Poisoning is intent. If I leaves a cup of some liquid with a clear warning that it has not be tested for being drinkable, I don’t think that I’m liable for you being poisoned when you go and drink it. Especially if I do not sell drinks. Of course, there are regulations about safety, but they are mostly about when you’re at risk of being harmed while I use my tools for myself. They’re not about you ignoring warnings labels and getting harmed.

IANAL.