Poisoning at the Office

Workplace violence and the "toxic" employee.

Posted Mar 18, 2019

Used with permission from iclipart
Source: Used with permission from iclipart

We’ve all worked with (or for) someone with whom we didn’t click. Some of us have had the misfortune of working in a toxic environment, i.e., in an office where everyone is motivated by personal gain (power, money, fame or special status) and uses unethical or mean-spirited methods to manipulate and annoy those around them.  Few of us, though, have worked in a place where an employee is literally using toxic methods on his or her work colleagues. 

But it happens. While workplace violence most often conjures up images of a gun-toting employee with a grudge or an enraged ex who shows up at the office, there have been some recent workplace poisoning cases that remind us that not all workplace violence starts, or ends, with a bang. Here are some real-life stories of workplace poisoning that resulted in serious damage and, in some cases, death.

German Employee Suspected of Killing 21 Co-Workers

For years, employees at a manufacturing business in the German town of Schloss Holte-Stukenbrock had been getting sick.  So, when an employee noticed a strange white substance on his ham-and-cheese sandwich, it didn’t take him long to alert his manager.  To their credit, company personnel took his concerns seriously; they notified police and installed a surveillance camera in the break room. 

What they discovered was horrifying.  There on the camera appeared 56-year-old machinist Klaus O taking his coworker’s lunch out of the lunchbox, sprinkling white powder on the sandwich, and carefully rewrapping it and replacing it back in the communal refrigerator.  The mysterious powder turned out to be lead acetate, a heavy metal that can cause organ failure and death.  When police searched Klaus’ home, they discovered a makeshift chemist’s laboratory and a host of dangerous substances, including quicksilver, lead, and mercury. 

Klaus O worked for the same company for 38 years and is now suspected of poisoning 21 work colleagues from as far back as 2000.  On Thursday, March 7, 2019, he was sentenced to life in prison.  The exact victim count – and his motive – may never be known.  Klaus O did not say a word at his trial and none of his work colleagues reported any history of conflict or ill will between the perpetrator and his victims.  A psychologist at his trial said that Klaus O was “experimenting” on his colleagues to see how his home-brewed toxins would affect his targets; this motive would be extremely unusual but not unprecedented. 

Watch Your Water Bottle at Work

In September 2018, two BMW employees were arrested after a surveillance camera captured them taking a coworker’s water bottle from the service area and then replacing it at a later time.  The employee/victim became ill after taking a drink and realizing, due to the foul taste, that he was no longer drinking water.  He later checked himself into a local hospital, where tests revealed his drink had been spiked with engine coolant.   So far, police officials haven’t commented on a possible motive, but have made it clear they don’t think it was meant to be a prank. 

In July 2018, the motive was pretty ordinary – revenge over an argument.  A few days before, 38-year old Zoa Carmilla McIntyre and her coworker/victim had exchanged some heated words.  While the victim thought the conflict was over, she discovered otherwise after her tongue became numb and she felt sick to her stomach after drinking from a water bottle, she had left in a common area at the vet clinic where she worked. The victim took the water bottle with her to the hospital, where she – and the water in the bottle – tested positive for barbiturates that had recently been acquired by the veterinarian for use in the clinic.  Once again, a security camera solidified the evidence against the perpetrator, clearly showing that McIntyre was the only person to touch the victim’s water bottle.

If I Can’t Have You, I’ll Kill Your Mother

While there is still some controversy over who actually killed 60-year-old Mary Louise Yoder, in 2015, 24- year-old Kaitlin Conley was convicted of first-degree manslaughter and sentenced to 23 years-old Kaitlyn Conley was found guilty of first-degree manslaughter and sentenced to 23 years in prison after her boss—and ex-boyfriend's mother— was poisoned to death with colchicine. Conley had worked for the victim, 60-year-old chiropractor Mary Louise Yoder, for four years and allegedly killed her ex-boyfriend's mom as a way of getting back at him.

The Bottom Line

Toxic work experiences can run the gamut from an unsupportive manager to a company culture that fosters favoritism, gossip, lying and deception, and competition between work colleagues.  They can arise from lax hiring practices to turning a blind eye to employee misconduct to failing to provide security measures that can protect against, or spot, unethical or illegal workplace behavior.  In each of the cases above, a surveillance camera in common work areas was pivotal in providing proof that insidious workplace violence was afoot.  If only our interpersonal technology at spotting a rogue employee were as precise.    


If you're interested in forensic psychology topics, check out Dr. Johnston's forensic radio show, true crime youtube channel, and website.