Who murdered mother-in-law in 1976

My wife’s mother was murdered when she was eight or nine years old. She was turned over to be raised by an aunt and uncle who only kept her and her sister for the Social Security checks. Nobody has ever seem to care what happened to the her mother or to them. Not knowing who took her mother away has greatly affected their lives. Finding out what happened my all these years later provide some kind of relief. There is an awesome story behind her murder which involves her doing some accounting for someone who later ended up on trial for a bombing in town. My mother-in-law was also friends with an associate whose body was later found headless in a pond. The FBI investigated that murder.A famous young lawyer at the time flew in from Boston to defend the defendant in the bombing. It’s all connected