ALEXANDRIA, Va. – Zacarias Moussaoui’s behavior is abnormal even for an Al Qaeda terrorist, a defense psychologist testified yesterday.

Xavier Amador diagnosed the September 11, 2001, conspirator with paranoid schizophrenia after observing his actions and writings since 2002. He cited delusional beliefs firmly held by Moussaoui, including his conviction that President Bush will free him from prison and that his court-appointed lawyers are in a conspiracy to kill him.

He also contrasted Moussaoui’s erratic behavior with that of several other Al Qaeda terrorists who have been tried in an American criminal court.

The defense introduced affidavits filed by lawyers for Ramzi Yousef, serving life in prison for the 1993 attack on the World Trade Center, and other Al Qaeda members. All the lawyers said their clients actively assisted their defense and did not believe their lawyers were working against them.

“What we see with this individual is unique to him,” Mr. Amador said. “It’s not Al Qaeda.”

On cross-examination, prosecutor David Novak suggested that Moussaoui’s behavior is indeed consistent with other Al Qaeda terrorists. He noted that Yousef represented himself for an extended period of time and that another Al Qaeda terrorist tried to take his lawyers hostage.

Mr. Amador said he would need more information about those incidents to determine if his opinion would change.

Mr. Amador was also forced to acknowledge that he gave several media interviews about the case despite a court order barring such interviews.

Mr. Amador said his diagnosis was confirmed after an April 2005 encounter with Moussaoui in which the defendant repeatedly spit water on him – and appeared to be talking to himself.

Mr. Amador said the visit lasted for about an hour, and Moussaoui spent much of the time telling Mr. Amador to go away. Mr. Amador observed Moussaoui talking to himself in a manner that did not appear to be prayer, the witness said.

When Mr. Amador refused to go away, he said, Moussaoui spit water at him more than a dozen times, then resigned himself to Mr. Amador’s presence.

Moussaoui then complained that guards used excessive force in taking him from his Alexandria jail cell to a deposition at the federal courthouse. And he told Mr. Amador that Mr. Bush would release him from prison.

Government experts have reached conclusions that diverge from Mr. Amador’s statements, and are expected to testify later this week in rebuttal.

Moussaoui mocked the testimony about his alleged schizophrenia. He said “beautiful terrorist mind” as he was led from court during a recess, referring to the movie “A Beautiful Mind,” about a mathematician with schizophrenia.

After a second break, he said, smiling broadly, “Crazy or not crazy, that is the question.”

Mr. Amador said that Moussaoui, in his testimony, was trying to “normalize” his paranoid beliefs.

While prosecutors’ experts have been able to examine Moussaoui, he refused to cooperate with Mr. Amador or any other defense expert.

Mr. Amador based his diagnosis largely on conclusions of other mental-health professionals and an analysis of Moussaoui’s actions and writings over years. These included the numerous rambling and often insulting legal motions that Moussaoui filed during 18 months when he represented himself.