More recently, a federal judge in Portland, Ore., agreed to nearly identical security measures in the 2013 trial of Mohamed Osman Mohamud, who was accused of plotting to detonate a car bomb at a crowded holiday tree-lighting ceremony. That case also involved an undercover FBI agent who posed as a terrorist and helped Mohamud in the planning of the attack. The agent testified in disguise and away from public view. Mohamud was convicted and sentenced last week to 30 years in prison.