A federal judge has ruled that a jury should decide whether two psychologists who helped design the CIA's harsh interrogation methods used in the so-called war on terror should be held accountable for the suffering.

US District Judge Justin Quackenbush refused on Friday to immediately rule in favour of the American Civil Liberties Union (ACLU), which brought the lawsuit on behalf of three former detainees and argued that the psychologists were the architects of what became the CIA's torture programme after the September 11, 2001 attacks.

The men were subjected to physical assaults and sleep deprivation, forced to stand for days in nappies with their arms chained overhead, doused with icy water and stuffed into boxes.

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Quackenbush said the evidence warrants a trial on the issues. The trial is set for September 5.

The case will move forward for the representatives of the estate of Gul Rahman, who was "starved, sleepless and freezing" before he died of hypothermia while chained in a prison cell following extended interrogation.

Quackenbush, however, said he has reservations about the evidence as it applies to the two living detainees: Suleiman Abdullah Salim and Mohamed Ahmed Ben Soud.

He said he would review the case and issue a written ruling regarding his position on the other two men.

He also granted the ACLU's request to use at the trial the Senate Intelligence Committee Study on the CIA Detention and Interrogation Program, completed in 2012 and made public in 2014.

Quackenbush closed the hearing by urging the lawyers to try to settle the case and avoid a costly trial.

He noted that the contract that psychologists James Mitchell and John Jessen had with the government indemnified them against any judgments.

The psychologists' lawyers are being paid out of a pot of money provided by taxpayers and established in an indemnity contract.

Their lawyers argued that the psychologists should not be punished for the CIA's actions.

Torture techniques 'architect'

When the CIA sought help with interrogating the agency's first prisoner, Abu Zubaydah, a high-value detainee, Mitchell provided methods, lawyer Brian Paszamant told the judge.

Simply providing a memo does not make them guilty of aiding and abetting torture, he argued.

Didn't Mitchell in his book "describe himself as the architect of the enhanced interrogation programme?" Quackenbush asked.

"What does it mean to be an architect?" Paszamant responded.

The psychologist prepared a 2002 memo for the CIA, but had no control over what happened next, he said.

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The CIA set up the prisons, chose the detainees, decided who conducted the interrogations and who was present, Paszamant said.

The psychologists designed the programme for a high-value detainee and did not know the government would use it on middle-alue and other detainees, he said.

"Everything was the absolute direct control of the US government through the CIA," another of the psychologists' lawyers, Jim Smith, said.

There were five or six people present during the Zubaydah interrogations, Smith said, but only Mitchell and Jessen are being sued.

ACLU's argument

Dror Ladin, ACLU lawyer, said the psychologists were much more involved than simply writing a memo and then stepping away.

Mitchell's vision of a successful programme involved corrosive methods designed to instill fear and despair, Landin said. They then became involved directly in the interrogation of Zubaydah, he said.

"They cut off his clothing, slammed him into walls," Ladin said. "They admitted that they kept it up for weeks. As soon as they were done with Zubaydah, they helped expand the programme."

Jessen was directly involved in six interrogations of Rahman at the secret prison called Colbalt, Ladin said.

READ MORE: The dark prisoners - Inside the CIA's torture programme

Even if they never saw or interrogated Salim or Ben Soud or any of the other detainees, they are liable under the law, Ladin said.

"International law is clear on this," he said.

"Participation may occur before, during or after the crime is committed. When one person orders torture and one provides the tools and another inflicts it, international law says all are responsible."

The two psychologists were paid $81m for their help, Ladin said.