Updated

A U.S. military commission began pretrial motions for an Australian allegedly caught fighting with the Taliban (search) in Afghanistan by denying a defense request for expert witnesses and by beginning debate on whether the charges against him constitute war crimes.

Lawyers for David Hicks (search) want charges against the 29-year-old to be dropped, arguing Monday that his scheduled Jan. 10 trial will be unfair since the commission panel has been reduced from five members to three.

Hicks' lawyers also maintain the allegations against their client do not constitute war crimes and that other unprecedented charges have never been litigated.

Hicks has pleaded innocent to charges of attempted murder, aiding the enemy and conspiracy to attack civilians, commit terrorism and destroy property. He could be sentenced to life imprisonment if found guilty.

His trial is part of the first U.S. military commissions since World War II.

Dealing an early blow to the defense, the presiding officer, Army Col. Peter E. Brownback (search), denied a request for six witnesses to be called but said witnesses for trials would be considered on a case-by-case basis.

The decision sparked a heated exchange between prosecutors, who said witnesses would create a legal sideshow, and the defense, who said the experts could only help.

"Obviously we were disappointed," said Hicks' civilian defense lawyer, Josh Dratel. "For lay persons, there is a tremendous amount to absorb. That's why we wanted a number of experts."

Prosecutor Marine Lt. Col. Kurt Brubaker argued the panel should interpret the law.

Whether the charges Hicks faces fall under the laws of war or are charges the commission can legally hear is another area that Hicks' defense team is challenging.

The defense claims Hicks should not be charged with aiding the enemy because the Australian citizen was already considered an enemy when he allegedly joined the Taliban and developed ties to the al-Qaida terror network. His attorneys also maintained that to aid an enemy implies that one has to have allegiance to the country declared an enemy.

"Hicks is an Australian citizen with no allegiance to the United States," said Army Maj. Jeffrey Lippert, another member of Hicks' defense team. "This concept of being an enemy and aiding the enemy has never existed before."

His attorneys also argue that the attempted murder by an unprivileged belligerent charge is not applicable since Hicks is accused of taking up arms against U.S. and coalition forces in Afghanistan. The charge would only have been merited had he tried to hurt civilians protected under laws of war, as opposed to military personnel, said Marine Corps Maj. Michael Mori.

Decisions have yet to be made, but challenges in August to the panel's impartiality resulted in the dismissal of two panel members and one alternate, shrinking the panel to three members — only one of whom has law experience.

Defense attorneys said the dismissals would compromise Hicks' trial, making it easier for prosecutors to get a two-thirds majority with two people versus four before.

The government is working to replace the panel members for the cases of Ali Hamza Sulayman al-Bahlul, a Yemeni accused of developing propaganda for al-Qaida, and Ibrahim Ahmed Mahmoud al-Qosi, a Sudanese accused of being an al-Qaida paymaster.

The reasoning was that the two suspects haven't yet had the chance to challenge the panel members.

Prosecutors say the rules stipulate only three members are needed to hold a commission.

Hicks, wearing a gray suit, glared at panel members throughout the hearing.