A man waves his rifle as buildings and cars are engulfed in flames inside the U.S. compound in Benghazi, Libya, late on Sept. 11, 2012. (AFP/Getty Images)

A Libyan militant charged with leading the lethal 2012 attacks on a U.S. diplomatic compound in Benghazi will ask a federal judge to throw out his statements to American authorities during his overseas capture and interrogation for 13 days aboard a U.S. Navy vessel.

The move to toss Ahmed Abu Khattala’s statements was disclosed in a court filing late Monday as U.S. prosecutors and his defense prepare to argue the question using live testimony this month from 16 witnesses, including an onboard doctor and FBI interrogators, in the run-up to a September trial.

Abu Khattala’s request renewed a challenge to evidence gleaned through hybrid military-civilian policies adopted by U.S. officials to wring intelligence from terrorism suspects while preserving the ability to try them in civilian courts.

Abu Khattala, 45, pleaded not guilty last fall to charges including murder, conspiracy and destroying a U.S. facility in the Sept. 11, 2012, attacks that killed U.S. Ambassador J. Christopher Stevens and three other Americans.

He was questioned by U.S. military, intelligence and law enforcement officials shortly after his June 2014 capture by U.S. Special Operations forces, his attorneys have said. He was interrogated again by a second FBI team aboard the USS New York, at which point he allegedly waived his right to not answer questions.

In pleadings in Washington before U.S. District Judge Christopher R. Cooper of the District, Abu Khattala’s lawyers with the federal public defender’s office of the District and the Lewis Baach law firm challenged whether the defendant was able to exercise his constitutional right against self-incrimination while in military custody and being transported to the United States.

At a two-week hearing set to begin May 10, Abu Khattala’s lawyers said, they planned to call Hawthorne Smith, a clinical psychiatrist and associate professor at New York University School of Medicine, to testify to the “effects of the defendant’s long first-hand exposure to torture and extreme human rights abuses in Libya, including whether he would have been capable of providing a knowing waiver of his right to an attorney.”

Prosecutors with the national security section of the U.S. Attorney’s Office for the District consented to Smith’s testimony at the May hearing but reserved their right to challenge his testimony at trial, according to the new filings.

Those filings show that the government expects to call 14 witnesses at this month’s hearing, including the captain of the USS New York; five FBI officials, including agents who interviewed Abu Khattala, were present when he was apprehended or were onboard; a physician who attended to him; and senior State and Justice department officials.

On Sept. 13, 2012, a Libyan man investigates the inside of the U.S. compound in Benghazi after an attack that killed four Americans, including Ambassador J. Christopher Stevens. (Mohammad Hannon/AP)

Monday’s court filing acknowledged the mostly secret nature of the government’s case to this point but also revealed a previously undisclosed court order from Cooper in April that said some of the May hearing would be held out of public view to protect classified information.

Abu Khattala was charged by sealed complaint in July 2013 in the deaths at Benghazi. The U.S. government in January 2014 designated Abu Khattala a terrorist and Ansar al-Sharia, an armed militia he led that seeks to establish sharia law in Libya, a terrorist organization that allegedly carried out the attacks.

In June 2014, Abu Khattala was lured to a villa south of Benghazi and captured in a secret raid, coinciding with his formal indictment. He was held in military custody and interrogated for five days by a High-Value Detainee Interrogation Group, according to his attorneys, who contend that information from such efforts may further intelligence-gathering but cannot be admitted as evidence.

After that, a second group of FBI agents told Abu Khattala that he was under arrest and read him his Miranda rights, according to U.S. officials and defense filings.

His defense lawyers say that Abu Khattala asked for a lawyer, that the government did not have one available and that FBI agents interrogated him for seven more days.

The government says Abu Khattala never invoked his right to remain silent or his right to counsel.

Both sides have agreed that two members of the intelligence team will testify in a closed part of the May 10 proceeding. The onboard physician will testify in public, but the doctor and one of the intelligence team members will be identified using aliases for their safety, both sides agreed.

The government has agreed to declassify some material sought by Abu Khattala’s defense attorneys, but other still-classified information will be presented under a “silent document rule,” which allows it to be admitted into evidence and known to the parties, a witness and the judge while not being discussed in open court.

Abu Khattala’s lawyers earlier failed in an attempt to dismiss most of the 18-count indictment against him, urging the federal courts not to legitimize what they called the “well-planned lawlessness . . . [of his] arrest, abduction and interrogation.”

Cooper denied their requests in February 2016 but said if there were such a violation, the proper remedy would be to exclude unconstitutionally obtained evidence, something this month’s hearing will decide.

The upcoming hearing returns the spotlight to attacks that became a partisan lightning rod during last year’s presidential election, raised in debates and dramatized in a feature film released nationwide in early 2016.

While running as a Democratic candidate, Hillary Clinton, secretary of state at the time of the attacks, repeated her categorical denials of the long-debunked charge that she impeded rescue attempts, while acknowledging State Department findings that security was inadequate for Benghazi.