The Guilt Offering in a Case of Doubt
The guilt-offering, brought in a case of doubt where a person is uncertain if he transgressed a commandment unintentionally, is actually more expensive than a sin-offering, which is brought when a person is sure that he transgressed.
This is an indication that, in certain respects, the person who is uncertain if he sins is actually in need of more atonement.
When a person knows that he has sinned, he is aware that something needs correcting, which leads him to act upon his feelings.
If he is uncertain that he sinned, he is likely to take the matter less seriously, and this represents a more serious spiritual blemish, for the person becomes indifferent to his own spiritual shortcomings. Thus a more powerful - and more expensive - atonement is needed.
Source: Likutei Sichos Lubavitcher Rebbe
An individual is required to repent and bring a sin-offering even for an unintentional transgression.
This is difficult, noted the Alschich HaKadosh R' Moshe Alshich, for there are certain unintentional transgressions which are completely out of a person's control. For example, if a man was walking in the street and, suddenly, something frightened him and he jumped back a step. As a result, he stepped on, and broke, his friend's vessel. What could he have done to prevent this from happening? Nothing, apparently. How can he be held responsible in such a case?
When a man consistently keeps Hashem's mitzvos, answered the Alshich, Hashem protects him from all mishap. For instance, if a person is always careful not to allow any food of questionable kashrus status into his mouth, then Hashem will see to it that he will never unintentionally eat anything forbidden. Similarly, a person who is always mindful of other people's property will not unintentionally sin with money that does not belong to him.
This idea, concluded the Alshich, is alluded to in the following verse: If a person unintentionally transgresses..." - When does a person come to sin unintentionally? When he "does one of them" - when he has previously committed the sin intentionally.
Source: Rabbi Yisrael Bronstein