A New York prosecutor who helped draft an exhaustive report on the Sept. 11 attacks (search) testified Monday at the retrial of a Moroccan accused of aiding the Hamburg-based suicide hijackers, including Mohamed Atta (search).

The Hamburg court hoped that Dietrich Snell, a U.S. deputy attorney general, might shed more light on the role of defendant Mounir el Motassadeq (search).

Snell was involved in the Sept. 11 Commission report for the U.S. Congress, which found the pilots were recruited by Khalid Shaikh Mohammed, an Al Qaeda (search) leader in U.S. custody who allegedly masterminded the 2001 attacks on New York and Washington.

Introducing Snell as a witness, Judge Ernst-Rainer Schudt said his main aim was to find out more about the interrogations of Mohammed and other Al Qaeda leaders. The court has received summaries of the questioning of Binalshibh and Mohammed, but has repeatedly asked the United States for more details.

El Motassadeq, 30, is being retried on more than 3,000 counts of accessory to murder and membership in a terrorist organization on charges he provided logistical support for suicide pilots Atta, Marwan al-Shehhi and Ziad Jarrah.

He was convicted in 2003 on those charges and sentenced to the maximum 15 years.

But an appeals court threw out the conviction last year, ruling he was unfairly denied testimony by key Al Qaeda suspects in U.S. custody, including Khalid Shaikh Mohamed and the Hamburg cell's suspected contact with Osama bin Laden's organization, Ramzi Binalshibh.

Binalshibh was arrested on the first anniversary of the Sept. 11 attacks in Pakistan and is now in secret U.S. custody.

The Sept. 11 Commission report includes a section on "The Hamburg Contingent" in which el Motassadeq is identified as an "associate" who helped conceal a 1999 trip to Afghanistan by the three future suicide hijackers and Binalshibh.

"While the four core Hamburg cell members were in Afghanistan, their associates back in Hamburg handled their affairs so that their trip could be kept secret," the report said. "Motassadeq appears to have done the most."

It was unclear how much new insight Snell would be able to add, as the section in the report is largely based on testimony heard in el Motassadeq's first trial and at the trial of his friend and fellow Moroccan Abdelghani Mzoudi, who was tried of the same charges and acquitted February last year.

Snell has told the court in a letter he is not authorized to discuss material that the United States considers secret intelligence.