Another defendant, Nacer Bendrer, was found “guilty beyond all reasonable doubt” of supplying the revolver and assault rifle used in the killings. Mr. Bendrer, 30, sat with his head bowed during the reading of the verdicts.

Image Mehdi Nemmouche Credit... via Agence France-Presse — Getty Images

Defense lawyers had argued the killings were part of a conspiracy and Mr. Nemmouche was set up by security officials — perhaps from Iran or Lebanon — who shot the couple because the Israelis might have been members of Mossad, Israel’s intelligence service.

Security camera video from the Jewish museum’s entrance showed a man wearing a baseball cap and armed with a revolver shoot the man and woman in the back of the head at point-blank range.

He then walked down a corridor and fired into offices at the two other victims, before pulling out an assault rifle to spray the area. It was over in 82 seconds and the killer strode away without looking back.

Mr. Nemmouche, who prosecutors claim fought alongside Islamic State extremists in Syria, was captured in France almost a week later in possession of the weapons used in the killing.