A Yemeni man accused of being Osama Bin Laden's bodyguard has appeared before a military tribunal at the US detention facility in Guantanamo Bay, Cuba.
The first prisoners arrived at Guantanamo Bay four years ago
Ali Hamza al Bahlul, who has said he is a member of al-Qaeda, went before the tribunal's pre-trial hearing four years to the day since the camp was set up.
Mr Bahlul refused a lawyer, saying: "There's going to be a tribunal of God on the day of judgement."
Rights group Amnesty International repeated calls for the camp to be shut.
Mr Bahlul is charged with conspiring to commit war crimes by being a bodyguard of Bin Laden and making training videos for militants. His trial is expected to begin on 15 May. He spoke out in front of the military tribunal, saying in Arabic that he did not recognise its authority.
"Do what you have to do and rule however you have to rule... God will rule based on justice," he said.
He ended his outburst with one word in English - "boycott".
The pre-trial hearing against another man, Canadian Omar Khadr, 19, was also scheduled to convene on Wednesday.
Mr Khadr has been charged with murdering a US medic with a grenade in Afghanistan when he was only 15.
If convicted, Mr Bahlul and Mr Khadr could face life in prison.
Their cases have gone ahead even though the trials of other Guantanamo detainees have been halted while the US Supreme Court decides if US President George W Bush has the authority to establish such tribunals.
The Bush administration argues that it needs flexibility in dealing with the war on terror and terrorists cannot be treated as if they are just another criminal defendant.
The military tribunals have been criticised for failing to give suspects a fair trial.
Only nine of the camp inmates have so far been charged
Amnesty said 500 detainees continued to be held without charge or trial at Guantanamo Bay and repeated its call for the facility to be shut.
Amnesty said there were mounting allegations of appalling conditions, torture and ill-treatment of detainees at the camp.
The group highlighted the case of Jumah al-Dossari, a 32-year-old Bahraini who was taken to Guantanamo Bay in January 2002.
His lawyer said Mr Dossari had been urinated on, threatened with rape and had his head repeatedly smashed against the floor. The claims have been denied by the US government.
He had reportedly attempted to commit suicide 10 times, the rights group said.
Another detainee, Sami al-Hajj, a Sudanese cameraman for Arab satellite TV network al-Jazeera, had been subjected to severe physical, sexual and religious abuse over the last four years, his British lawyer Clive Stafford-Smith said.
Amnesty's UK Campaigns Director, Stephen Bowen, called the situation at Guantanamo Bay "shocking".
"There's no middle ground regarding Guantanamo. It must be closed and there must be an investigation into the dozens of torture reports that have emerged since 2002," he said.