I’ve mentioned before that my general approach to mystery writing is to first write out the murder from the murderer’s perspective, including whatever mistakes the murderer made. This is basically a prose story of only mild interest in this form—what makes it interesting is being told (more or less) backwards, from the detective’s perspective. He starts with the murder and the clues and works back to what happened before and during the murder, then eventually to further back about why it happened.
I’m currently on that stage in (the tentatively titled) He Didn’t Drown in the Lake. I’d love to talk about how I’m working it out, except I can’t really do that with anyone who might actually want to read the book, since it would spoil the book. That leaves me with people who wouldn’t want to read the book, but they probably don’t want to read it because it doesn’t interest them. So there’s really no one to talk about it with.
That’s not quite 100% true, as I do have a nerd friend or two who are sufficiently interested in biology and chemicals and what-not that they will discuss the very narrow aspect of poisons, if I wanted to go the route of poisons.
Just as an aside: one of the real problems with poisons, from a mystery writer’s perspective, is that getting reliable information on dosing and effects is very hard to come by. Take this like from the Wikipedia page on nicotine poisining:
Standard textbooks, databases, and safety sheets consistently state that the lethal dose of nicotine for adults is 60 mg or less (30–60 mg), but there is overwhelming data indicating that more than 0.5 g of oral nicotine is required to kill an adult.
The other problem is that poisons almost require being passed in food or drink. Aside from skin-contact poisons, which are rare, hard to get, and dangerous for the murderer, other routes of delivering poison will let the victim know, and it takes a while to die or pass out from any sort of reasonable dose. This gives the victim a lot of time to call out for help or mark the murderer, both of which are sub-optimal from the murderer’s perspective.