Colonel Pohl had said prosecutors could describe the evidence as having been acquired from “telephone calls from between April and October 2001 that were later determined to pertain to the planned attacks on Sept. 11, 2001.”

Terry McDermott, co-author of “The Hunt for KSM,” said his research found that United States satellites “randomly scooped up” calls between Mr. Mohammed and an alleged deputy, Ramzi bin al-Shibh. “The N.S.A. intercepted calls but didn’t listen to them or translate them until after 9/11,” he said. “Afterward, they went through this stuff and found out what it was.”

Mr. Trivett did not disclose how or when the F.B.I. got voice samples of the accused plotters. Mr. Connell questioned in court whether they were recorded during the years that Mr. Mohammed and the other the defendants were held in the C.I.A.’s secret prison system.