Book excerpt: Historian Alan G. Gauthreaux chronicles 12 homicide cases from late 1800s and early 1900s Louisiana--where "unwritten law" justified jilted women who killed their paramours, and police took measures to protect defendants from lynch mobs. Stories include the 1907 kidnapping of seven-year-old Walter Lamana by the New Orleans "Black Hand," the 1912 acquittal of Zea McRee (a woman of "good reputation") in Opelousas, and the 1934 trial and execution of Shreveport's infamous "Butterfly Man."