GUANTANAMO BAY U.S. NAVAL BASE, Cuba (Reuters) - Lawyers for five alleged 9/11 conspirators who claim they were tortured in secret CIA prisons have asked a U.S. military judge to order that the prisons be preserved as evidence.

The issue is one of more than two dozen on the docket for a week of pretrial hearings set to begin on Monday in the war crimes tribunal at the Guantanamo Bay U.S. Naval Base in Cuba.

The defendants include Khalid Sheikh Mohammed, the accused mastermind of the hijacked plane attacks that killed 2,976 people on September 11, 2001, and four other prisoners accused of training and aiding the hijackers.

Defense lawyers also asked the judge to order the U.S. government to turn over all White House or Justice Department documents authorizing the CIA to move suspected al Qaeda captives across borders without judicial review and to hold and interrogate them in secret prisons after the September 11 attacks.

President George W. Bush announced in 2006 that the 9/11 defendants were among a group of "high-value" captives sent to Guantanamo from the secret prisons.

The CIA has acknowledged that Mohammed was subjected to the simulated drowning technique known as waterboarding, and the defendants said they were also subjected to sleep deprivation, threats, and being chained in painful positions.

The defense lawyers will argue that their clients' treatment was illegal pretrial punishment and constituted "outrageous government misconduct" that could justify dismissal of the charges, or at least spare the defendants from execution if convicted.

"By its nature, torture affects the admissibility of evidence, the credibility of witnesses the appropriateness of punishment and the legitimacy of the prosecution itself," the defense lawyers wrote in court documents.

At least one potential witness was also held in the CIA prisons and his treatment could raise questions about the admissibility of his testimony, said James Connell, defense attorney for Mohammed's nephew, defendant Ali Abdul-Aziz Ali.

The chief prosecutor, Brigadier General Mark Martins, said the prosecution does not plan to introduce any evidence obtained from the defendants or anyone else via torture, cruelty or inhuman treatment - which is prohibited by U.S. law and international treaty.

ABU GHRAIB PRISON

The judge presiding over the 9/11 trial, Army Colonel James Pohl, ordered in 2004 that the Abu Ghraib prison in Iraq be preserved as a "crime scene." He was at the time presiding over the trial of U.S. military police officers accused of torturing and photographing prisoners at Abu Ghraib.

Iraq was then under U.S. occupation. It was unclear whether Pohl had authority to order the preservation of the CIA prisons, whose location the government has kept secret, arguing that disclosure could threaten U.S. national security and put allies at risk.

Polish prosecutors are investigating allegations that one of the sites was in Poland, and there is evidence the CIA set up others in Romania, Lithuania and Thailand, according to reports by the Council of Europe and the United Nations.

But before the court considers the CIA prisons, it will hear issues such as whether attorney-client communications are being improperly monitored and censored at Guantanamo and how to handle sensitive but non-classified data such as medical records.

Mohammed and his nephew are Pakistani citizens. The other defendants are Yemenis Walid bin Attash and Ramzi Binalshibh and Saudi Mustafa al Hawsawi.

They have been in U.S. custody for a decade but there are still numerous legal and evidentiary issues that must be resolved before their trial begins on charges that include murder, hijacking, terrorism and attacking civilians.

"We are inching methodically toward judgment day," Martins said.