Moussaoui received a sentence of life in prison in 2006 after he pleaded guilty to helping plan the 2001 terrorist attacks at the Pentagon and the World Trade Center in New York City.
Moussaoui's lawyer, Justin Antonipillai, told a three-judge panel on the 4th U.S. Circuit Court of Appeals that the plea should be thrown out because the government did not turn over evidence that could have aided his defense. Justice Department attorney Kevin Gingras argued Moussaoui knew the evidence existed but pleaded guilty anyway.
The panel questioned both attorneys for 90 minutes before it adjourned the hearing. It could be several weeks or months until the court rules.