Stopping terrorism has become one of the most important missions for law enforcement these days. To help that effort, law enforcement agencies depend on informants who are trusted by the would-be perpetrator. The FBI, alone, relies on more than 15 thousand informants. But those informants can be unreliable people with conflicting motives or criminal records. Author Trevor Aaronson wrote about one such case where the FBI relied on a convicted child molester and what happened when the FBI didn’t need him anymore.