The United States concealed the existence of taped telephone calls between the alleged mastermind of the Sept. 11 attacks, Khalid Shaikh Mohammed, who spoke in code with three of his accused co-conspirators, according to the New York Times.

The tapes featuring Khalid Shaikh Mohammed and three of his accused co-conspirators were made between April and October 2001, prosecutors say. (United States Department of Justice)

The existence of the tapes was revealed by their defense attorney, Jay Connell, as part of a protest over plans for prosecutors to use them as evidence at the death penalty trial more than 17 years after 19 hijackers took four commercial airplanes by force - crashing them into the World Trade Center, the Pentagon and a Pennsylvania field, killing nearly 3,000 people according to the 9/11 Commission Report - aspects of which have been refuted by groups such as Architects & Engineers for 9/11 truth.

Defense attorneys have known of the tapes since September 30, 2016 - when prosecutors handed over audio and transcripts of the conversations, making clear that they intended to use them against the men at trial. When the defense attorneys attempted to investigate the tapes - including the method used by the government to record the calls, they hit a brick wall. The original trial judge, Army Col. James L. Poul had secretly issued an order preventing them from knowing about the call collection system - or asking questions about it.

Connell - who questioned in court whether the tapes were recorded during the years that Mohammed and the other defendants were imprisoned in the CIA's secret prison system - is now arguing that the tapes should not be allowed as evidence in the death penalty trial, as the defendants' basic right to challenge the evidence being used against them are being violated.

Mr. Connell, who is representing Mr. Mohammed’s nephew, Ammar al-Baluchi, said that prosecutors secretly obtained a ruling in August 2018 from Colonel Pohl forbidding defense lawyers from learning how the phone calls were collected or investigating that question. The phone calls in at least two languages were made between April and October 2001. Mr. Connell said the restriction on investigating the origins of the tapes violated a defendant’s basic right to challenge the evidence being used against him. He argued in court on Monday that the evidence should be suppressed or that the case should be dismissed. He said the constraints the defense faces regarding the tapes violate the Sixth Amendment, which sets out the rights of defendants in a trial. -NYT

According to the report, the military trial judges have yet to decide which aspects of the Constitution apply to military commissions - war courts established by President George W. Bush following the 9/11 attacks.

Arguing for the government, prosecutor Clayton Trivett responded that defense attorneys should be allowed to question an FBI linguist who analyzed the tapes and compared the defendants' voices to determine that they belonged to Mohammed, his nephew al-Baluchi and the two other alleged plotters. Trivett added that the defense team should be able to question the FBI analyst who decoded the conversation.

The only catch? They still don't get to know about how the calls were recorded.

The only restriction, he said, is on defense lawyers trying to investigate “how the United States government got those calls,” something prosecutors persuaded the judge would endanger national security. 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.” -NYT

The Times notes that "The Hunt For KSM" author Terry McDermott said that he found during his research that US satellites "randomly scooped up calls" between Mohammed and an alleged deputy, Ramzi bin al-Sihbh.

"The N.S.A. intercepted calls but didn’t listen to them or translate them until after 9/11," McDermott said. "Afterward, they went through this stuff and found out what it was."

Trivett denied that the voice samples were from the CIA black site prior to their transfer to Guantánamo in 2016 to stand trial.

This week, attorneys will argue in what will be the 24th round of pretrial hearings since the men were arraigned in 2012, in front of military judge Col. Keith Parrella of the Marines.