Deaths by homicidal poisoning date back to ancient times. In early Rome, for example, the most effective way to eliminate a political rival was arsenic—a tasteless, water-soluble toxin that could easily be added to drinks. Murderers in medieval Europe often used juice extracted from the berries of the deadly nightshade bush to carry out their dirty deeds.
Until the 19th century, poisons could not be traced or detected in the human body, making them the perfect weapon. Today, with sophisticated toxicology, homicidal poisonings are rare. There’s also no such thing as a “perfect poison.” Poisons have changed over time, but, in this day and age, all poisons can be traced and detected.
Joni Johnston, a forensic psychologist and private investigator, has researched and written extensively on criminal poisoning and murder by poisoning. A&E True Crime spoke with Johnston to explore the ancient legacy of poisonings, the psychological profile of a homicidal poisoner and common myths and misconceptions about those who poison.
From a historical perspective, what have been some of the common poisons used in murders?
That certainly depends upon the time and availability, as well as the ability to detect certain poisons. But I think a good place to start is arsenic, which was made famous in many cases. It goes back to Roman times, where it was used to poison political rivals. In the 1800s, arsenic was in its heyday. It was commonly used for a number of household remedies and killing insects and rats, making it readily available. Then, in 1836, a chemist by the name of James Marsh became the first person to find a way to detect arsenic in the human body. Because it could now be traced, it fell into disuse.
Cyanide, which is a chemical, is another poison that has been used in various murders, including some mass murders. One of the reasons that cyanide stands out is because it works so fast. Then you have thallium, which gained somewhat of a reputation for being a poison that some foreign secret police have used in assassinations. It is tasteless and takes several days for symptoms to show up. So, it creates some distance between the event of the poisoning and when a person dies.
None of these are typically used today. Now, most poisonings are done with some kind of common household item, like antifreeze or medication.
Why do some people choose poison as their method of murder over something quicker or less complicated like a gun or their own hands?
There are a couple of general explanations for people choosing poison. We know that poisoners are overrepresented in medical professions, for example. So, it just may be the familiarity some people have with toxic substances that makes them choose this method. They know how to administer it and have access to it. The same is true in terms of caretakers, whether that’s in the home or in a nursing home.
There are also some psychological explanations. Poisoning somebody, in a weird kind of way, gives the perpetrator a sense of psychological distance from the murder. They’re not banging somebody over the head with a baseball bat or putting their arms around someone’s throat. They don’t even have to be right there for that person to die if they administer the poison over a long period of time and the person gradually deteriorates.
What is the typical psychological profile of a poisoner? What about the victims? Do they have certain traits or characteristics that make them a target?
If you look at the motives of poisoners, and then look at their victims, one of the things you’ll see is that money stands out—[it’s] a pretty common motive when it comes to poisoning. Revenge is a secondary motive. We know that 90 percent of poisoners kill someone they know.
It’s difficult to look at personality traits, but I do think when you study some of the people who have used poison, you’ll find them described as mild-mannered and as people who get along with just about everyone. They also tend to be conflict-avoidant. These individuals, in comparison to other murderers, are sneakier and much less confrontational. They’re oftentimes people nobody suspects.
Poisoners, as a group, are smarter than many other murderers because poisoning requires methodical planning. With this group, you’ll also see this vulnerable kind of narcissism. They need to get what they want, like an insurance payout, and believe they deserve whatever reward they’re seeking. Like other murderers, they often lack empathy and have a sense of entitlement.
What are some of the key issues that investigators and prosecutors face when determining a homicidal poisoning and taking a case to trial?
Detecting a poison, and not mistaking a homicide as part of a natural disease process, is critical for investigators. For prosecutors, proving intent is a big issue. Was a poisoning accidental or did the accused intend to kill the victim? How do you show that a person intended to harm and kill another? You have to show that the person you are prosecuting had access to the poison detected and was responsible for administering it to the deceased. You need to prove that the poison wasn’t self-administered or administered by accident.
In one case, a woman [Lana Clayton] poisoned her husband with eyedrops. She claimed that he always drank two drops of the substance mixed with water because it helped him to have a bowel movement. Prosecutors were able to prove otherwise. There are a lot of working pieces with a poisoning, which can make these cases difficult to detect, solve and prosecute.
What are some common misconceptions or myths surrounding homicidal poisoners?
There’s a misconception that poison is no longer used because of our ability to detect these chemicals and toxins. Statistically, poisoners are a lot rarer than they used to be, but they are out there. On the flip side, there’s this idea that certain poisons are untraceable—a perfect poison, if you will, but there’s no such thing. There’s also this perpetual myth that most homicidal poisoners are women when, in fact, about 60 percent of poisoners are men. When you look at weapon of choice, women are much more likely to pick poison than men, but there are more male murderers.
Is there one case of homicidal poisoning that stands out as notable for you? Or one that is particularly sinister or disturbing?
A case from Germany really stands out. The murderer’s name was Klaus O. German privacy laws prohibit his last name from being publicly divulged or published. He had worked for a metal fittings company for almost 40 years. People described him as a loner. He kept to himself but did a great job at work.
In March of 2018, one of his coworkers discovered some kind of white powder in their sandwich. He went to his manager and they installed a hidden security camera in the breakroom. They caught footage of Klaus unwrapping his coworkers’ lunches and sprinkling this powder on them. At first, they thought it was a prank, but many employees had become ill over the years and some even died.
After it was reported, authorities discovered this makeshift chemist lab in Klaus’s house. He had mercury, lead and a variety of other toxic metals and substances. It’s believed that he was responsible for as many as 21 deaths, stemming back to 2000, with many more fellow employees becoming sick or suffering permanent kidney and brain damage.
A psychologist who talked to Klaus and testified at his trial said it sounded like he was experimenting on his colleagues like they were lab rats. Klaus received a life sentence in March 2019.