Former FBI chief James Comey wrote Sunday that "the FBI is up for this" because it is "full" of "people who just want to figure out what's true." 

But truth has often been a scarce commodity in FBI investigations. Consider these cases stretching back decades:

?The chief of the FBI's violent crimes section was sent to prison in 1997 for destroying a report criticizing FBI conduct in a 1992 showdown at Ruby Ridge, Idaho. A federal judge lambasted the FBI and Justice Department for misleading testimony and withholding key evidence in that landmark case.