Defamation in terms of Criminal Law:

• Section 499 of The Indian Penal Code defines 'defamation' as being committed:
• by words, either spoken or intended to be read, or by signs or visible representation.
• Any person who makes or publishes any imputation concerning any person,
• knowing or having reason to believe that such imputation will harm, the reputation of such person, is said, to defame that person.

Exceptions :

1.  Imputation of truth which public good requires to be made or published.—It is not defamation to impute anything which is true concerning any person, if it be for the public good that the imputation should be made or published. Whether or not it is for the public good is a question of fact.
2. Public conduct of public servants.—It is not defamation to express in a good faith any opinion whatever respecting the conduct of a public servant in the discharge of his public functions, or respecting his character, so far as his character appears in that conduct, and no further.
3. Conduct of any person touching any public question.—It is not defamation to express in good faith any opinion whatever respecting the conduct of any person touching any public question, and respecting his character, so far as his character appears in that conduct, and no further.
4. Publication of reports of proceedings of Courts.—It is not defamation to publish substantially true report of the proceedings of a Court of Justice, or of the result of any such proceedings.
5. Merits of case decided in Court or conduct of witnesses and others concerned.—It is not defamation to express in good faith any opinion whatever respecting the merits of any case, civil or criminal, which has been decided by a Court of Justice, or respecting the conduct of any person as a partly, witness or agent, in any such case, or respecting the character of such person, as far as his character appears in that conduct, and no further.
6. Merits of public performance.—It is not defamation to express in good faith any opinion respecting the merits of any performance which its author has submitted to the judgment of the public, or respecting the character of the author so far as his character appears in such performance, and no further.
7. Censure passed in good faith by person having lawful authority over another.—It is not defamation in a person having over another any authority, either conferred by law or arising out of a lawful contract made with mat other, to pass in good faith any censure on the conduct of that other in matters to which such lawful authority relates.
8.  Accusation preferred in good faith to authorised person.—It is not defamation to prefer in good faith an accusation against any person to any of those who have lawful authority over that person with respect to the subject-matter of accusation.
9. Imputation made in good faith by person for protection of his or other's interests.—It is not defamation to make an imputation on the character of another provided that the imputation be made in good faith for the protection of the interests of the person making it, or of any other person, or for the public good.
10. Caution intended for good of person to whom conveyed or for public good.—It is not defamation to convey a caution, in good faith, to one person against another, provided that such caution be intended for the good of the person to whom it is conveyed, or of some person in whom that person is interested, or for the public good.

If a person is found guilty of having committed defamation according to Section 499 of the IPC, the punishment is stipulated in Section 500: simple imprisonment for a term which may extend to two years, or fine, or both. The CrPC, which lays down the procedural aspects of the law, states that the offence is non-cognisable and bailable. Those who are accused of the offence would generally not be taken into custody without a warrant, and as such, an aggrieved person would not be able to simply file a police complaint but would, in most cases, have to file a complaint before a magistrate.

Defamation under Civil Law:

As far as defamation under tort law is concerned, as a general rule, the focus is on libel (i.e. written defamation) and not on slander (i.e. spoken defamation). In order to establish that a statement is libellous, it must be proved that it is (i) false, (ii) written; (iii) defamatory, and (iv) published, [according to Ratanlal and Dhirajlal, The Law of Torts, 26th Edition; page 279].