a law change allowed previous convictions to be used in some cases, but only when the strength of the evidence outweighed any risk of prejudice.
That change followed controversy after the acquittals of former policemen Brad Shipton, Bob Schollum and Clint Rickards on sex charges in the Louise Nicholas case. After the trial, it was revealed that Shipton and Schollum were already in prison after being found guilty in 2005 of the 1989 pack rape of a young woman in Mt Maunganui - information that could not be disclosed to the Nicholas jury.
Another proposal in the paper is giving judges more control over a trial - including deciding who would give evidence and questioning witnesses. Law Commission president Sir Grant Hammond said it could create fairer trials, rather than relying on the skill and resources of the lawyers, and prevent aggressive questioning of witnesses.
The paper focuses mainly on sexual offences, saying many victims and defendants find the current adversarial system "alienating and disempowering".
It proposes a specialist "sexual violence court" for those who plead guilty. That court would allow reduced sentences for offenders who underwent treatment successfully.
Sir Grant said a specialist court would be able to respond in a more flexible way than at present. Another option was for a separate system in cases where a victim did not want a full criminal trial, where the defendant was not considered a threat to wider public safety and had agreed that sex had taken place, such as date rape cases.
Law Commission consultant Dr Warren Young said alternative systems could help increase the rate of reporting of sex offences, which was low because many were put off by the prospect of a trial.
Difficulties in proving sexual offences meant the number of prosecutions was low and only about 42 per cent resulted in convictions. Some proposals were aimed only at sexual offence cases while others - such as the proposal for a jury of two - could be used more widely.
The Government ordered the paper in 2011 after the report of the Taskforce for Action on Sexual Violence, which agreed with a 2008 Law Commission report on the disclosure of previous convictions in which the commission recommended consideration of alternative systems, especially in sex cases.
Submissions are due by April 27 and can be made at www.lawcom.govt.nz/alttrials
* Trials are decided by either a judge alone or a judge with two appointed "semi-professional" jurors, trained in criminal procedure.
* Judges, rather than lawyers, control trials including calling witnesses.
* Victims can request review of decisions to drop or amend charges, fast-tracking cases with vulnerable witnesses.
* Defendants' evidence given at the start of a trial instead of after the prosecution.