Cal. Evid. Code § 1421 : CALIFORNIA EVIDENCE CODE — WRITINGS — AUTHENTICATION AND PROOF OF WRITINGS — MEANS OF AUTHENTICATING AND PROVING WRITINGS — References known only by claimed author TEXT PDF A writing may be authenticated by evidence that the writing refers to or states matters that are unlikely to be known to anyone other than the person who is claimed by the proponent of the evidence to be the author of the writing. Ca. Evid. Code § 1421 Enacted by Stats. 1965, Ch. 299.