[Modus operandi of insane offenders in multiple homicides]

Homicides committed by insane offenders have been rarely investigated from the forensic point of view in a comprehensive and detailed manner. The objective of the study was to describe and characterize the modus operandi and personal characteristics in cases when more than one victim was killed and the perpetrator was deemed insane in judicial proceedings. Differences between single and multiple-vitim homicides in the population of insane murderers were also examined. Complete dossiers and forensic examination reports of 21 homicide victims killed by 9 individuals were retrospectively analyzed. The comparative control group consisted of 41 cases with only one victim killed by a single insane perpetrator. The offence and offender variables were subjected to a comparative statistical analysis. The results indicated some specific factors that can be regarded as distinctive features more commonly observed in multiple vs. single victim killings perpetrated by insane individuals. There was a significant correlation between, psychosis with depressive delusions, emotional/affective motivation, common domicile and a positive relationship between the perpetrator and the victim, infanticide committed in the perpetrator's offspring, actions with elements of planning, attacking victims while asleep, attacking from the back rather than from the front, concentration and clustering of injuries in one region of the body and multiple psychotic homicides. The results and conclusions of this study can provide practical, useful implications for homicide investigations, offender profiling or forensic psychiatric and psychological evidence.