Spying and gathering intelligence overseas often require deception. In contrast, testifying under oath in federal court requires telling the truth, the whole truth, and nothing but the truth.

But sometimes there are exceptions.

This week at the federal trial of suspected Al Qaeda recruit Jose Padilla, a covert agent of the Central Intelligence Agency took the witness stand. He told the jury his name was Tom Langston, but it isn't. And no one informed the jury that he was testifying under a pseudonym.

In addition, it appears that Mr. Padilla's lawyers don't know the key witness's real name at the CIA's request.

Withholding information from a defendant and his counsel at trial is unusual in American courts, although not unprecedented. But it could raise a potential issue for appellate court judges to decide whether Padilla's Sixth Amendment right to confront witnesses against him has been violated.

To some legal analysts, the episode highlights a danger that the criminal justice system is straining to accommodate the Bush administration's war on terror in ways that threaten to undermine traditional civil liberties.

But others say it appears that US District Judge Marcia Cooke, a Bush nominee confirmed in 2004, is making a conscientious effort to balance fair-trial protections against the potential national-security implications of the Padilla trial.

Although the CIA agent has testified in open court this week, it is difficult for the public and the press to understand the full context of the courtroom encounter. Rulings on the subject by Judge Cooke are under seal in the secret portion of the Padilla trial docket.

But the agent's appearance in court closely tracks a series of CIA requests to the judge. Because the true identity of the agent is classified as "secret," CIA officials asked that he be able to testify using an alias, wearing a "light disguise," and that he be permitted to enter the courtroom through a secure nonpublic entrance. In addition, the CIA asked that the agent's real name not be disclosed to the defendants or defense counsel.

"Allowing [the CIA agent] to use a pseudonym is pretty uncontroversial, especially if it is someone who is an undercover agent," says Robert Chesney, a national-security law specialist and professor at Wake Forest School of Law. "The harder question is why is it OK for the defendants to be limited in their ability to impeach [the CIA agent's] credibility because they don't really know who the guy is."

Witness names withheld before

In a public filing to the judge, prosecutors cited a series of cases withholding a witness's true name. Some involved Mafia trials and individuals in the witness-protection program. Others involved intelligence agents.

In one case, a US marine was convicted of passing classified information to a Soviet agent. A US intelligence agent testified under a pseudonym and his real name was never disclosed to the defense. That case was a court-martial rather than a jury trial in federal court.

Last year, for a pretrial hearing, two Israeli agents were permitted to testify using pseudonyms. And in 2005, Saudi intelligence officers offered videoconferenced testimony under pseudonyms, also in a pretrial hearing.

In 2004, a federal judge in Illinois permitted a former Iraqi intelligence officer to testify in a federal court trial using an assumed name.

"It seems the government is getting pretty much all they asked for," says Carl Tobias, a professor at the University of Richmond School of Law.

In the Padilla case, the CIA agent's testimony is important because it relates to a key piece of evidence: a five-page "Mujahideen Data Form" Padilla allegedly filled out before he reportedly attended an Al Qaeda training camp in Afghanistan.

Page: 1 | 2