The initial batch of documents retrieved by the National Archives from former President Donald J. Trump in January included more than 150 marked as classified, a number that ignited intense concern at the Justice Department and helped trigger the criminal investigation.

In declining to seek prosecution of Hillary Clinton, FBI Director James Comey said the former Secretary of State’s handling of classified emails was “extremely careless” - conduct, legal experts said, that falls short of “gross negligence,” a standard for criminal charges under the Espionage Act.