1,099. A Toddler Who Brings in Chometz

Chometz u’Matzah 2:9

If someone saw a toddler enter a house that was already searched with bread in his hand, followed that child and found crumbs, the house need not be searched again because we are confident that the child ate the bread and dropped these crumbs. This is because small children typically crumble food when eating, while mice don’t. If one doesn’t find any crumbs, the house must be searched again.

Chometz u’Matzah 2:10

Let’s say that nine piles of matzah and one pile of chometz were put aside, then a mouse took something and entered a house that was already searched. If we don’t know what the mouse took, the house must be searched again because whenever there is a doubt about things that are established, it is treated as if they are 50/50 (and not, as one might think in this case, 9 to 1. See Talmud Pesachim 9b for more on this halachic principle).