WASHINGTON >> The Pentagon is building a second courtroom for war crimes trials at Guantánamo Bay that will exclude the public from the chamber, the latest move toward secrecy in the nearly 20-year-old detention operation.

The new courtroom will permit two military judges to hold proceedings simultaneously starting in 2023.

On those occasions, Khalid Sheikh Mohammed and the four other men who are accused of plotting the attacks of Sept. 11, 2001, would have hearings in the existing chamber, which has a gallery for the public.

Smaller cases would be held in the new $4 million chamber. Members of the public seeking to watch those proceedings at Guantánamo would be shown a delayed video broadcast in a separate building.

It is the latest retreat from transparency in the already secretive national security cases at the base, where the military and intelligence agencies have been restricting what the public can see. That includes forbidding photography of sites that were once routinely shown to visitors to declaring both populated and emptied wartime prison facilities off-limits to reporters.

In Guantánamo’s current war court chamber, which opened in 2008, members of the public watching the proceedings live hear the audio on a 40-second delay, time enough for the judge or a security officer to mute the sound if they suspect something classified has been said.

That allowed spectators in the gallery in January 2013 to see the puzzled look of an Army judge after the CIA remotely cut off video feeds of the proceedings. Another time, only observers in the room saw guards bring an uncooperative defendant into court strapped to a restraint chair, with a soldier following behind carrying his prosthetic leg.

In 2018, guards set up a hospital bed inside the courtroom for a disabled defendant that could not be seen on video feeds.

But the new courtroom, in what is described a cost-saving measure, has no such gallery. Only people with a secret clearance, such as members of the intelligence community and specially cleared guards and lawyers, will be allowed inside the new chamber.

As a workaround, the court staff is designing a “virtual gallery with multiple camera angles simultaneously displayed,” said Ron Flesvig, a spokesperson for the Office of Military Commissions. The public would be escorted there to watch the proceedings, streamed on a 40-second delay.

During recesses in the current courtroom, lawyers and other court participants often engage with reporters and relatives of victims of terror attacks, routine contact that would be lost with the “virtual gallery.” So would the ability for a sketch artist to observe the proceedings live.

The construction plan illustrates continuing improvisation at Camp Justice, the court compound at Guantánamo, where the military has been using modular structures and tents since 2007 to avoid building more permanent structures, which require congressional approval.

The second court was designed before President Joe Biden took office with an administrationwide goal of ending detention operations at the base at Guantánamo Bay. It is being built in the United States for assembly at Guantánamo and is expected to be up and running in the middle of 2023, Flesvig said.

Meantime, workers can be seen at the court compound preparing a space adjacent to the existing courtroom for the new one. But Defense Department officials have yet to decide where to put the virtual gallery or to calculate its cost, he said.

The new court has room for just three defendants, too small for the Sept. 11 case, unless the judge severs some of the five defendants from the joint capital punishment trial.

The plan does, however, allow for a scenario of two death penalty cases being tried at the same time. In the Sept. 11 case, reporters and victims would watch live. But family members and shipmates of the 17 sailors killed in the Qaida suicide attack of the destroyer Cole off Yemen in 2000, who routinely attend sessions, would be kept away from the court with other observers, watching video feeds.

It appears to be tailor-made for the conspiracy murder trial of three men who were recently charged in two terrorist bombings in Indonesia in 2002 and 2003 that killed more than 200 people. Lawyer James R. Hodes, who represents the lead defendant, Encep Nurjaman, who is known as Hambali, said that even at the current court, access has been far from open.

Public viewing at Hambali’s arraignment in August was strictly controlled by the military, which decides which reporters, law students or human rights advocates can board a Pentagon charter plane to travel to the base. The military also controls access to two remote video sites inside the Pentagon or at Fort Meade in Maryland.

“I’ve observed trials in Mongolia that were more transparent than this,” Hodes said.

This article originally appeared in The New York Times.