Leviticus 5:14-19; 7:1-7; and 14:12-18 describe the trespass offering (KJV, NKJV) or guilt offering (NIV, ESV, NASB). Leviticus 19:20-22 (a man sleeping with a slave who is engaged to another man) and Numbers 6:9-12 describe two practical situations that would necessitate a guilt offering (a Nazarite who accidentally violates his vows). This is not to be confused with the sin offering.
When a person unintentionally violated some of the Lord's holy things, a trespass/guilt offering was required. "Holy things" would normally refer to things dedicated to the Lord, such as the sanctuary itself or the portion of the offerings reserved for the priests. It is not specified how this could happen inadvertently, but it is possible that a person forgot to fulfil a vow, made a mistake in fulfilling it, accidentally ate food reserved for priests, or mistakenly ate a firstborn animal from his own flock. In these cases, the offender was required to bring a sacrificial animal (an unblemished ram or male lamb) to offer as well as compensate the priests by an additional 20% for what they had been denied. (Many of the offerings made to the Lord were given to the priests and Levites; this was the Lord's provision for their support because they had no land of their own.) Instead of an animal, the offender could bring the price of the animal in silver. When a person with a very sensitive (perhaps oversensitive) conscience suspected that he had sinned against holy property, he could bring the trespass/guilt offering "just in case," but no restitution was made to the priests in that situation.
The trespass offering was also brought when someone violated the rights of another person. In this case, the offender was required to repay damages plus 20% in addition to performing the animal sacrifice.
In a trespass offering, a ram or male lamb was slaughtered; the blood was splashed on the altar, and some of the blood was applied to the person making the offering's right ear lobe, right thumb, and right big toe. Then oil was applied to the same locations, and the person making the offering's head was anointed. The majority of the sacrificial animal was burned, but the priests were able to consume some portions while in the sanctuary.