An autopsy provided minimal insights, and further examination indicated that Mary may have been poisoned. Tests were conducted to detect various toxins, including arsenic, cyanide, and other common poisons. After several weeks, the results returned negative.

A poison control specialist proposed the possibility of Colchicine, a medication used for gout that has a narrow therapeutic range. This implies that the difference between effective and harmful doses is slight, with some doses potentially overlapping
In its unadulterated form, Lisi informed producers that even a minuscule quantity can be fatal.

In October 2015, laboratory analyses confirmed that Mary Yoder, who did not suffer from gout, had a lethal concentration of Colchicine in her bloodstream.


Was it possible that she ingested something that was unintentionally contaminated? Or had she been deliberately administered the drug? Investigators concluded it was the latter.