Minutes before a major terrorism trial was about to begin, a federal judge barred prosecutors in Manhattan on Wednesday from using a key witness.
The government had acknowledged it learned about the witness from the defendant, Ahmed Khalfan Ghailani, while he was being interrogated while being held in a secret overseas jail run by the C.I.A.
The ruling by Judge Lewis A. Kaplan would seem to be a setback for the Obama administration’s goal of trying former detainees in civilian courts because it would limit the kinds of evidence that prosecutors can introduce.
After releasing his decision, the judge delayed the trial’s opening until next Tuesday, giving the government time to adjust its strategy or to appeal the ruling, although it was not immediately clear if prosecutors would appeal.
“The court has not reached this conclusion lightly,” Judge Kaplan said as he read his order from the bench. “It is acutely aware of the perilous nature of the world in which we live. But the Constitution is the rock upon which our nation rests. We must follow it not only when it is convenient, but when fear and danger beckon in a different direction. To do less would diminish us and undermine the foundation upon which we stand.”