The lethal dose is in children aged between 3 and 5, in adults 10 to 20 berries.
Speed of action can I not tell you, but all too soon it is not. Deadly it can be as from 5-10 berries or so. This varies from person to person, of course. If YOU ASK the because you want to take it as a drug .. not do that leiber, are better and less dangerous. but drugs are either way EVIL! : P
The belladonna contains in all parts of a mixture of tropane alkaloids, whose content is between 0.2 to 0.6% varies. The proportion of atropine (Stimulanzie that can lead to madness and frenzy) is very high and already ten berries are deadly.
try it not that convincing is pure hell