(Patrick Semansky — Associated Press)

The request was later denied.

The attorney, David E. Coombs, opened the pretrial hearing at Fort Meade, Md., by charging that Army Lt. Col. Paul Almanza, the presiding officer, cannot be perceived as impartial. The hearing is to determine whether Manning should face a court-martial.

Almanza, an Army reservist, is a career prosecutor with the U.S. Justice Department, which has an open investigation into WikiLeaks co-founder Julian Assange’s role in the leak.

“That simple fact alone, without anything else, would cause a reasonable person to say, ‘I question your impartiality,’ ” Coombs told Almanza, who works in the Justice Department’s child exploitation unit and has been with the department since 2002.

After a recess, Almanza rejected the assertions and said he would not recuse himself.

“I do not believe a reasonable person, knowing all the circumstances, would be led to the conclusion that my impartiality would be reasonably questioned,” he said. “I thus deny the defense request to recuse myself.”

Coombs then moved to file a writ with the Army Court of Criminal Appeals to stay the proceedings until a decision can be made on whether Almanza should continue to preside.

Manning, 23, is making his first public appearance since being detained in Baghdad in May 2010. He sat calmly, without expression, at the defense table, watching his attorney intently and occasionally fiddling with a pen or taking notes. His hair close-cropped, Manning wore Army fatigues and prison-issue dark-rimmed glasses. He spoke only to say that he understood his rights and the potential charges and that he approved of his defense team.

In dramatic form, Coombs, the civilian defense attorney, argued that even the mere appearance of bias dictates that Almanza should remove himself from the proceeding. He punctuated his arguments with gestures and occasionally turned to face the audience of about 50 people, including some of Manning’s relatives.

At one point, Almanza chided him for playing to the gallery. “Mr. Coombs,” he said, “who are you addressing?”

Manning faces charges of aiding the enemy, which could carry a death penalty or life in prison, as well as violating the Espionage Act by causing government intelligence to be published on the Internet, plus several lesser charges.

Coombs argued that Almanza has already shown he is partial toward the prosecution. He noted that Almanza has approved all 20 of the government’s requested witnesses, while allowing only two of the defense’s 38 requested witnesses to appear. Some of those who were rejected would have been able to testify that the national security harm caused by the leaked documents would be minimal, Coombs suggested.

Meanwhile, he complained, the government has been granted delays to determine whether the material leaked was properly classified and to assess the damage to national security and foreign relations.

“A year and a half later, this is what are we doing?” Coombs said. “Where’s the damage? Where’s the harm? That’s what the defense wanted to get at today in this hearing. Yet you again ruled today, ‘No, I’m not going to hear that.’ ”

Coombs criticized Almanza’s decision not to close a portion of the proceeding that the defense had asked be closed to avoid prejudicing the case against Manning. He also argued against allowing unsworn statements from government witnesses to be considered over the defense team’s objections.

“Any of those individually would [suggest] you recuse yourself,” Coombs said. “Collectively, they mandate it.”

At times, Coombs appeared to become the prosecutor, asking Almanza whether he “could see how a reasonable person” hearing the arguments Coombs was making would say that Almanza could not be impartial.

“No, I don’t believe I am biased,” Almanza said.

The prosecution similarly asked Almanza questions to determine whether he thought he could be fair, and whether he had followed the military rules of court martial. In all cases, he replied that he had.

Michael J. Navarre, a military law expert and former lieutenant commander in the Navy Judge Advocate General’s Corps, said it was unlikely that Coombs would prevail in his efforts to remove Almanza.

“Unless there’s facts connecting the investigating officer to the actual Manning case, the fact that he works within the overall Department of Justice is unlikely to cause him to recuse himself,” Navarre said. Similarly, he added, the convening authority, which is a military office that ultimately decides whether a case should proceed to court-martial, is unlikely to want to remove him.

David Velloney, a Regent University law professor and former Army lawyer, said Coombs appeared to be “grandstanding a bit.” He said Coombs was “attempting to telegraph to the government that it is going to be a difficult case and that they are going to call into question every move that the government makes — an attempt to garner public sympathy from those who support Manning and distrust the military.”

Protesters gathered Friday morning outside the gates of Fort Meade to show support for Manning. The group included representatives from the Bradley Manning Support Network as well as a contingent of the Occupy Wall Street group from New York and Washington, D.C.

In addition, veterans groups were holding a vigil for Manning. The Bradley Manning Support Network plans to hold a rally at Fort Meade on Saturday. It has also planned 50 demonstrations worldwide for Saturday to mark Manning’s 24th birthday.