Updated

A federal appeals court in Richmond has ordered new arguments in the case of Sept. 11 conspirator Zacharias Moussaoui.

A three-judge panel of the 4th U.S. Circuit Court of Appeals heard Moussaoui's appeal in January. But one of those judges, Karen Williams, retired last week after being diagnosed with early onset Alzheimer's disease.

Court clerk Patricia Connor said Tuesday that Williams' retirement makes new arguments necessary.

Moussaoui is the only person to stand trial in a U.S. court in the Sept. 11 terrorist attacks. He claims in his appeal that his guilty plea was invalid because the government failed to turn over evidence that could have helped his defense. He's serving a life term.