A military judge at Guantanamo Bay has ruled that one of the 9/11 defendants is unfit for trial after a medical panel found that the man’s sustained abuse in CIA custody years earlier has rendered him psychotic.

The judge, Colonel Matthew McCall, said the incompetency finding for Ramzi bin al-Shibh meant the prosecution of his four co-defendants would continue without him. Al-Shibh will remain in custody.

Judge McCall issued his ruling late on Thursday. Pre-trial hearings for the remaining defendants resumed on Friday in the military courtroom at the US naval base on Cuba. No trial date has been set for the case, which has been slowed by logistical problems and legal challenges.

Al-Shibh, from Yemen, is accused of organising one cell of the 19 hijackers who carried out the September 11 2001 attacks, which killed nearly 3,000 people in New York, Washington and Pennsylvania. The attacks were the deadliest of their kind on US soil.

World Trade Center attack
Almost 3,000 people died on September 11 2001 (PA)

The attacks rocked Americans and people around the world. They led the George W Bush administration to take extraordinary steps in what it called a war on terror: invading Afghanistan and Iraq, setting up an extraordinary programme of CIA interrogation and detention, and creating the special prison and military commission at Guantanamo.

A military medical panel last month diagnosed Al-Shibh as having post-traumatic stress disorder with secondary psychosis, and linked it to his torture and solitary confinement during four years in CIA custody after his 2002 arrest.

Al-Shibh has complained for years since his transfer to the US naval base at Guantanamo Bay, Cuba, that his guards were attacking him, including by invisible rays, so as to deprive him of sleep and cause him pain.

Defence attorney David Bruck argued at a hearing of the military court on Tuesday for Judge McCall to accept the medical panel’s finding that Al-Shibh’s mental issues were too severe for him to meaningfully take part in his defence.

Mr Bruck pointed to what he said was al-Shibh’s solitary confinement over four years in detention at CIA black sites, and torture that included his being forced to stand sleepless for as long as three days at a time, naked except for a nappy and doused with cold water in air-conditioned rooms, for the man’s lasting belief that his American guards were still conspiring to deprive him of sleep.

Mr Bruck indicated at Tuesday’s hearing that al-Shibh would be expected to remain in custody while court officials waited for him to become mentally competent again – if that ever happens.

Defence attorneys and a UN-appointed investigator have argued that the five 9/11 co-defendants should be given physical and psychological care for the lasting effects of the torture they underwent while in CIA custody under the Bush administration.

Mr Bruck told Judge McCall that PTSD treatment would offer the best hope of al-Shibh ever regaining competency to stand trial.

He said the forced sidelining of the US case against the man would be “an opportunity for the country to come to account on the harm” done by what he called the CIA’s “programme of human experimentation”.

The five 9/11 defendants were variously subjected to repeated waterboarding, beatings, violent repeated searches of their rectal cavities, sleep deprivation and other abuse while at so-called CIA black sites.

The CIA says it stopped its detention and interrogation programme in 2009. A Senate investigation concluded the abuse had been ineffective in obtaining useful information.

President Joe Biden this month declined to approve post-trauma care when defence lawyers presented it as a condition in plea negotiations.