As mentioned before (see commentary on Leviticus 4:13), guilt is not something which is pronounced (in a judicial sense) upon an individual, but realized (in a subjective sense) through various means. In this particular instance, a curse was included on anyone who failed to come forward as a witness. It may be that under the effects of the curse the individual began to feel guilty.
2 or if anyone touches an unclean thing, whether a carcass of an unclean wild animal or a carcass of unclean livestock or a carcass of unclean swarming things, and it is hidden from him and he has become unclean, and he realizes his guilt;