On the night of the attacks, armed men overran the diplomatic compound and set fire to it. Ambassador J. Christopher Stevens and another State Department employee, Sean Smith, were killed. Hours later, militants attacked the nearby C.I.A. base with mortars and small-arms fire. Two C.I.A. security contractors, Tyrone S. Woods and Glen A. Doherty, were killed, and others were wounded.

The unusual circumstances of the crime and the evidence — an orchestrated, military-style assault in a near-failed state — were a challenge for federal investigators and prosecutors. The government showed the jury large amounts of surveillance video from the attacks, but Mr. Khattala did not show up inside the diplomatic compound until the fighting was over.

Prosecutors acknowledged that there was no evidence that Mr. Khattala had personally fired any shots or set any fires, but argued that he had nevertheless helped orchestrate the attacks and aided them while they were underway. To make that case, they drew primarily on testimony from three Libyan witnesses and on a database said to be Mr. Khattala’s cellphone records, which it had obtained from Libya.


Ahmed Abu Khattala

The government argued to the jury that several of the main attackers worked for Mr. Khattala in his militia — the prosecutor, Michael DiLorenzo, called them part of his “hit squad” in closing arguments last week — and pointed to phone records showing…

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