By Alex Van Wel BBC correspondent in Washington

Thursday's confusing exchange in a Virginia courtroom between Zacarias Moussaoui and federal judge Leonie Brinkema is the latest in a string of difficult moments in this case.

When he takes an action on Wednesday, he may well forget what it is that he did on Monday

Moussaoui's former lawyer Frank Dunham

Mr Moussaoui is the only person charged with direct involvement in the attacks on America last year and he has chosen to handle his own defence.

But many, including his court-appointed lawyer, do not believe he is competent to do so.

The trial of Mr Moussaoui was always going to be a dramatic affair.

But since the sentencing deal last week in the case of John Walker Lindh - the so-called American Taleban - Mr Moussaoui's case has taken on an even greater significance.

'Against protocol'

The problem for the court has been his insistence that he represents himself.

Moussaoui faces charges of conspiracy to commit terrorism

It has meant that each hearing has been characterised by Mr Moussaoui's tendency to go against legal protocol.

In total he has filed more than 70 motions, many of which are impossible to understand.

Frank Dunham - the lawyer assigned to Mr Moussaoui by the court - spent many hours with him before being accused of being part of a conspiracy against him and unceremoniously sacked.

"When he takes an action on Wednesday, he may well forget what it is that he did on Monday," Mr Dunham said.

"He files these repetitive motions on the same topic... Four or five times the judge will have to consider something and then say "well, it's denied and, by the way, I denied it last week"."

Serious charges

This latest hearing was called formally to indict Mr Moussaoui on a revised charge. The prosecution believes the revision will improve its chances of securing a death sentence against Mr Moussaoui.

If the judge decides to accept his guilty plea, it will mean there will be no trial and the case will move immediately to sentencing.

But that is unlikely to happen unless she is convinced Mr Moussaoui understands and accepts all six counts of conspiracy to commit terrorism against him.

Ms Brinkema has always kept open the possibility of bringing Mr Dunham back in.

When the court meets again in a week, it is possible that is precisely what she will do.