How do I Poison Someone?

The only way to actually poison someone is to take a Vial of Poison, combine it with a water ration, food, or a drug, and then get that person to drink the ration.

A Vial of Poison is created using Corrosive Liquid, a Battery and Pharmaceutical Products. You can then combine this with water, food or drugs to make a poisoned item. This will look completely similar to a normal item, except it will not stack with the normal items. Meaning if you have a water ration in the bank, and you deposit a poisoned water ration in the bank, you see two identical icons in the bank, and you can not know which is which.

It's not that easy to do, really. It's easier to get the town to banish him.

If the person keeps food/water/drugs in their chest (and assuming you can create the posion), a good way to do it is to steal the thing that is in their chest. Poison it, then mail it back to them, saying that you were just stealing it to get the distinction. Then you have to wait for them to actually use it. This is much more likely to happen if they are banished and don't have access to food/water/drugs from the bank.