I see that very soon they are adding "berry picking" and I for one think it would be an awesome feature if they added poisonous ones also. In order to tell if they are poisonous are not they could make it so the player must inspect the berries. (Poisonous berries could have a specific mark on them that determines that they are indeed poisonous). I can just imagine someone leaving berries on the ground in a building and just observe the building from a distance, waiting for a starving survivor (who is oblivious to the fact they are poisoned) to eat them.
