A mug shot or mugshot (an informal term for police photograph, or booking photograph), is a photographic portrait typically taken after a person is arrested.[1][2] The original purpose of the mug shot was to allow law enforcement to have a photographic record of an arrested individual to allow for identification by victims and investigators.
Photographing of criminals began in the 1840s only a few years after the invention of photography, but it was not until 1888 that Alphonse Bertillon standardized the process.
Above quote is from Wikipedia.
