WASHINGTON (AP) — A former Blackwater security contractor was sentenced Wednesday to life in prison for his role in the 2007 shooting of unarmed civilians in Iraq that left 14 people dead.

Federal judge Royce Lamberth issued the sentence after a succession of friends and relatives requested leniency for Nicholas Slatten, who was found guilty of first-degree murder by a jury in December.

Prosecutors charged that Slatten, 35, was the first to fire shots in the September 2007 massacre of Iraqi civilians at a crowded traffic circle in Baghdad. In all, 10 men, two women and two boys, ages 9 and 11,...