I am looking for the easiest way for one protagonist to kill another one. They are acquaintances and do spend some together drinking coffee or tea, so I was thinking poisoning would be the easiest solution.
When talking about "easy", I think the following criteria should be taken into consideration:
- How hard is it to get/make?
- How much does it cost?
- How does it manifest itself?
- Is it traceable?
Murderer gets rid of the body, so factor 4. is not so important for my story. So far, I have thought of arsenic and potassium cyanide.
Do you know of any others? Is there some online resource where I could find out more about these things?