In a five-month period in 1972-3 Herbert Mullin killed 13 persons in California in cold-blooded, apparently motiveless murders. Mullin came from a decent background, but drifted into drug-use and was unable to cope with the grief resulting from the death of a young friend. He became withdrawn and dissolved into schizophrenia - a mental condition for which he was diagnosed and treated in hospital.

When eventually captured, Mullin spoke of hearing voices which commanded him to kill. A California jury failed to find him legally insane out of the fear that the state’s mental institutions would not hold him, or would prematurely release a killer into the community. Instead Mullin was found guilty and sentenced to life imprisonment.