WASHINGTON (CNN) — A judge has appointed a psychiatrist to perform a competency evaluation of terror suspect Zacarias Moussaoui.

The examination is to help the court to decide how to proceed on Moussaoui's request to fire his current lawyers and either defend himself or have the court find a Muslim attorney for him.

U.S. District Judge Leonie Brinkema chose psychiatrist Dr. Raymond Patterson to do the evaluation of Moussaoui, accused of being part of a conspiracy against the United States involving al Qaeda and its leader, Osama bin Laden. Prosecutors believe Moussaoui may have been trained at one of bin Laden's terrorist camps.

In an order appointing the psychiatrist, Brinkema said she must decide whether Moussaoui is competent to waive counsel or "whether the decision is the product of a mental disease or defect rendering the decision involuntary or without a knowing appreciation of its consequences."

Among six mental-health experts proposed for the evaluation, Patterson "appears to have the most experience with multi-cultural issues in the forensic psychiatry field," Brinkema said in the order. "We find this experience makes him particularly valuable to this case."

Moussaoui's current attorneys have argued the suspect should undergo a broad exam, including any government documents that may indicate his mental capacity. Government prosecutors had wanted a more narrow review.

Brinkema said she would not specify guidelines for Patterson to follow. It is up to him who he interviews and what documents he reviews, said Brinkema. The report is due in 30 days.

The judge also ruled that prosecutors or people working for them cannot have contact with Moussaoui unless one of his lawyers is present or if the court allows it. Moussaoui last week made an attempt to reach government prosecutors to talk about classified material.

Patterson, a Washington psychiatrist, testified in the trial of Francisco Martin Duran, charged in the 1995 attempted assassination of President Clinton, and served from 1983 to 1987 as the psychiatrist for the family of John Hinckley, incarcerated at St. Elizabeth's mental hospital after the shooting of President Reagan.