Key Points:

The Law Commission wants a Government inquiry into the way alleged sex offenders are tried following the Louise Nicholas case, saying the present trial system is "brutalising and distressing" for complainants.

The call was made as the commission released its report on whether previous convictions of defendants should be disclosed to juries.

Law Commission president Sir Geoffrey Palmer said there were wider "disturbing features" about the trial process for sexual offences and recommended a Government inquiry into whether an alternative model would be preferable to the present adversarial model.

The report said the commission had "lingering worries" about the fairness of the traditional court system for dealing with sex cases after speaking to Mrs Nicholas and others.

The concern was reinforced by a submission from a retired Court of Appeal judge, Justice Ted Thomas.

"He told us that the nature and impact of the trial in sexual cases on complainants is a brutalising and distressing experience in which the complainant is effectively put on trial," the report said.

Sir Geoffrey said there was also concern at the high number of acquittals in rape cases. The Taskforce on Sexual Violence, which was now under way, should look at the issue further and decide on options which a further, separate inquiry could consider.

Justice Minister Annette King said yesterday that the taskforce was considering the issue and would release a discussion document on possible alternatives to adversarial trials in sexual violence cases.

The Network for Ending Sexual Violence Together also told the commission that it had concerns about the low conviction rate for rape in New Zealand and believed victims were deterred from reporting offences because of the ordeal they were then put through.

Justice Thomas has previously called for changes to the system and made similar comments in an article in the New Zealand Law Journal in May.

Sir Geoffrey said any inquiry should also consider a wider range of cases. He did not want to prejudge the outcome of any inquiry by suggesting other systems or which crimes could be covered, but he said juvenile cases and paedophilia were also problems.

Law Commissioner Val Sim said there had been attempts to improve the system for complainants - including allowing screens to be used for some witnesses and requiring the leave of the judge before cross-examination could be made on a complainant's sexual history.

However, submissions to the Law Commission had said it was still a concern.

"We don't know if there is a better system, but we ought to look and see if there is."

The Government asked the commission to look into the law regarding evidence of previous convictions after public disquiet following 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 pack rape of a young woman in Mt Maunganui in 1989 - information that could not be disclosed to the jury previously.

Sir Geoffrey said the law had subsequently been loosened and the commission would monitor the effects of the change and report back to the Government in February 2010.

He said the Evidence Act 2006 had been interpreted by the Court of Appeal as allowing judges to use such evidence after weighing up the evidential value of prior convictions against the potentially prejudicial effect to the defendant.

"If someone digs up the body of a baby in a back garden, and then finds evidence that the person had lived in three other houses where bodies of dead babies were found, that is similar fact evidence and may be admissible."

He said the commission did not believe there should be a black and white law which either automatically allowed or banned the use of such evidence.

Annette King said she agreed with the commission's conclusion that new laws relating to the admissibility of evidence of prior convictions didnot need to be changed at thispoint.