MIAMI - Critics of the war crimes tribunal at Guantanamo Bay have consistently assailed the coerced confessions that may be used as evidence against the defendants and have repeatedly charged that the prisoners' severe isolation causes mental illnesses that make them unable to aid in their own defense.

Now, the critics add, evidence has emerged to show that the government advised interrogators to destroy their notes to evade legal consequences for their actions.

As the Bush administration revs up its prosecution of suspected terrorists ahead of the November election, defense lawyers and human rights advocates are ratcheting up their criticism of the offshore justice system.

The Senate Judiciary Committee heard testimony Tuesday about the treatment of prisoners at the naval base at Guantanamo Bay, Cuba, and demands that all U.S. interrogators renounce coercive techniques.

"Cruel, inhuman and degrading treatment of prisoners under American control violates our nation's laws and values," said Sen. Dianne Feinstein, the California Democrat chairing the committee.

"It damages America's reputation in the world and serves as a recruitment tool for our enemies," she said. "Perhaps most importantly, it has also limited our ability to obtain reliable and usable intelligence to help combat the war on terror, prevent additional threats and bring to justice those who have sought to harm our country."

Feinstein and the federal lawyers and agents who addressed the committee called for the shutdown of Guantanamo and the transfer of suspects' trials to U.S. federal courts.

The renewed condemnation of coercive interrogation techniques followed the revelation this week that the Pentagon had advised federal agents to destroy any written records of their attempts to exact confessions or intelligence from terrorism suspects.

Lt. Cmdr. William C. Kuebler, the Navy lawyer defending young Canadian prisoner Omar Khadr, encountered the directive in an unclassified portion of the 2003 Guantanamo "standard operating procedures" manual that was in effect at the time Khadr was interrogated at the naval base.

Because the mission "has legal and political issues that may lead to interrogators being called to testify, keeping the number of documents with interrogation information to a minimum can minimize certain legal issues," the manual notes.

Kuebler said the absence of written records of Khadr's interrogations at Guantanamo and at Bagram Air Base in Afghanistan -- where he was taken after his capture in July 2002 -- deprives him of a basis for contesting alleged confessions. He said he would file a motion to dismiss murder and terror conspiracy charges against his client.

Navy Cmdr. Pauline A. Storum, a Guantanamo spokeswoman, said it would be inappropriate to comment on documents that are now the subject of litigation.

The judge hearing Khadr's case for the last year, Army Col. Peter E. Brownback III, was dismissed two weeks ago. Though the tribunal's chief judge said the departure was the result of Brownback's plan to leave active duty in June, some observers connect his replacement with his refusal to set a trial date until the prosecution produced documents sought by the defense, including the interrogation notes.

Meanwhile, the group Human Rights Watch issued an appeal to the Pentagon on Tuesday to improve detention conditions for the 270 suspected terrorists still at Guantanamo, contending that most are held in facilities akin to the highest-security "supermax" prisons in the United States even though none have been convicted of crimes.

Noting that many of the prisoners are likely to be released -- like 500 others once detained at Guantanamo -- counter-terrorism counsel Jennifer Daskal called it "unwise and shortsighted to house them in conditions that likely have damaging psychological effects and will only breed hatred and resentment of the United States over the long term."

The government claims that the detentions and planned trials are fair and humane.

The Supreme Court is expected to rule this month on whether Guantanamo prisoners can challenge their detention in federal civilian courts. The high court's ruling could determine whether the tribunal takes up its first trial before the presidential election or the process is derailed for a third time since President Bush enacted the military commissions in November 2001.

At a hearing last month before Feinstein's committee, Defense Secretary Robert M. Gates said the United States was "stuck" with the Guantanamo prison and tribunal because there were no acceptable alternatives.

About 70 prisoners have been cleared for release, but their home countries either won't take them or haven't given reliable assurances that the men won't be mistreated.

As many as 80 may face war crimes charges, but only 19 have been identified for prosecution so far.

The remainder fall into a legal no man's land in which there is little or no evidence against them, but they are suspected of posing a danger to U.S. security if released.

carol.williams@latimes.com

© 2008 The Los Angeles Times