It’s understandable if the American public has forgotten that a man who nearly assassinated a U.S. president walks freely among them; after all, it seems too unbelievable to be true. But John Hinckley Jr. — the man who put a bullet within an inch of President Ronald Reagan’s heart, who severely wounded and cut short the life of James Brady and who shot Secret Service agent Tim McCarthy and police officer Thomas Delahanty in March of 1981 — has more freedom than many men who have merely plotted such evil. Beginning with the mind-boggling verdict he received (not guilty by...