Assessment of causal associations between illness and criminal acts in those who are acquitted by reason of insanity.

Background: The court proceedings after the terrorist attacks on 22 July 2011 reignited the debate on the justification for having a rule that regulates the insanity defence exclusively on the basis of a medical condition – the medical principle. The psychological principle represents an alternative that requires a causal relationship between the psychosis and the acts committed. In this article we investigate rulings made by the courts of appeal where the accused have been found legally insane at the time of the act, and elucidate the extent to which a causal relationship between the illness and the act appears to be in evidence.

Material And Method: Data have been retrieved from rulings by the courts of appeal published at lovdata.no, which include anonymised rulings. Searches were made for cases under Section 39 (verdict of special sanctions) and Section 44 (acquittal by reason of insanity) of the General Civil Penal Code. Court rulings in which a possible causal relationship could be considered were included. The included rulings were carefully assessed with regard to whether a causal relationship existed between the mental disorder of the accused at the time and the criminal act. The search returned a total of 373 rulings, of which 75 were included.

Results: The vast majority of the charges referred to serious crimes. Diagnoses under ICD-10 category codes F20-29 (schizophrenia, schizotypal and delusional disorders) were the most frequently occurring type. In 17 of the 75 rulings (23%), it was judged that no causal relationship between the illness and the act existed. In 25 of 26 cases that involved homicide, a causal relationship between the illness and the act was judged to be evident.

Interpretation: The data may indicate that the medical principle results in impunity in a considerable number of rulings where the illness of the accused apparently has had no effect on the acts committed.