Crazy, Not Insane review: Why do people become murderers?

True-crime shows focusing on the act of murder are booming. Alex Gibney’s new documentary Crazy, Not Insane instead looks at what might spawn a killer

By Elle Hunt

Crazy, Not Insane

Alex Gibney

On Sky in the UK from 1 December and streaming on HBO in the US

THERE is a scene in Crazy, Not Insane, a documentary about the work of forensic psychiatrist Dorothy Otnow Lewis, where she recalls the day Martin Scorsese rang. The director was shooting Cape Fear, and had heard of Lewis’s study of violent murderers. Robert De Niro, playing a psychopath, wanted to meet one. Could she possibly make an introduction?

“It was so funny,” says Lewis in the film, clearly still tickled by the memory. “I felt …