The characteristics of the offered item itself, considered in the light of circumstances, afford authentication techniques in great variety. Language patterns may indicate authenticity or its opposite. Since aural voice identification is not a subject of expert testimony, the requisite familiarity may be acquired either before or after the particular speaking which is the subject of the identification, in this respect resembling visual identification of a person rather than identification of handwriting. The cases are in agreement that a mere assertion of his identity by a person talking on the telephone is not sufficient evidence of the authenticity of the conversation and that additional evidence of his identity is required. The additional evidence need not fall in any set pattern.
Outgoing calls made by the witness involve additional factors bearing upon authenticity.
The calling of a number assigned by the telephone company reasonably supports the assumption that the listing is correct and that the number is the one reached. If the number is that of a place of business, the mass of authority allows an ensuing conversation if it relates to business reasonably transacted over the telephone, on the theory that the maintenance of the telephone connection is an invitation to do business without further identification. Otherwise, some additional circumstance of identification of the speaker is required. The authorities divide on the question whether the self-identifying statement of the person answering suffices. Public records are regularly authenticated by proof of custody, without more.