Gershel described finding out about the letter while the trial was taking place. He said he met with Corbett and told him to give the letter, which "on its face required disclosure," to the defense. Gershel said he didn't follow up on the order. "Frankly, when I give instructions I expect them to be followed," said Gershel, chief of the office's criminal division.

So why didn't the trial prosecutors turn them over?

Corbett said he didn't think the letter needed to be given to the defense. "In hindsight, I just wish I had given it to the defense," Corbett said. Corbett and fellow assistant U.S. attorney Richard Convertino, the lead prosecutor at trial, were replaced in September by assistant U.S. Attorney Eric Straus. Convertino said he agreed with Corbett that the letter didn't need to be turned over.

The Judge ordered the Government today to review its files and make sure there is nothing else that should have been, but wasn't, turned over.

The star witness, Youssef Hmimssa and the author of the letter, Milton "Butch" Jones, were both called as witnesses today. Hmimssa denied making the statements in the letter. Jones invoked his 5th Amendment privilege against self-incrimination. The Judge suggested the Government immunize Jones.

The letter is not the only document that the Government failed to provide the defense:

Also at issue are records of FBI interviews with a former roommate of two of the defendants. The statements raise questions about the government's assertions that Karim Koubriti and Ahmed Hannan were Islamic extremists.