Guantanamo Bay, Cuba ? A Yemeni prisoner at Guantanamo Bay accused of serving as a bodyguard for Osama bin Laden refused to participate in military proceedings against him Wednesday, insisting that he would not receive a fair trial.

Ali Hamza Ahmad Sulayman al Bahlul, who had said he was boycotting the tribunal, attended most of the day’s hearing. But after an afternoon recess al Bahlul apparently refused to return.

The presiding military officer said he wasn’t certain how to proceed.

Army Col. Peter E. Brownback said he wasn’t aware of any requirement to force al Bahlul to be present.