The trial of Zacarias Moussaoui has provided opportunities for followers in the courtroom to discuss which moment in the regularly odd proceeding is the oddest. The prize-winning occasion may have occurred when Mr. Moussaoui took the stand for the second time last week.

He quickly became embroiled in an argument with Gerald T. Zerkin, one of his court-appointed lawyers, who, despite Mr. Moussaoui's skepticism, is trying to prevent the Justice Department from executing him. The bizarre moment: the chief prosecutor, Robert A. Spencer, who is without doubt trying to have Mr. Moussaoui executed, rose to Mr. Moussaoui's defense, objecting that Mr. Zerkin was badgering the witness.

Of course, the upside-down nature of Mr. Moussaoui's status as a witness exists because Mr. Zerkin and his team are eager to demonstrate that Mr. Moussaoui is mentally unstable, and they are content to have an argument with him that may demonstrate that to the jury.

Mr. Spencer, on the other hand, is reluctant to have the jury — which will soon decide whether to order Mr. Moussaoui's execution — be shown signs that Mr. Moussaoui may not think in a logical manner.

Judge Leonie M. Brinkema has presided over the trial, now in its seventh week, with the tolerant air of a veteran high school teacher trying to maintain order in the pre-law club.