Planned changes to the NSW Evidence Act that will weaken the right to silence, likely to come before parliament in a fortnight, have attacted criticism from the legal fraternity, the NSW Opposition and cross-benchers.

The changes will mean that if an alleged criminal remains silent when questioned by police, but then produces so-called "mystery evidence" during a trial, jurors may infer criminal conduct. As a result, the standard police caution will be changed to:

"You are not obliged to say or do anything unless you wish to do so. But it may harm your defence if you do not mention when questioned something you later rely on in court."

The current situation across all Australian states and territories is that there is no obligation for an accused to participate in the investigative process, other than in special cases or when compelled.

When the changes were originally announced in August 2012, Police Commissioner Andrew Scipione said they were a way of overcoming the "wall of silence" that the police encounter while investigating drive-by shootings and other gun crime. The reforms would also help overcome "surprise alibis", Scipione told the ABC.

But NSW shadow attorney-general Paul Lynch does not believe the Government’s case to change the law is sufficient.

"The right to silence has been a principle of our legal system for several hundred years," he told NM. "The government bears a substantial onus in justifying such a change. They haven’t, in my view, got anywhere yet near to discharging the onus."

"If the law is aimed to break the ‘wall of silence’ claimed to inhibit investigations into drive-by shootings that it’s fundamentally misconceived. This [proposed]law is aimed at those guilty of offences — when what they need is information from witnesses, as opposed to offenders."

The NSW Bar Association is also concerned with the stated reasons for changing the law. President Phillip Boulten has claimed the proposed changed are "the most drastic changes to criminal procedure in the last century".

Boulten, who is also a senior figure in the Labor Party, says Scipione is engaging in "political spin" and that the wall of silence "has got nothing to do with it".

"It won’t assist the police with this so-called wall of silence. People who have information aren’t coming forward. There is already a law if you are a witness and are ‘concealing a serious criminal offence’. That law’s purpose is to break the wall of silence", Boulten told NM.

Vulnerable suspects will be most acutely affected by the reforms, according to Boulten. "It changes the balance between prosecution and defence to the detriment of the accused," he said. "The proposed changes will have a disproportionate effect on vulnerable suspects, who don’t have the wherewithal to know what is important when answering questions in a police station".

NSW Greens MLC David Shoebridge also has concerns about the expansion of police power:

"The State Government has more than adequate laws and existing police powers to deal with organised crime, if that was the real issue. These include the powers of the NSW Crime Commission. The Crime Commission is a secret and powerful investigative body that already has compulsory administrative detention and coercive powers."

Shoebridge also denies that "surprise alibis" warrant a far-reaching change to the law. "First of all, the late alibi, when you look at the facts, is almost never successful. Defendants are already required to give notice of alibi evidence at least 42 days before trial.

"If there is a concern that defendants are flouting the requirement to give notice of alibis, then a far more focused reform would be to only allow an adverse finding from prior silence where late alibi notice is given."

The Police Association of NSW has been campaigning for these reforms for nearly a decade — well before the recent spate of gun violence.

In 2006, the Police Association of New South Wales’s then secretary Peter Remfrey told the ABC, "what we’re suggesting, which is the British model, is that courts are entitled to say, well, if you were innocent of crime and you had evidence at the time that you’re now choosing to rely on, why in the name of goodness didn’t you provide it".

New South Wales police also sit on the board of the Australian Crime Commission, whose ambit is to "support and complement the law enforcement community and broader government efforts to reduce the threat and impact of serious and organised crime". The ACC are already significantly involved in firearms matters.

The Government initially came out strong in August last year and indicated the legislation would be in place as early as October 2012. They are now tight-lipped as to their position, following private consultations.

Far from his emphatic announcement flanked by the Premier and Police Commissioner, the Attorney-General is reticent to discuss the reforms. A spokesperson told NM last week that "The Government has consulted widely about the proposed changes and will be announcing its position shortly."

Without the support of the Greens, the NSW Government must negotiate with the Christian Democrats and Shooters and Fishers Party if the legislation is to make it through both houses.

Milton Caine, policy co-ordinator for the Christian Democrats seems to be convinced that legislative reform isn’t needed, claiming policing standards may need the attention.

"The problem is that the police don’t always have their best investigation techniques and they rely on only being followed up with the assigned officer when he/she is on duty. Their processes may need to improved and they would get better outcomes than changing this law," Caine said.

If successful, the new laws would be a first for any Australian state or territory. The NSW Bar Association "plans to lobby Opposition and cross-benchers to defeat the bill". Boulten understands that laws could be ready for parliament as early as next week.

The Police Commissioner’s office declined repeated requests for a response by New Matilda over a five-day period.