David Hicks has marked his 30th birthday in much the same way he has spent every day of the past four years - locked up in Guantanamo Bay.

Back home, his family has been bolstered by messages of support for the terror suspect.

"To us it's a special occasion turning 30, just like turning 21, and we were probably hoping that he'd be back with us by now," his father Terry said.

Mr Hicks said complete strangers had contacted the family and stopped him in the street to pass on their best wishes .

"We've been approached by people wishing us good luck, even in the supermarket," Mr Hicks told AAP.

"A lot of people know it's his birthday.

"It's been unbelievable and the public support we've had has been excellent."

Hicks, an Australian-born convert to Islam, has been held at the US naval base in Cuba since shortly after he was captured fighting with the Taliban in Afghanistan in the immediate aftermath of September 11.

He will face a military commission - possibly in the next few weeks - to answer charges of aiding Taliban fighters in Afghanistan in late 2001.

He has pleaded not guilty to charges of attempted murder, aiding the enemy and conspiracy.

Mr Hicks said it was the fourth year in a row that his son had missed celebrating his birthday with family and friends in Adelaide.

Instead, his son would probably be locked inside his cell at Guantanamo Bay.

"They keep him locked up for 23 hours a day, so it's a bit hard for him to celebrate," Mr Hicks said.

There are fresh calls for Hicks to be brought back to Australia for trial, although the federal government says he will walk free if he does because he could not be charged under Australian laws existing at the time.

Liberal backbencher Judi Moylan has come out publicly calling for the government to ensure Hicks gets a fair trial ahead of a coalition party room meeting discussion about his fate on Tuesday.

Former High Court judge Mary Gaudron last week joined critics of the US military commission process established to try the Adelaide-born Muslim convert, saying it is clear Hicks has not committed an offence under US law.

Three US prosecutors have now quit the commission process, claiming it is unfair.

Labor says the government is ignoring the widespread criticism of the military commission process.

"Why can't we demand for this man, in the same way we do for everybody else, a fair trial?" Labor's attorney general spokeswoman Nicola Roxon told the Ten network.

She rejected Prime Minister John Howard's assurances that the allegations of bias against the military commission trial process have been adequately investigated by the Pentagon.

"I mean, really, you don't ask the school yard bully if they've actually been picking on anybody. It seems to me that this is getting a little bit silly," she said.

Greens Senator Bob Brown plans to move a motion in the upper house on Tuesday which would call on the United States to repatriate Hicks immediately.

Mr Hicks again called for his son's trial to be before a court.

"The only way David is going to get a fair trial is in a proper court system," he said.

"The commissions are not set up to find someone not guilty - they're there to find someone guilty and put them away."

Click Here for David Hicks Case Information

Two former US prosecutors say the military commission process under which Australian David Hicks will be tried is flawed, with juries selected to ensure conviction.

In leaked emails obtained by Australia�s ABC network, prosecutor Major Robert Preston said some of the commission�s cases were "marginal".

"I consider the insistence on processing ahead with cases that would be marginal even if properly prepared to be a severe threat to the reputation of the military justice system and even fraud on the American people," his email said.

In another leaked email, a second prosecutor, Captain John Carr, also expressed misgivings to a superior.

"I expected there would at least be a minimal effort to establish a fair process and diligently prepare cases against significant accused," he wrote.

"Instead I find a half-hearted and disorganised effort � to prosecute fairly low-level accused in a process that appears to be rigged."

Captain Carr claimed allegations of abuse of detainees had been ignored, evidence had disappeared and prosecutors had offered advice to the appointing authority.

He also said he�d been told the juries deciding the cases would be stacked.

"You have repeatedly said to the office, the military panel will be hand-picked and will not acquit these detainees and we only needed to worry about building a record for the review panel," his email said.

Hicks's military lawyer Major Michael Mori said he was shocked.

"I would be very surprised if the Australian government was provided any of this information at the time they were negotiating and looking at the military commission system to see if it was appropriate or not," he told ABC radio.

But Brigadier General Thomas Hemingway, legal adviser to the military commissions, said the Pentagon had conducted its own investigation and found no legal or ethical problems.

He said the office of the Department of Defence Inspector General conducted a two-month long inquiry and concluded the allegations raised were the result of miscommunications and personality conflicts.

"We found no evidence of any criminal misconduct," he told ABC radio.

He also said there had been a constant exchange of information with the Australian embassy in Washington and rejected the claim juries would be hand-picked to ensure convictions.

Australian Attorney-General Philip Ruddock said US officials told him they had substantial evidence against Hicks, whose military trial will begin within weeks.

He is accused of fighting alongside the Taliban in Afghanistan.

SOURCE: World News

A detainee is escorted to interrogation by US military guards at Camp X-Ray at Guantanamo Bay US Naval Base

The New York Times newspaper and the Australian Broadcasting Corporation are reporting that two former prosecutors say U.S. military commissions set up to try detainees at Guantanamo Bay have been rigged against defendants.

Both news organizations said Monday they had obtained leaked e-mail messages written by the military prosecutors more than a year ago. In those emails, the prosecutors complained to their military superiors that the trial system was secretly set up to improve the chance of convictions, and were unfairly slanted against defendants.

The messages were sent to prosecutors' supervisors in March of last year, just three months before Australian inmate David Hicks was charged. Mr. Dicks was captured by U.S. forces while allegedly fighting with the Taleban in Afghanistan in 2001.

The Australian government says it will investigate the prosecutors claims.

Some information for this report provided by AP, Reuters.