Women who commit deadly violence are different in many ways from male perpetrators, both in terms of the most common victims, the way in which the murder is committed, the place where it is carried out and the perpetrator's background. This is shown by a new study that also investigated homicide trends over time in Sweden.

Sweden is in the group of countries with the lowest number of murders per capita. As in other parts of the world, the majority of cases of deadly violence are committed by men: In nine cases out of ten, the perpetrator is a man.

It is also men that have been the main focus of studies in this area. We know less about the characteristics of women who commit deadly violence, because they have been the subject of far fewer studies.

A Swedish research group has now investigated how the frequency of male and female perpetrators of deadly violence has changed during the years 1990-2010. The study also investigates the similarities and differences between male and female perpetrators.

The group of researchers from Sahlgrenska Academy, Karolinska Institutet, Stockholm University, the National Board of Forensic Medicine and the National Council for Crime Prevention studied data covering all cases of deadly violence in Sweden during the years between 1990 and 2010.

There were 1570 cases of deadly violence committed during the observed time period, and of them 1420 were committed by men (90.4%) and 150 by women (9.6%). The gender distribution of the perpetrators was stable at around 90/10% men/women throughout the investigation period.

One clear trend is that the frequency, in other words the number of cases of legal violence per capita, decreased.

"The results show that deadly violence decreased, both in terms of male and female perpetrators. The study also showed that the proportion of female perpetrators in relation to men largely remained constant during the time period studied," said Thomas Nilsson, Researcher at Sahlgrenska Academy, University of Gothenburg.

The researchers were able to see several differences between men and women who committed deadly violence.

"There were more pronounced differences between male and female perpetrators with adult victims compared with when the victim was a child (under 15 years). The adult victims of female perpetrators were more often male and an intimate partner. The victims were often under the influence of substances at the time of the crime and they died mostly due to knife violence," said Thomas Nilsson, Researcher at Sahlgrenska Academy.

Another difference was that previous violence between the victim and the perpetrator was more common in cases of female perpetrators than male perpetrators, and that women more frequently committed crimes in the home environment. The home was the most common murder scene for all cases but it was even more common for female perpetrators, where the murder took place in the home in nearly 9 out of 10 cases.

The differences were fewer when the victim was a child.

However, female perpetrators more frequently used asphyxia, namely, suffocation, compared with male perpetrators who committed deadly violence against a child. The female perpetrators also had fewer instances of sentences for previous criminal activity, according to the prosecution records of the National Council for Crime Prevention.

"One result in which Sweden is different from what was seen in studies from other countries is that female and male perpetrators are just as likely to commit suicide in cases where the victim is a child. According to these studies, suicide after infanticide is more common among female perpetrators compared to men," said Thomas Nilsson.

Variables that were different between the sexes, regardless of whether the victims were adults or children, were those related to the classification of the offense and if the perpetrator had a severe mental disorder, respectively.

Women were assessed to have carried out the crime under the influence of a severe mental disorder more often than men. Crimes committed by women were more frequently classified as manslaughter or infanticide (due to the fact that only women can be convicted of infanticide), while crimes committed by men are more frequently classified as murder or involuntary manslaughter by assault.

The majority of perpetrators, regardless of gender, committed the deadly violence with an adult victim under the influence of some substance (alcohol or drugs), while this was only true for a minority of perpetrators with child victims.

In summary, the study shows that the frequency of deadly violence has decreased in sweden during the period 1990-2010. Male and female perpetrators with child victims are more similar than those with adult victims. Another important conclusion is that female perpetrators represent less than one tenth of all perpetrators when the victim is an adult, but account for more than one third of the cases of deadly violence where the victim is a child.

The results show that there are fundamental differences between female and male perpetrators of deadly violence, which should be considered in the development of gender-specific risk assessment tools and risk management strategies. Future studies should focus on , among other things, the distinct role that the influence of substances appears to play when it comes to deadly violence against adults and children. The research group believes there is also a need for further studies on time trends of female perpetrators and deadly violence.

"Finally, the social and criminological differences we found between male and female perpetrators of deadly violence should be taken into account in the implementation of preventative measures, and the effectiveness of these measures should in turn be evaluated in future research. These measures should focus in particular on issues relating to the relationship between the victim and the perpetrators as well as the crime scenes, since the primary differences between male and female perpetrators appear in those areas," said Thomas Nilsson, researcher at Sahlgrenska Academy.