Who was the first person to categorize poisons into six groups based on their effects?

The first person to categorize poisons into six groups based on their effects was MJB Orfila. His work in toxicology laid the foundations for the scientific study of poisons and their impact on human health. In the early 19th century, Orfila conducted extensive research on the effects of various substances and formulated a classification system that organized poisons based on their characteristics, which significantly advanced the field of forensic toxicology. This approach provided a systematic way of understanding and analyzing the potential dangers of different toxic agents, which is still relevant in modern toxicological studies.

In contrast, other notable figures like Alexander Gettler, Charles Norris, and Jean Servais Stas contributed to forensic toxicology as well, but they did so in different contexts and time periods. Gettler is recognized for his work in the early 20th century and advancements in analytical techniques, Norris made significant contributions in the realm of toxicological reporting and administration, and Stas was known for his isolation techniques of poisons. However, it was Orfila who first established the foundational classification of poisons, which is why he is identified as the correct answer in this context.