A man who received a certificate of innocence after spending 33 years in prison in the 1987 death of his mother-in-law and her mother has filed a federal lawsuit against the city of Chicago, his lawyer said Monday.Robert Smith, 72, alleges eight former Chicago police detectives working under former commander Jon Burge beat him into confessing the crime. The lawsuit filed in U.S. District Court also names the former Cook County prosecutor who took his statement.Attorney Stuart J. Chanen of Chanen & Olstein in …