Research has shown that psychopaths are worse at recognising fear in other people. However, not all psychopaths are criminals and not all criminals are psychopaths. Portuguese researchers compared 22 criminal psychopaths, 16 non-criminal psychopaths, 11 criminal non-psychopaths and 13 people who were neither criminals or psychopaths. Participants were shown a series of faces and asked to press a button whenever they saw one expressing fear. The study found that the psychopaths, regardless of whether they had a criminal record, were much worse at detecting fear and telling it apart from other emotions. Both the criminal groups were more impulsive and less inhibited than the other participants.
Iria, Catarina and Barbosa, Fernandon - Perception of facial expressions of fear: comparative research with criminal and non-criminal psychopaths Journal of Forensic Psychiatry and Psychology February 2009, 20(1), 66-73