McDermott’s co-author, Josh Meyer, secured a slot as an observer on behalf of The Medill National Security Journalism Initiative, where he now works. The last time he was there, he reported on the Bush-era efforts to prosecute Mohammed for The Los Angeles Times.

The observers will also include for the first time the Navy’s senior lawyer on 9/11 — retired Rear Adm. Donald Guter, who is being sent by the legal group Human Rights First to observe. Guter, who was at work and felt Flight 77 crash into the Pentagon that day, is no fan of the military commissions system.

“I think it should be in federal courts,” said Guter, calling the U.S. civilian system “the gold standard” of criminal justice.

Even the Obama administration’s reformed war court system, he says, is too burdened by questions of legal jurisdiction and hearsay exceptions to be credible in many human rights and international law circles.

Army Brig. Gen. Mark Martins, the Pentagon’s chief prosecutor, has urged critics to give the court a chance. “If observers will withhold judgment for a time,” he told a gathering at Harvard Law School last month, “the system they see will prove itself deserving of public confidence.”

But, Guter said in an interview this week, the alleged 9/11 perpetrators don’t deserve the dignity of a military commission.

“They’re thugs, not soldiers,” he said. “Put them through the federal system with all the real miscreants there. We’re giving them a status as real warriors by giving them commissions.”

Attorney General Eric Holder wanted to hold the trials in New York City, but Congress closed off any possibility of federal trials through legislation.

Other lawyers taking up observer seats offered by the Office of Military Commissions include Anthony Romero, executive director of the American Civil Liberties Union, which has funded some of the 9/11 defense work; former New York prosecutor and Iran-Contra investigator Ken Roth, executive director of Human Rights Watch; Amnesty International’s Tom Parker and Judicial Watch’s Lisette Garcia.

With only sporadic interest in earlier Obama-era proceedings, the 9/11 hearing puts a renewed spotlight on the expeditionary legal compound the Bush administration fast-tracked in 2008 for $12 million by requisitioning supplies from existing Defense Department inventories.

It’s built atop an abandoned airstrip on a remote corner of the base overlooking Guantánamo Bay.

Its centerpiece is a pre-fab maximum-security, state-of-the-art courtroom built inside a building that looks like a warehouse, and is surrounded by fencing topped with barbed wire and displaying signs that forbid photography. It was brought in by barge in pieces and can be dismantled and taken away.

Reporters and observers are put up in nearby tents that look like Quonset huts, with drinking water chilled in a $32,000 U.S. Air Force refrigeration container meant to ship the dead home from war. Lawyers get a nearby trailer park while senior court staff and the 9/11 victims get guest officers quarters.

The compound has been sparsely used during the Obama administration, with the tent city only filled to capacity as emergency transition housing for troops and journalists bound for Haiti after the 2010 earthquake.