Female serial killers are not unknown (see, for example, Patricia Pearson’s When She Was Bad), but they are less common than their male counterparts and tend to play by different rules. Most female serial killers that we know of have, for obvious reasons, used different methods than men. Poison is a particular favourite way of dealing with their victims. In addition, women tend to not be as sexually compelled as men when it comes to serial murder. It has been suggested that all (male) serial killers are acting out a form of sexual violence, which is a slight overstatement but not by much. Women, on the other hand, seem driven by other motives.
Sheila LaBarre was an exception to all these rules. Technically she might not have met the strictest definition of a serial killer since she only admitted to the murder of two men, but there’s reason to think there may have been more. What makes her case stand out is how her violence took a very masculine form: physical domination driven by a perverse and hyper-aggressive sexuality.
Kevin Flynn doesn’t go into any of this background in his book on the LaBarre story, but has nevertheless produced an excellent account, well paced and surprisingly well structured. LaBarre herself is revealed as a sadistic bully; not insane (at least as ultimately determined by a jury) but mean. Could she have been stopped? Society has to do a better job identifying such types and responding to them.