The Ordeal Bean
The Code of Hammurabi is one of the oldest written books of law in human civilization. In this text, it claims that the calabar bean is essentially like a magical plant put on Earth by God to help humans find out the truth. These beans are extremely poisonous, and anyone who eats them would become really sick, and die, or have permanent damage for the rest of their life. The theory behind this method was that if this person was innocent, God would have mercy on them and help them recover from the illness and go back to normal. If they died, it meant they were guilty.
It turns out that there was a way to survive this ordeal, but very few people probably figured it out before it was too late. If someone swallows a calabar bean whole, they are far more likely to survive without getting too sick, because the skin of the bean will hold in the toxins. It is possible that it could pass through the digestive system without doing any damage at all. But if someone bit down and chewed on the bean, it would release the poison immediately, and they were far more likely to die as a result.
The beans contain physostigmine alkaloid, which is one of the chemicals that is used to produce nerve gas. People lose complete control over their nervous system’s connection to their internal organs. They begin having seizures, and it can lead to brain damage and asphyxiation. Since ancient people strongly believed that evil acts were influenced by demons, they would have seen someone convulsing and having seizures as proof that the demon had possessed them to do the crime.