In 1994, Frederick West was arrested and accused of murdering twelve young women. But it was the trial of his wife, Rosemary West, that became Britain's serial-killer trial of the century...

Detained for the murder of the twelve women found at 25 Cromwell Street, Gloucester, Frederick West hung himself on New Year's Day 1995. The case had enraged the nation, and the subsequent trial of Rosemary for the same crimes caused a media sensation.

How are ordinary human beings driven to become serial killers? How did this psychopath ensnare so many women? And how much was Rosemary truly involved?

Brian Masters attended the Rosemary West trial on a daily basis. In "She Must Have Known" he produces a penetrating study of the sexual obsession that led to a series of horrifying and measured killings, ultimately leaving the reader to make up their own mind on the guilt of Rosemary West.