A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
lev 5:1TRESPASS OFFERINGS FOR CONCEALING KNOWLEDGE. (Lev 5:1)
if a soul . . . hear the voice of swearing--or, according to some, "the words of adjuration." A proclamation was issued calling any one who could give information, to come before the court and bear testimony to the guilt of a criminal; and the manner in which witnesses were interrogated in the Jewish courts of justice was not by swearing them directly, but adjuring them by reading the words of an oath: "the voice of swearing." The offense, then, for the expiation of which this law provides, was that of a person who neglected or avoided the opportunity of lodging the information which it was in his power to communicate.
lev 5:2TOUCHING ANY THING UNCLEAN. (Lev 5:2-3)
if a soul touch any unclean thing--A person who, unknown to himself at the time, came in contact with any thing unclean, and either neglected the requisite ceremonies of purification or engaged in the services of religion while under the taint of ceremonial defilement, might be afterwards convinced that he had committed an offense.
lev 5:4FOR SWEARING. (Lev 5:4-19)
if a soul swear--a rash oath, without duly considering the nature and consequences of the oath, perhaps inconsiderately binding himself to do anything wrong, or neglecting to perform a vow to do something good. In all such cases a person might have transgressed one of the divine commandments unwittingly, and have been afterwards brought to a sense of his delinquency.
lev 5:5it shall be, when he shall be guilty . . . that he shall confess that he hath sinned in that thing--make a voluntary acknowledgment of his sin from the impulse of his own conscience, and before it come to the knowledge of the world. A previous discovery might have subjected him to some degree of punishment from which his spontaneous confession released him, but still he was considered guilty of trespass, to expiate which he was obliged by the ceremonial law to go through certain observances.
lev 5:6he shall bring his trespass offering unto the Lord for his sins which he hath sinned--A trespass offering differed from a sin offering in the following respects: that it was appointed for persons who had either done evil unwittingly, or were in doubt as to their own criminality; or felt themselves in such a special situation as required sacrifices of that kind [BROWN]. The trespass offering appointed in such cases was a female lamb or kid; if unable to make such an offering, he might bring a pair of turtledoves or two young pigeons--the one to be offered for a sin offering, the other for a burnt offering; or if even that was beyond his ability, the law would be satisfied with the tenth part of an ephah of fine flour without oil or frankincense.
lev 5:15sin through ignorance, in the holy things of the Lord, &c.--This is a case of sacrilege committed ignorantly, either in not paying the full due of tithes, first-fruits, and similar tribute in eating of meats, which belonged to the priests alone--or he was required, along with the restitution in money, the amount of which was to be determined by the priest, to offer a ram for a trespass offering, as soon as he came to the knowledge of his involuntary fraud.
lev 5:17if a soul sin . . . though he wist it not, yet is he guilty--This also refers to holy things, and it differs from the preceding in being one of the doubtful cases,--that is, where conscience suspects, though the understanding be in doubt whether criminality or sin has been committed. The Jewish rabbis give, as an example, the case of a person who, knowing that "the fat of the inwards" is not to be eaten, religiously abstained from the use of it; but should a dish happen to have been at table in which he had reason to suspect some portion of that meat was intermingled, and he had, inadvertently, partaken of that unlawful viand, he was bound to bring a ram as a trespass offering [Lev 5:16]. These provisions were all designed to impress the conscience with the sense of responsibility to God and keep alive on the hearts of the people a salutary fear of doing any secret wrong.