Mr. Nagin, a Democrat, was arrested in January 2013, nearly three years after he left office. He was charged with taking kickbacks in the form of cash, cross-country trips or help with the family-run granite countertop company; the bribes were handed out by men looking for city business ranging from software supplies to sidewalk repair. Many of the schemes, though not all, took place after Hurricane Katrina, when contractors crowded into the city for rebuilding work.