GUANTANAMO BAY NAVY BASE, Cuba -- A defense lawyer lets slip at the war court convening here that a battlefield commander changed an Afghanistan firefight report in a way that seemed to help a U.S. government murder case. Reporters hear the field commander's name but are forbidden to report it.

In another case, a judge approves the release of a captive's interrogation video showing the blurred face of an American agent. But a federal prosecutor on loan to the Pentagon withholds it ``out of an abundance of caution.''

Even as the U.S. government edges toward full-blown, war-crimes trials by military commission here, with more hearings next week, all sides are grappling with what information can be made public and what must be kept secret.

Consider: A new courtroom here sequesters Pentagon-approved spectators behind a soundproofed window. If a terror suspect tries to shout about his treatment in U.S. custody, a military censor can mute the audio feed that observers hear.

Under rules that protect interrogation techniques, the Pentagon's war court won't let the reputed 9/11 architect, Khalid Sheik Mohammed, say he was waterboarded -- something the CIA director, Air Force Gen. Michael V. Hayden, confirmed on Feb. 5.

Pentagon officials defend the Military Commissions as engaged in a delicate balancing act -- working to mete out justice to war-on-terrorism captives without exposing U.S. intelligence tactics and personnel to public scrutiny.

As long as there is an al Qaeda, they argue, such information could be used to hurt Americans or their allies.

At the same time, the commissions architects have long pledged that they will be open to international scrutiny.

''We can't disclose classified information. We can't disclose privacy information,'' the war-court legal advisor, Brig. Gen. Thomas Hartmann, said in an interview.

Unlike in federal courts, jurors at commissions are U.S. officers. In some circumstances, they can see or hear evidence that is shielded from the public.

Hartmann argues that a commissions defendant gets the same rights as a soldier at a court-martial -- among them an American military lawyer to defend him, and a presumption of innocence.

Attorneys for the Guantánamo captives disagree. They argue that, unlike civilian or military justice systems, the rules favor the government and permit evidence gleaned from abusive interrogations.

The Pentagon prosecutor has accused six of the 280 or so captives here of being 9/11 conspirators. If Hartmann's boss approves the death-penalty charges, conviction could end in their execution.

ACLU SUES

Meantime, the American Civil Liberties Union is suing the Bush administration in federal court to unseal portions of transcripts from military hearings, in which Mohammed and others now held at Guantánamo lay out allegations of torture.

'There is no remotely legitimate basis for the government to withhold these prisoners' account of their mistreatment,'' says Ben Wizner, an ACLU staff attorney and sometime war-court observer.

''I would simply note that governments don't censor information to conceal lies,'' Wizner said. ``They censor information to conceal the truth.''

The military says these trials -- the first war-crimes tribunals since World War II -- are unprecedented because they risk talking about tactics while the nation is at war. Hence, the need for secrecy.

`VAMPIRES'