Give me the death penalty, says the 'mastermind' of September 11

In his first public appearance since he was seized in his pyjamas five years ago, the self-described mastermind of the September 11 attacks, Khalid Sheikh Mohammed, told a military court in Guantanamo Bay yesterday that he would welcome the death penalty.

The hearing descended into farce at times as the senior al-Qa'ida operative sang verses from the Koran in Arabic – pausing to translate them in English – and lodged an objection about the courtroom artist making his nose look too wide.

Mr Mohammed also announced that he was sacking his military-appointed lawyers. Mr Mohammed, who was tortured by waterboarding after his capture in Pakistan, declared: "I will represent myself. [I]... cannot accept any attorney who is governed ... [by law] ... rather than the Lord of the law."

Informed by Judge Ralph H Kohlmann that he faced the death penalty for organising the 2001 attacks on America, he said: "Yes, this is what I wish, to be a martyr for a long time. I will, God willing, have this, by you."

Fearing that the military courtroom would be used for propaganda on behalf of al-Qai'da, only selected reporters were allowed to watch the trial unfold on closed-circuit television, which had a 20-second delay to enable censors to act.

Witnesses said Mr Mohammed was sporting a long grey beard and military-issue black sunglasses. He was wearing a neat, unblemished white tunic and turban but he asked the courtroom artist to use the widely-used photograph of him looking dishevelled when he was seized in Pakistan as a guide and make his nose look as it did in that picture.

According to US military transcripts of a hearing last year, Mr Mohammed said he had overseen "from A to Z" the attacks that killed 2,973 people in New York, Washington and rural Pennsylvania more than six years ago. But yesterday he backtracked, saying in broken English: "They mistranslated my words and put many words in my mouth."

He and four other defendants were moved yesterday morning from their cells to a specially built military courtroom in Guantanamo Bay for their first court appearance since being captured. The exact location of Mr Mohammed's cell is a secret and he has not been seen in public since being photographed on his capture.

The five men were arraigned on war crimes charges. Mr Mohammed smiled and chatted with those at the defence table where Waleed bin Attash, who is accused of recruiting and training some of the 19 hijackers, was sitting. The other defendants are the alleged logistical co-ordinators of the attacks, Ramzi bin al-Shibh, Ali Abd al-Aziz Ali and Mustafa Ahmed al-Hawsawi. Without explanation, charges against another man, Mohammed al-Qahtani, were dropped last month.

Yesterday's arraignments are also a test for the much criticised military tribunals. A Supreme Court ruling is due this month on the challenge that basic human rights have been denied Guantanamo prisoners. Among the questions yet to be resolved is whether waterboarding – which is banned by the US military but not the CIA – constitutes torture, whether confessions obtained by coercion are admissible and what psychological damage the defendants have suffered.

Mr Mohammed's former defence team claim that he may have suffered cognitive impairment after being tortured by the CIA. The Bush administration has already acknowledged that he was waterboarded – a technique that involves strapping a person down while forcing water into his mouth so that he believes he is drowning.

The first military commissions were deemed unconstitutional by the Supreme Court in 2006. Resurrected by Congress, they have remained under a cloud ever since and challenged repeatedly as unconstitutional.