If you left a poisoned pastry on the counter, surrounded by labels warning of the poison, you might think only Homer Simpson would take it. However, many adults are illiterate. Perhaps one in ten are, and among criminals, it’s probably higher. So, a warning sign doesn’t really get you off the hook for poisoning an unsuspecting person.:smack:
Am I to understand that the habanero-donut ploy is a go? 
Not aimed at you. Just a misuse of quoting.
Of course not. Cough. But I’d probably not make it past voir-dire.
I’m guessing the sign is probably not specific enough (What kind of deadly traps? How many? Where are they located?) and not close enough to the actual traps themselves to constitute proper a proper warning. For example, there are usually multiple signs for an electric fence located on the fence itself, with both a written and symbolic warning. Plus, the fence is a visual warning itself. The fence isn’t invisible or designed to look like a fluffy bunny mural.
As a bit of a hijack, what if you leave a poisoned tuna salad with a big fat sign saying “this tuna is poisoned, I am trying to solve my rodent problem” and the neighbors’ cat enters, eats it and dies? Are you culpable for that loss?
If you know that the neighbor’s cat often enters your kitchen and you’ve made no effort to keep it out and know it could enter your kitchen again and eat the poison tuna then I’d say yes. Maybe not legally but ethically. If the cat’s never done it before that you’re aware of I’d say no.
But with regard to the OP’s question I don’t think it matters. Your responsibility towards a human’s safety compared to an animal’s is quite different. If you run over a cat (and you’re not an asshole) you stop, check on the animal to see if you can help, and if not maybe give your condolences to the owner. If you run over a person the process is a bit different unless you want to end up in jail.
Did you put the poison out with the intent to kill your neighbor’s cat? If so, then yeah.
Intent was key. If you do something with the intent of killing someone, you will get in trouble if they get killed by that thing. The other circumstances- including where they were and what they were doing at the time- are not all that important.
I get that intent is the big thing (I considered that to be the “official” answer to the OP) and that you need to convince a jury of it. The thing is that there is no proof of intent, so the jury has to go on assumptions and circumstances.
The Springfield Nuclear Power Plant attorneys apparently went over the issue of the legality of poisoned donuts already (see here):