n spite of the fact that, for hundreds of years, poison has been a convenient way to speed along an inheritance or dispatch an unwanted spouse, little has been written about the personality of the criminal poisoner. Part of this may be the skill with which many poisoners have eluded authority (it wasn't until the 20th century that we were any good at detecting it), it may partly be due to stereotypes (females are consistently more often portrayed as professional poisoners), and third, it may be partly due to confounding variables (for instance, since poison is such an ideal weapon of choice, it may tell us more about the intelligence of the perpetrator than about his or her personality).
The Demographics of Death
Contrary to popular belief, the majority of convicted poisoners are men, overwhelmingly so when the victim is a woman. When the victim is a man, the poisoner is equally likely to be male or female. As with other methods of murder, perpetrators rarely cross racial lines when they decide to send a victim to an early grave, meaning African Americans tend to be poisoned by other African Americans, Caucasians by other Caucasians. etc. On average, a homicidal poisoner is 5 to 10 years younger than his/her victim.
Career-wise, homicidal poisoners are over-represented in the medical (doctor, nurse, laboratory professional) or care-taking professions (wife, mother, nursing home attendant), where they have easy access to both the means to kill and a bevy of vulnerable victims. Of course, the vast majority of poisoners knock off someone s/he knows, such as a child, spouse, friend of acquaintance.
The Poisonous Personality
Experts believe the number of convicted poisoners is just the tip of the iceberg and that, in comparison to other crimes, what we don't know about poisoners is 20 to 30 times higher. As such, we can at best talk about the personalities of poisoners who get caught. That being said, we can make some hypotheses about the personalities of poisoners by studying the nature of the crime and the personalities involved with the published cases of convicted poisonings.
Killing someone with poison, by it's very nature, requires careful planning and subterfuge, so it comes as no surprise that poisoners tend to be cunning, sneaky, and creative (they can design the murder plan in as much detail as if they were writing the script for a play). Male or female, they tend to avoid physical confrontation and, instead, rely on verbal and emotional manipulation to get what they want from others.
Convicted poisoners also tend to have a sense of inadequacy, for which they compensate through a scorn for authority, a strong need for control, wish-fulfillment fantasies, and a self-centered, exploitive interpersonal style. Often either spoiled as a child or raised in an unhappy home, some experts liken the poisoner's personality to an incorrigible child whose immature desire for his/her own way leads him/her to try to control and manipulate the world. It's as if the poisoner never grew up and is determined to take what s/he wants just as a child would from a candy store. Developmentally stunted, other people are viewed without empathy and the poisoner's internal compass is guided instead by greed or lust rather than morals. And, because poison is often not detected initially, the power and control poisoners experience with success tends to increase his or her confidence in future endeavors.
As far as the poisoners’ motives for murder, they are not much different from other homicides, in that they usually revolve around money (insurance); jealousy (“lover’s triangle”); removing an obstacle (she'll marry me if I get rid of the kids) revenge (make them pay); sadism (make them suffer); conviction (political motives, e.g. assassination, terrorism); boredom (wants to have fun by having a challenge of wits with law enforcement); and ego (belief in mental superiority). Some poisoners revel the role of tender, self-sacrificing attendant to the victim they are slowly killing; think of the cases like Jane Toppan and Dr. Harold Shipman, whose ministrations to their victims initially aroused tearful admiration and gratitude from family members.
There are of course rarer motivations for criminal poisoning. There is a form of medical child abuse known as Munchausen by Proxy, in which a perpetrator harms a child to attract sympathy and attention from others. In certain documented cases, poison has been used.
The Bottom Line
Given that 1 out of 5 verified murders by poisoning is never solved, it's hard to draw a definitive psychological profile of the typical poisoner. Those who've been caught and convicted give us some clues - clever, sneaky, emotionally immature, methodical, and self-centered. Many of them are amazingly skilled at pretending to be something they're not - a doting husband, caring nurse, or devoted friend. Behind the mask, though, lies a psyche that is propelled by childish needs and unencumbered by moral restraints.