Grounds for a defamation lawsuit include certain expressions of opinion that intentionally cause harm or false statements of fact, HG.org says. Filing a defamation lawsuit requires proof of the defamation and consequent damages, whether personal, financial or professional.
Statements that are true, even if they are negative, or that contain negative opinions without a deliberate intent to harm are protected by the right to free speech and generally are not grounds for a defamation lawsuit, HG.org notes.
In order for a defamation lawsuit to meet the necessary requirements, the statement must cause actual harm to the intended subject. For example, if the subject loses his job as a result of the false statements, that qualifies him to sue. Proof is necessary, and this can include audio recordings, witness statements or another type of record of the statement.
Statements that occur during legislative or judicial hearings, statements made between spouses, and statements made according to the law are not grounds for a defamation lawsuit, FindLaw advises. A defendant may be allowed certain conditional privileges if the statement was made in service of a publisher's interest, to protect the interests of a third party, or to protect the well-being of a family member.