Adultery is when a married person has sex with someone who is not their spouse. The person who committed adultery can swear an affidavit admitting this. An affidavit is a written statement of facts that is sworn or affirmed before a Commissioner for Oaths (or Notary Public) and filed with the court as evidence in court. If the person who committed adultery will not admit to it, you must prove adultery with other evidence. Last updated: March 2021