Does anyone know of the process and reliability of using hemlock leaves to ctb?
There are more than one type of hemlock: the tree, water hemlock, and poison hemlock. The Canadian Hemlock tree is not poisonous (although for clarity's sake, you still probably shouldn't eat it!). Water hemlock and poison hemlock are both poisonous, but with different compounds causing their toxicity.
Water hemlock, of which there are five subspecies is deadly within hours if ingested. Symptoms are seizures, rapid heart rate, frothing at the mouth, and respiratory distress. Death comes via a final, horribly long seizure.
Poison hemlock is very similar, with minor differences in the roots and leaves. The root and the liquid it contains is deadly toxic (the rest of the plant is not as poisonous, but will still make you sick), with similar symptoms to those of water hemlock, but death in this case comes because respiratiry paralysis stops the victim from being able to breathe.
As far as I'm concerned death from either of the hemlocks would be quite painful.