Sororicide

Sororicide is the killing of one's own sister, a term formed like the atlas's other family-killing offenses, fratricide and mariticide, from the Latin root for the victim's relation to the killer plus -cide, killing. Documented and alleged cases span from antiquity to the present: Ptolemaic Egypt's Berenice IV is said to have poisoned her sister Cleopatra VI Tryphaena in 57 BC, and Cleopatra VII later had her sister Arsinoe IV executed for treason. The Roman emperor Commodus ordered the death of his older sister Lucilla in AD 182 after she was implicated in a plot against him. Modern cases include Ronald DeFeo Jr.'s 1974 killing of his two sisters, later the inspiration for the Amityville Horror franchise, and Karla Homolka's role in the 1990 death of her younger sister Tammy. As with the atlas's other family-homicide offenses, sororicide is prosecuted under the same general homicide statutes that apply to any killing rather than as a distinct statutory offense; it functions as a descriptive category criminologists and historians use to study intra-family violence.