WASHINGTON - While probing organized crime in New England since the 1960s, the FBI used killers as informants, shielded them from prosecution and knowingly sent innocent people to jail, House investigators said Thursday in concluding a two-year inquiry. The bureau's conduct "must be considered one of the greatest failures in the history of federal law enforcement," according to the final report from the House Government Reform Committee. "Federal law enforcement personnel tolerated and probably encouraged false testimony in a state death penalty case just to protect their criminal informants," said Rep. Dan Burton, who started the investigation when he was...