Well, I can understand why some those things can be seized. Nightshade, Croton, Jimson Weed, and Hemlock, for instance, can kill you. Of course, as with any of them, much depends upon the plant itself and the soil it's grown in to determine its potency.
You can even graft common tomato to Jimson Weed. It produces HUGE tomatoes and about 50% of them will have no effect upon the eater. The rest can (and have) caused problems ranging from hallucinations to a quick and painful death. Croton Oil, a VERY powerful purgative, comes from Croton and a very little goes a very long way -- a little too much and you die, running at both ends.