Despite standing as chief prosecution witness in the Moors Murders trial, David Smith was vilified by the public due to the accusations thrown at him by Myra Hindley and Ian Brady about his involvement in their crimes. Hindley's later confession that she and Brady had lied in an attempt to reduce their sentences did little to diminish the slurs against his name.

For almost 45 years, Smith was asked by writers and film-makers to tell his story. Apart from a handful of brief interviews, he always refused. Carol Ann Lee met Smith during her research for One of Your Own, her critically acclaimed biography of Hindley, following which he finally agreed to reveal all.

In Witness, interviews, archival research and, most significantly, David Smith's own vivid memoir are fused to create an unforgettable, often harrowing account of his life before, during and after the Moors Murders.