Mangione's arraignment for the killing last December attracted several dozen people to the federal courthouse in Manhattan, including former Army intelligence analyst Chelsea Manning, who served about seven years in prison for stealing classified diplomatic cables.
Mangione, who has been held in a federal jail in Brooklyn since his arrest, arrived to court in a mustard-colored jail suit. He chatted with one of his lawyers, death penalty counsel Avi Moskowitz, as they wanted for the arraignment to begin.
Late Thursday night, federal prosecutors filed a required notice of their intent to seek the death penalty.