Before evidence is admitted, its proponent must produce evidence sufficient to support a finding that it is what it is claimed to be. The bar is low; the process is easy to overlook.
Methods. Testimony of a witness with knowledge; comparison by an expert or the factfinder with an authenticated specimen; distinctive characteristics including appearance, contents and internal patterns; and evidence about a process or system.
Self-authenticating items include certified public records, official publications, newspapers, trade inscriptions, acknowledged documents, commercial paper, certified business records, and certified records generated by an electronic process.
Electronic evidence. Emails are authenticated by address, content, reply patterns and testimony. Text messages by phone records, content and context. Website content by testimony of the person who captured it, with date and URL, supported where necessary by archival services. Social media requires more than the account name, because accounts are impersonated.
Hash values and certification by a qualified person authenticate data copied from a device or storage medium.
Produced documents. A document produced by a party in discovery is generally treated as authentic as against that party, which is the cheapest authentication available and is routinely forgotten.