ABSTRACT
Although research on perpetrators has consistently shown that most perpetrators are not insane, some are. They are a small but significant group that is the exception to the rule and have mental deficiencies and will be called the Deranged. The deficiencies are generally caused by certain biological defects that interact with a particular environment which then lead to crimes. They suffer from mental or even personality disorders, are narcissists or psychopaths or suffer from psychotic disorders like schizophrenia which makes them delusional. Many, although not all, show a disturbing lack of empathy. There are strong parallels between mass shooters, school shooters and certain terrorists. The latter are mainly the lone wolves and suicide attackers who, compared to other terrorists, show a much higher likelihood of having mental impairments. The two case studies which are discussed more in depth are Ted Kaczynski, the Unabomber, and Anders Breivik. the Norwegian terrorist who killed 77 people on Utoya and in Oslo. Lastly, is a discussion on how the rise of Islamic State of Iraq and Syria (ISIS) with its openly propagated extreme violence made it become very attractive for very violent and disturbed people who were already involved in crimes, like Bouhlel the man who drove a truck into a crowd on 14 July 2016 in Nice.
