A judge has rejected a request by Zacarias Moussaoui to change his guilty plea after a jury sentenced him to life in prison over the 9/11 attacks.
Moussaoui says he now wants to show his innocence
He said on Monday that seeing a US jury at work had convinced him it could operate fairly, and that he now wanted to prove his innocence.
The judge summarily rejected the motion because it was filed after sentencing.
A confessed al-Qaeda conspirator, Moussaoui was sentenced last week after a lengthy and emotional trial.
I now see that it is possible that I can receive a fair trial even with Americans as jurors
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His defence attorneys said in a footnote to their motion for Moussaoui to withdraw his guilty plea that they were aware that federal law "prohibits a defendant from withdrawing a guilty plea after imposition of sentence".
"His motion is too late and must be denied on this basis alone," Judge Leonie Brinkema replied within hours of his request.
She gave him 10 days to appeal against her decision.