Alexandria, Virginia - Prosecutors in the case of United States Taliban John Walker Lindh need not prove he killed Americans, but they must show he knowingly belonged to groups that had this deadly goal, a judge has ruled.

"The government will have to prove at trial that this conspiracy existed and that the defendant knowingly joined this conspiracy... that he knew the object of this conspiracy was to kill Americans in Afghanistan, Pakistan or in the United States," said Judge TS Ellis.

Lindh's indictment did not charge him with killing Americans, but rather with being involved in a conspiracy to kill Americans abroad.

Lindh, 21, walked into court in prison fatigues and smiled briefly at members of his family.

His dark hair was clipped short and his face clean-shaven, a sharp contrast to photographs taken when he was captured last November.

Lindh's lawyers on Monday released another image of Lindh, taken in December at the US military's Camp Rhino in Kandahar, to support their claim that he was mistreated while in custody.

"The government had said that they treated John the same as American soldiers," said Lindh attorney James Brosnahan outside the courtroom. "The picture might indicate to the casual observer that that was not the case."

Prosecutors said Lindh was not tortured, and said he got medical treatment and better sleeping conditions than his doctor.

His charge sheet includes conspiring to kill Americans, engaging in prohibited transactions with Afghanistan's deposed Taliban rulers and conspiring with and aiding the Taliban and Osama bin Laden's extremist al-Qaeda network.

When defence attorney George Harris argued Lindh was not in Afghanistan to conspire to commit acts against Americans, Ellis snapped: "What was he doing over there?", then caught himself. "You don't have to answer that. It was an inappropriate question," said the judge.

Ellis agreed Lindh's attorneys should have some access to prisoners captured in Afghanistan and held in Cuba and elsewhere. - Reuters