In testimony to the Senate Judiciary Committee, attorney Mark Zaid, who represents Lt. Col. Anthony Shaffer, said the Pentagon also refused to permit testimony there by a defense contractor that he also represents.
The Judiciary Committee was hearing testimony about the work of a classified unit code named "Able Danger."
Zaid, appearing on behalf of Shaffer and contractor John Smith that Able Danger, using data mining techniques, identified four of the terrorists who struck on Sept. 11, 2001 — including mastermind Mohamed Atta.
"At least one chart, and possibly more, featured a photograph of Mohamed Atta," Zaid said.
Maj. Paul Swiergosz, a Defense Department spokesman, said Wednesday that open testimony would not be appropriate.
"We have expressed our security concerns and believe it is simply not possible to discuss Able Danger in any great detail in any public forum," he said.
Swiergosz said no individuals were singled out not to testify.
"There's nothing more to say than that," Swiergosz said. "It's not possible to discuss the Able Danger program because there are security concerns."
Another Pentagon spokesman, Bryan Whitman, said later that the Defense Department would be represented at the hearing by William Dugan, the acting assistant to the secretary for intelligence oversight. Whitman also said the Pentagon believes it has provided sufficient information on Able Danger to the committees with primary oversight responsibility for the Department of Defense: the Armed Services and Intelligence committees.