Defamation per se refers to words that injure a person’s reputation without the need to prove the injury has occurred. Per se is a Latin term meaning "by itself" or "inherently". Defamation per se can occur in writing or when spoken orally. If a person writes defamatory statements about another person, the law calls it libel. When a person expresses defamatory language orally, then the law deems it slander.

The law in a case of defamation per se presumes the injury, which eliminates the plaintiff’s need to prove injury to his reputation. For example, a local newspaper asserts that a person sexually abused a child. This statement is clearly damaging to a person’s reputation. Hence, it would not be necessary for the person to prove the statement caused injury to his reputation or standing in the community. That does not prevent the newspaper from raising possible defenses to the defamation per se charge, if sued.

The law recognizes four types of defamation per se in slander cases. The first type is a statement that a person has a loathsome disease. This category is usually restricted to claims of sexually transmitted diseases. The second type is a statement that a person committed a crime of moral turpitude, which means the crime was especially vile or despicable, such as rape or incest. A person suing under these categories would not need to prove special damage, because they are classified as defamation per se in slander.

The third category of defamation per se in slander is a statement that a person was not chaste. Chaste means a person is a virgin or refrains from sexual intercourse. This historically has been used most often in reference to women. A person suing under this category also would not need to prove damage.

The final category is a statement that negatively affects a person’s reputation relating to his business or profession. For example, an accountant could file a lawsuit for defamation per se against someone who makes verbal statements that the accountant is dishonest in his practice or lacks the skill to perform his job. In this type of case, the defamatory statement must directly relate to the person’s job. A negative statement unrelated to the job would not fall under this category.

Most jurisdictions consider libel to be defamation per se. This usually means that a person only needs to prove that a defendant used defamatory language concerning the plaintiff and that defendant published it in some manner. An ordinary plaintiff in libel cases does not need to prove damages, because the law presumes harm. If a plaintiff is a public figure or the matter concerns a matter of public interest, then the plaintiff may need to prove additional elements, including the falsity of the statement and fault on the part of a defendant. Some jurisdictions require a plaintiff in libel cases to prove special damage, if the libel is not obviously defamatory.