911 hijacker Zacarias Moussaoui
© Sherburne County Sheriff OfficeZacarias Moussaoui
The man serving life in a federal penitentiary as the "20th hijacker" in the Sept. 11 attacks wants to testify at the 9/11 trial and has written the military judge offering his services.

"I am willing to fully testify on the 9/11 case," Zacarias Moussaoui wrote in broken English in January, "even if I was charge on the death penalty case as it incriminate me." It is handwritten and signed "Slave of Allah."

He also signs it "Enemy Combatant," which he is not. Moussaoui, 48, is a convict serving life at the SuperMax prison in Florence, Colorado. He pleaded guilty in 2005 in a federal court in Virginia to six conspiracy charges related to the 9/11 attacks.

"My take is he would like to be in the spotlight and is bored in solitary," former Moussaoui defense attorney Edward MacMahon said after reviewing a filing for the Miami Herald. " 'Slave of Allah' is how he signs all of his filings."

A review of filings on the Pentagon's war-court website shows Moussaoui has at least three times written Army Col. James L. Pohl, the judge in the Sept. 11 mass-murder case with no trial date.

The first docketed letter arrived at war-court judiciary headquarters in Alexandria, Virginia, on Nov. 12, 2015 in an envelope from the U.S. penitentiary. It had a Purple Heart postage stamp.

In that one he offers to testify about "the real 9/11 mastermind," then names Saudi Prince Turki, Princess Haifa, and a man named Omar. A lightly redacted Jan. 29, 2016 letter mentions a possible interview with an attorney for KSM — the U.S. intelligence nickname for Khalid Sheik Mohammed, accused here as the Sept. 11 plot mastermind and awaiting a death-penalty tribunal.

Moussaoui, whose recent letter offered to testify in that case, wrote Pohl last year that he wants to "expose the Saudi Royal double game with UBL," from Usama bin Laden, another U.S. intelligence acronym.

The Saudi Embassy has dismissed Moussaoui's remarks on Saudi involvement in the 9/11 plot and the French-born U.S. prisoner as a "deranged criminal."

In 2014, lawyers for a Sept. 11 victims group that is suing to hold Saudi Arabia accountable for whatever role it had in the attack interviewed Moussaoui in prison. Moussaoui mentioned that deposition in his letter to the Guantánamo judge. In it, Moussaoui describes his jihadi training, contact with bin Laden, and how in the '90s he created a database of donors to al-Qaida or the jihad. Moussaoui said the donors included prominent Saudi citizens.

He is just one of several men described as the missing "20th hijacker" in the Sept. 11, 2001 attacks that killed nearly 3,000 people in New York, at the Pentagon and in a Pennsylvania field.

One of the four passenger planes hijacked that day, United 93, had four terrorists on board instead of five, prompting belief that a 20th hijacker didn't reach the United States to fill out that terror team. Two other men who are suspected of having been assigned that role are at Guantánamo: Yemeni Ramzi bin al Shibh, awaiting the five-man, capital-conspiracy trial at which Moussaoui wants to testify, and Saudi Mohammed al Qahtani, whose torture at the U.S. Navy base in Cuba disqualified him from the 9/11 trial.

The military judge, Pohl, has apparently not confirmed receipt of the letters. In his latest correspondence, which was put on the war-court website this week, Moussaoui writes that he had written the judge but doesn't know if his mail arrived.

Moussaoui was in U.S. custody on immigration charges on Sept. 11, 2001. Employees at a Minnesota flight school had become alarmed that, although he lacked a pilot's license, he wanted to learn to fly a Boeing 747 — prompting his arrest.

Later, during his terror conspiracy court case, Moussaoui claimed that he had planned to fly a plane into the White House on Sept. 11. The federal judge at his capital case allowed a summary of testimony from Mohammed, who was held at a CIA black site at the time. Two other alleged 9/11 plotters, Walid bin Attash and Mustafa al Hawsawi, also testified through a composite statement from CIA detention.

One of his defense lawyers, Gerald Zerkin, described Moussaoui as "a compulsive letter writer" who sent perhaps 300 letters to U.S. District Court Judge Leonie Brinkema, who handled his trial.

"He liked to express his thoughts in writing," Zerkin recalled Thursday. "That took the form of pleadings sometimes. That took the form of letters sometime. And sometimes he partook of both."

In 2014, he wrote a federal judge in Florida asking to be transferred to Guantánamo, claiming he had been assaulted and harassed by other inmates and guards at the Colorado SuperMax.