Originally Posted by MSD

Let's talk contact poison. Dimethylmercury is an obvious one, .1ml can be enough to kill someone, and they'll appear asymptomatic for months before they die slowly and painfully, too late for intervention.

Then there's dimethyl sulfoxide. Great stuff, and anything you can dissolve in it will be absorbed through the skin and into the bloodstream. If you can get a few drops on someone, you can do the job. Golden poison frogs' secretions will kill at 100 micrograms, tetrodonic acid (blowfish poison) at about 500 micrograms. Both are soluble in DMSO.

I'm sure you can figure our how to splash a few milliliters of liquid on someone in public and make it look like an accident, if they even notice.

I believe that killing is wrong other than in defense or just war, so no.