Burge was indicted by the Feds, but not for torture. He was indicted for perjury--i.e. for lying when he said he and his men did not torture people.
The statute of limitations had indeed inspired, but that proves my point. To see why, you have to understand a little bit about Illinois politics. When allegations against Burge first surfaced (in 1982!), Richard M. Daley--now mayor of Chicago--was Cook County States Attorney. His office did nothing. His successor [censored] Devine, had to recuse himself from the case because he had once DEFENDED Burge against charges of torture in a civil trial. Devine's successor, Lisa Madigan, also failed to take any action. To this day, men who were tortured by Burge continue to languish in prison; Madigan has yet to review any of their cases.
In short, Burge and his cronies got away with torture because the entire system--from the CPD's Office of Professional Standards to the Cook County States Attorney's Office--let him get away with it. Had any ordinary citizen been systematically torturing people in this way, this NEVER would have happened--they'd have been locked UNDER the @#$% jail for the rest of their lives.