Washington — A Libyan militant accused of being a ringleader of the 2012 Benghazi attacks on U.S. facilities was convicted on terrorism charges on Tuesday in the assaults that killed U.S. ambassador Christopher Stevens and three other Americans. But the jury declined to find the militant directly responsible for any of the deaths of Americans.

The case was seen as a test of detention and interrogation policies developed under the Obama administration to capture terror suspects overseas for criminal trial, with the outcome likely to figure into decisions about whether to use civilian courts for such terrorism prosecutions.

The jury in Washington, D.C., deliberated for five days after a seven-week trial. They convicted Ahmed Abu Khattala, 46, in the attack the night of Sept. 11 at a U.S. diplomatic mission that killed Stevens and State Department employee Sean Smith in a fire, and in a second attack that took place before dawn on Sept. 12 on a nearby CIA annex, where CIA contractors Tyrone S. Woods and Glen Doherty were killed by mortar strikes.

The jury acquitted Abu Khattala of all but four of the 18 charges against him, finding him not guilty of the most serious charges, including murder.

Abu Khattala becomes the first person convicted in the attacks, but the mixed verdict shows the challenge of investigating and bringing these types of cases.

At trial, his defense team said Abu Khattala was drawn to the fiery scene in his hometown as a bystander. They questioned the credibility of three Libyan witnesses who testified they saw or heard Abu Khattala take steps to plan, execute or claim responsibility for the attacks.

Abu Khattala faces up to 60 years in prison, including up to 15 years in prison for each of the two terrorism counts, and up to 20 years for the destruction of property. He also faces a mandatory minimum term of 10 years for using a semiautomatic weapon in a crime of violence, to be served on top of any other sentence.