The trial of a CIA contractor accused of beating an Afghan detainee went behind closed doors Monday as prosecutors tried to prevent defense attorneys from calling CIA employees as witnesses.

Even the titles of some of the potential witnesses for the trial of David Passaro are classified and can't be discussed in open court, Assistant U.S. Attorney Jim Candelmo argued during a morning hearing.

Assistant public defender Joe Gilbert argued that prosecutors were abusing the discovery process — the sharing of information by defense and prosecution — by claiming that the information was classified. At least one of the potential witnesses has appeared on national television and been interviewed in newspapers, Gilbert said.

Click here to visit FOXNews.com's Law Center

Click here to visit FOXNews.com's Crime Center

"The government is using it in such a way to deny Mr. Passaro due process and they shouldn't be allowed to do this," Gilbert said.

After a closed session, the hearing was adjourned for lunch. It was not clear if U.S. District Judge Terrence Boyle ruled on the effort to keep CIA witnesses from testifying but he said jury selection would begin as scheduled during the afternoon.

Passaro, 40, a former Special Forces medic, is the first civilian charged with mistreating a detainee during the U.S. wars in Iraq and Afghanistan. The detainee died a few days after being attacked.

Click here to visit FOXNews.com's Iraq center

Passaro's attorneys have said they want to call former CIA director George Tenet and Attorney General Alberto Gonzales, formerly the White House counsel, as part of a "public authority defense" — namely, that Passaro was following orders.

Boyle had previously limited the defense's access to several classified documents and e-mails, including a memo from the Justice Department to the CIA that the Passaro believes described the interrogation techniques allowed by U.S. law.

The government contends soldiers saw Passaro beat detainee Abdul Wali with his hands, his feet and a flashlight in June 2003 during two days of questioning about rocket attacks on a base housing U.S. and Afghan troops. Wali later died in his cell.

Passaro isn't charged with his death but with two counts of assault with a dangerous weapon and two counts of assault resulting in serious injury. If convicted, he will face up to 40 years in prison.

The government is prosecuting Passaro under a provision of the USA Patriot Act that allows charges against U.S. citizens for crimes committed on land or facilities designated for use by the U.S. government.

Click here to visit FOXNews.com's War on Terror Center

Passaro has maintained his innocence, calling the charges a reaction by the Bush administration to the Abu Ghraib scandal, in which several soldiers have been sentenced to military prison.