Tohoros 3:6-7

Tohoros 3:6

If a person with congenital deafness, a person lacking mental competence or a minor was found in an alley that contained something ritually unclean, he is presumed to be clean, while an adult with full faculties is presumed to be unclean. Whoever lacks the ability to be questioned is presumed clean in a case of doubtful impurity.

Tohoros 3:7

If a child was found on the side of a cemetery with lilies in his hand and lilies only grew in a ritually-unclean place, he is nevertheless ritually clean. This is because one could posit that someone else gathered the flowers and gave them to the child. Similarly, if a donkey was in a cemetery, its gear remains clean.