Symmetrical "mirror-image" injuries and the "chessboard" pattern: useful markers of self-mutilation.

The evaluation of injuries due to self-mutilation may be complicated by atypical lesions and fabricated histories of the causative events. Four cases are described where one of the most striking findings was the presence of "mirror-image" injuries and/or a "chessboard" pattern of intersecting parallel lines from self-inflicted incised wounds. Case 1: A 32-year-old man was dead in his burnt-out car, with symmetrical, "mirror-image", circular burns from the car cigarette lighter over his forehead, cheeks, ears, upper and lower arms, the dorsal and palmar aspects of the hands, the anterior chest wall including the nipples, the anterior abdomen, thighs, lower legs, and the back of his neck. The deceased had a history of psychotic depression and had died of burns and inhalation of products of combustion. Case 2: A 19-year-old woman who fabricated a history of assault demonstrated multiple, superficial, "mirror-image" injuries of her thighs and forearms. Case 3: A 32-year-old man who exsanguinated from cut wrists showed multiple, superficial, and "mirror-image" incised wounds of the wrists, with a "chessboard" pattern. Case 4: A 26-year-old man died after jumping from a building. He had multiple superficial, "mirror-image" incised wounds of his anterior chest and thighs, with a typical "chessboard" pattern. Given the difficulties that sometimes arise in determining whether injuries have been self-inflicted or not, the finding of symmetrical "mirror-image" injuries, and/or a "chessboard" pattern formed by 2 groups of regular, parallel, superficial incised wounds running at right angles to each other provides compelling evidence of self-mutilation, unless a plausible alternative explanation is available.