Abu Khattala was photographed shortly after his apprehension by U.S. special forces near a villa south of Benghazi, Libya, during the evening of June 15, 2014. (U.S. Attorney's Office for the District)

Ahmed Abu Khattala insisted he was only a bystander as the gunfire crackled and then exploded after sundown five years ago in Benghazi, Libya.

Starting Monday, he stands trial in Washington for conspiring to kill four Americans as the accused ringleader of the lethal, nighttime assaults on U.S. diplomatic and intelligence facilities on Sept. 11 and 12, 2012.

Abu Khattala, a 46-year-old Libyan who was a leader in an extremist anti-Western militia, is the only person to face trial in the United States for the attack. U.S. Ambassador J. Christopher Stevens was among its victims.

In announcing that Abu Khattala had been captured during a secret nighttime raid by U.S. commandos in June 2014, then-President Barack Obama said efforts to bring those responsible for the attack were continuing but “with this operation, the United States has once again demonstrated that we will do whatever it takes to see that justice is done when people harm Americans.”

File photo of the USS New York in the Hudson River. Abu Khattala was interrogated by a U.S intelligence team onboard after which law enforcement investigators with the FBI questioned him. (U.S. Attorney's Office for the District)

Abu Khattala has pleaded not guilty to 18 counts, including conspiracy, murder and material support of terrorists in the deaths of Stevens, State Department communications expert Sean Patrick Smith and security contractors Tyrone S. Woods and Glen Doherty.

He faces up to life in prison if convicted in federal court.

In repeated interviews with Western journalists in Benghazi, where he lived openly before his capture, Abu Khattala, a former auto mechanic and political prisoner of Libyan dictator Moammar Gaddafi, denied involvement in the attacks but gave contradictory explanations of his role and voiced varying degrees of approval of it.

A jury of 12, plus three alternates, was selected in September to hear the first major terrorism trial in the United States since 2015, and the first in the nation’s capital involving an alleged Islamic extremist strike since the Sept. 11, 2001, attacks. The jurors — nine women and six men, all from the District — include a preschool teacher, a retired FBI information technology worker, an English professor, a stamp designer and a manager at a landscape design firm. The trial is anticipated to last four to six weeks.

Prosecutors are expected to call dozens of witnesses, including relatives of victims, U.S. security personnel involved in rescue operations on the ground, and multiple Libyan nationals and eyewitnesses who will testify against Abu Khattala using pseudonyms for their and their families’ safety.

In sealed proceedings before the trial’s start, both sides have winnowed down tens of thousands of pages of classified information for use in open court, including records of telephone calls prosecutors allege Abu Khattala placed from the scene at the time of the assault.

Testimony is expected to elicit the first public statements from witnesses whose views have been summarized by congressional investigators, a State Department review board and in a 2016 feature film based on a book written with the participation of security teammates of Woods and Doherty.

The trial will return a focus to the criminal prosecution of a five-year-old attack that created an enduring diplomatic and political minefield for Obama and his secretary of state, Hillary Clinton, that extended through the 2016 presidential election.

Obama approved Abu Khattala’s capture by U.S. Special Operations forces, holding it out as a model of how to try terrorist suspects in civilian courts despite objections of Republicans in Congress, including Jeff Sessions, then a senator from Alabama and now the U.S. attorney general.

Before joining the Trump administration to head the Justice Department, Sessions argued that terrorism suspects should be detained at Guantanamo Bay and prosecuted by military tribunals.

The Libyan government also had protested Abu Khattala’s capture as a violation of Libyan sovereignty, inflaming tensions in that country’s bloody civil war after the U.S.-backed overthrow of Gaddafi.

And during her presidential run, Clinton confronted partisan critics who asserted her actions as secretary impeded rescue operations. She emphatically denied that, and several investigations debunked the allegations. But one of those investigations into the attacks disclosed that Clinton had used a private email address and server as secretary of state, an issue that followed her through the campaign.

Abu Khattala’s prosecution has already yielded a significant national security legal ruling for U.S. authorities, preserving their flexibility in blending civilian and military options to interrogate militants seized overseas in irregular operations.

U.S. District Judge Christopher R. “Casey” Cooper, who is presiding over the trial, in August denied a motion by Abu Khattala’s attorneys to suppress statements he made to FBI agents after his capture.

Cooper’s 59-page opinion marked one of the first and most detailed U.S. court decisions upholding the constitutionality of the two-step, ship-based interrogation policy developed in recent years to extract actionable intelligence while shielding the ability to use federal courts to prosecute high-value terrorism suspects captured overseas.

Abu Khattala was questioned during a 13-day transatlantic voyage in a specially constructed brig below deck of the USS New York. He first faced an intelligence-gathering team and later a separate “clean team” of FBI agents who collected evidence for the civilian trial after reading Abu Khattala his Miranda rights to remain silent and have a defense lawyer.

Abu Khattala waived those constitutional protections, previous case filings show, and Cooper’s ruling allowed what he said to agents to be used in court.

Abu Khattala was charged in a sealed complaint in July 2013, and indicted in June and October 2014 with additional charges.

The U.S. government in January 2014 designated Abu Khattala a terrorist and Ansar al-Sharia, a militia that seeks to establish sharia law in Libya, a terrorist organization. The government alleges the Benghazi attacks were carried out by Libyan-based extremists, including members of Ansar al-Sharia and an extremist brigade known as Ubaydah ibn al Jarrah that Abu Khatalla commanded.

In court papers, U.S. authorities assert Abu Khattala told others he believed the American diplomatic presence in Benghazi was cover for a U.S. intelligence-gathering facility and vowed to “do something about this facility.”

Abu Khattala drove with attackers to the diplomatic post and participated in “coordinating the efforts of his conspirators and turning away emergency responders,” prosecutors allege.

Stevens and Smith died of smoke inhalation after attackers set ablaze a villa containing a “safe room” at the compound late on Sept. 11, 2012.

As midnight neared, Abu Khattala allegedly showed up on internal security cameras, entered a mission office and oversaw the looting of data about a nearby CIA annex that soon came under mortar fire, killing Woods and Doherty.

Last year, Jeffrey D. Robinson, an attorney for Abu Khattala, said in court that “everyone agrees what happened in September 2012 was a tragedy and Americans suffered a tragic loss.” He added: “Mr. Abu Khattala agrees it was a tragic loss but disagrees he is the person responsible for it.”

The defense team telegraphed one of its likely arguments about Abu Khattala’s culpability in Question 99 of a 130-question form for prospective jurors that asked their view of the fact that although multiple individuals were involved in the attacks, Abu Khattala is the only one to face trial.

The case is a rarity as he readies for a full civilian trial.

Another Libyan seized in Tripoli and detained aboard a ship, Nazih Abdul-Hamed al-Ruqai, also known as Anas al-
Libi, died of liver cancer days before his trial was set to start in New York City in January 2015. He was accused of involvement in the 1998 al-Qaeda bombings of two U.S. embassies in East Africa.

A Somali named Ahmed Abdulkadir Warsame pleaded guilty in 2011 to terrorism charges, avoiding a trial, after being captured in the Gulf of Aden by the U.S. military and held at sea for two months. He was charged with providing material support to the Islamist militant groups al-Shabab and al-Qaeda in the Arabian Peninsula.