Psychopaths know no pity, have no conscience and show no remorse. They may be your boss, your friend, even your spouse. Would you recognise one if you saw one?

Not all psychopaths are serial murderers or rapists. There are several different types of psychopaths - some are more difficult to identify than others.

Here is a rundown of some of the world's most famous serial killers, their crimes, punishment and psychological traits.