bill bryson's book on the summer of 1927 has a long segment on the sacco and venzetti murders, and notes that the 1920s were sort of this golden age of murder--cheap guns, fast transportation, (prohibition feeding organized crime), but the feds were still pre-New Deal size, local police departments were hamstrung by small budgets and jurisdictional boundaries and forensics basically boiled down to 'hope we find fingerprints and they match a suspect'