Behind the unveiling of J.K. Rowling as the author of a pseudonymously published detective novel lies a messy and not-terribly-precise science called “forensic stylistics”. Using specially designed software — or, less often, just a trained eye — experts in the field try to match writing styles and discern the true authorship of disputed texts. But, even when they turn out to be right, as in the Rowling case, their findings are less than exact. Linguist Ben Zimmer explores the field and its usefulness at The Wall Street Journal.