women who kill
Women kill for different reasons and in different ways than men according to a new study. Istock

Women who commit murders differ greatly from male perpetrators, both in terms of who and how they kill, scientists have said. These differences were more pronounced when the victim is an adult than when it is a child.

Homicide committed by female offenders is an understudied phenomenon and very little is therefore known about what motivates some women to choose the path of deadly violence. In nine cases out of 10, murderers are men and they are the focus of most scientific research.

Studying a large Swedish cohort of male and female murderers, researchers from the Ahlgrenska Academy, Karolinska Institutet, Stockholm University, the National Board of Forensic Medicine and the National Council for Crime Prevention, revealed sex-differences in how murders were carried out – with women more likely to kill men they know.

Violence in the home

The study – published in the International journal of Forensic Mental Health – estimates the incidence rates of male-perpetrated and female-perpetrated homicides over two decades (1990-2010) in Sweden. In total 1,570 killings were identified. The data suggests a decline in the incidence of both male-perpetrated and female-perpetrated homicide during that time, as well as stable proportions of female offenders. However, big differences between who the victims were and how they were killed were observed.

For one, female murderers appeared more likely to kill men than other women, and in particular they more frequently took the lives of their intimate partners using knives.

"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," says study author Thomas Nilsson, Researcher at Sahlgrenska Academy.

Often these women appeared to have been submitted to violence within their homes from the men they ended up killing. While the home was the most common murder scene for all cases, it was therefore even more common for female perpetrators, nearly in 9 out of 10 cases. Regardless of gender, the victim was in many cases under the influence of drugs or alcohol.

Violence against children

When they killed children, men and women did so for similar reasons, and were both more likely to commit suicide afterwards. However, female perpetrators more frequently used asphyxia than male perpetrators and also had fewer instances of sentences for previous criminal activity.

Right now, these findings are only applicable to Sweden and further research will be needed to better understand the way women who kill think and how violence can be prevented.

"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," concluded Nilsson.