Columbia law prof disappears from NYC subway in 1956, never to be found. Perhaps he was murdered by agents of Dominican dictator, whom he’d criticized. Alleged to be involved: a former FBI agent who worked for the dictator and was convicted (later reversed) of failing to register as an agent of a foreign government. May historian obtain the ex-agent’s grand jury records? District court: Generally, courts can authorize grand jury records’ disclosure if historically significant. D.C. Circuit (over a dissent): Not so. Grand jury secrecy is the rule, the only exceptions to which are expressly enumerated, and none provides a blanket exception for historically significant documents.