25 best police movies ever

M (1931)

Metropolis director Fritz Lang made his move into sound film with this crime thriller – and pioneered several innovations. Not only was it the first film to use a leitmotif for a major character – Peter Lorre's child-murderer Hans Beckert whistles In the Hall of the Mountain King to sinister effect – it was also the first police procedural.

In the end, the police's use of the latest technology – fingerprinting and handwriting analysis – come to naught, and it's left to the city's criminals to catch and try the pathetic Beckert.