There has been little in-depth research about female serial murderers, perhaps because compared to males, there are relatively few. It has been estimated that 83% of serial killers are male (90% of murderers are male).
This article highlights some of what is known about female serial murderers and it is based on the research of Elizabeth Gurian, who studied two separate groups of female serial offenders: 30 cases of serial male and female partnerships (partnership refers to a partnership or relationship of male and female offenders in a group of two or more) and 35 cases of individual/solo female serial offenders. Gurian’s research included offenders from countries all over the world, though the majority were in the United States, mainly from California, Texas and Florida.
Aileen Wuornos (1990) was the first American female serial killer, as labeled by the FBI, though some argue that there have been others prior to Wuornos. Solo female serial killers have historically tended to target family members for the purpose of profit. Many used poison as their primary method of murder.
Below are the main results of Gurian’s study:
In summary, mixed-sex partnered groups were more likely to target adult or teen strangers. They used a combination of methods to kill their victims and were driven by pleasure-oriented motives. Solo murderers were more to likely target family members than partnered groups, tended to use singular methods of murder and were driven by purpose-oriented motives (i.e. money). When solo murderers did kill strangers, their victims tended to be weak and helpless and included hospital patients, the elderly or infants.
Source: Gurian, E. A. (2011). Female serial murderers: Directions for future research on a hidden population. International Journal of Offender Therapy and Comparative Criminology, 55 (1), 27-42.