Born and brought up in Derbyshire, Hegarty was mostly educated in convent schools before reading English at Newcastle University. After graduating, she took a course in criminal law. She worked initially for the Metropolitan Police and later the Crown Prosecution Service.
She has won several awards, including the Crime Writers' Association Duncan Lawrie Dagger for Blood From Stone in 2008 and the Silver Dagger for Deep Sleep. In addition, her novel, Safer than Houses was nominated for the Duncan Lawrie Dagger in 2006. She also writes psychological thrillers under the name of Frances Hegarty, among them, The Playroom, Half Light and Let's Dance, which was published in 1995. Her novels have been translated into 14 languages. Several have been adapted for television. Fyfield's Helen West series has twice been adapted for television.