Mass Killers Are Often Not Criminally Insane, Study Suggests


Ben Taub


Ben Taub

Freelance Writer

Benjamin holds a Master's degree in anthropology from University College London and has worked in the fields of neuroscience research and mental health treatment.

Freelance Writer

549 Mass Killers Are Often Not Criminally Insane, Study Suggests
Anders Breivik was incorrectly diagnosed as insane. LISE ASERUD / Stringer

Most of us like to think that no one in their right mind would knowingly commit an atrocity like a mass shooting, although some researchers are now arguing that you don’t have to be unhinged or deranged to carry out such acts. After reviewing the case of Anders Breivik – who shocked the world in 2011 by killing 77 people, many of them teenagers at a youth camp on the Norwegian island of Utøya – they suggest that he and many other villains may in fact act out of “extreme overvalued beliefs,” rather than insanity.

The Breivik case provides the perfect illustration of just how foggy the boundary between sanity and insanity is: After his arrest, he was assessed by a team of psychoanalysts who diagnosed him as a paranoid schizophrenic. However, seeking a second opinion, the authorities referred the case to a second team, who found him to be nonpsychotic, concluding that he acted with full use of reason.


According to a new study that appears in the Journal of the American Academy of Psychiatry and the Law, such diagnoses are extremely hard to make because psychotic disorders have no clear definition, and are assessed in relation to a spectrum of symptoms. For instance, schizophrenia is associated with delusions, yet the paper explains that “there are no essential elements to a delusion,” thereby leaving it up to the opinion of psychiatrists as to whether a person is acting reasonably or in a deluded way.

In relation to the Breivik case, the researchers point out that prior to committing his crimes, he posted a compendium of beliefs online, outlining his racist and xenophobic views. According to the study authors, these views, though extreme and fundamentalist, cannot be labelled delusional, since it is clear that Breivik came to his misguided conclusions via rational means: He took many of his ideas from cultural or historical figures, before editing and refining these into a manifesto of his own.

As such, the researchers are calling for the term “extreme overvalued belief” to be introduced to the legal framework, and to be applied to “criminally violent behavior when psychosis can be ruled out.”

Mental illness is notoriously difficult to diagnose in criminal cases. Ronald Sumners/Shutterstock


In a statement explaining this finding, study co-author Tahir Rahman explained that “people think that violent actions must be the byproduct of psychotic mental illness, but this is not always the case. Our study of the Breivik case was meant to explain how extreme beliefs can be mistaken for psychosis.”

He goes on to claim that “in courts of law, there are not clearly defined, standard methods of diagnosing insanity for legal purposes," adding that "this new term will help forensic psychiatrists properly identify the motive for the defendant's criminal behavior when sanity is questioned."

For instance, the study cites a number of other mass killers, such as Oklahoma City bombers Timothy McVeigh and Terry Nichols, as examples of those whose actions can be explained by “extreme overvalued beliefs” rather than mental illness.


  • tag
  • schizophrenia,

  • psychosis,

  • insane,

  • criminal,

  • paranoia,

  • mass killing,

  • murderer,

  • Anders Breivik