Shulchan Arukh Yoreh De'ah · Siman 3

English

Seif 1 The slaughter of non consecrated (animals) does not require intention. Even if one didn’t intend to cut, or if one threw the knife and inserted it itself in a wall, and (in that manner) slaughtered (properly) according to Halacha. If one sees that the knife is not dulled between the required (integral) points or under the skin.And if one finds that a feather or a hair is cut by it, for sure it's not dulled.Even if he drops the knife from his hand or his foot with intention, and slaughters, it is permissible.However if it falls on its own, its forbidden, Because we require human power..(to perform it properly).And if there was a knife placed on your lap or your hand and it fell from your hand or lap by mistake, because it fell literally on its own, it is forbidden.