P.R. Laws Ap. tit. 32A, § IV, Rule 76
Pursuant to the requirements of the previous rule, below are some examples, among others, of authentication or identification:
(A) Authenticity by handwriting evidence. — A writing may be authenticated by evidence of the genuineness of the handwriting of the maker. For those purposes, a nonexpert witness may state his opinion as to the genuineness of the handwriting of the supposed writer on the basis of his familiarity with the latter’s handwriting, if such familiarity has not been acquired for purposes of the litigation. Authenticity may also be shown by the trier’s or expert’s comparison of handwriting of the writing in controversy with another duly authenticated writing.
(B) Voice identification. — Identification of a person’s voice, whether heard firsthand, or through mechanical or electronic recording, by opinion based upon hearing the voice at any time under circumstances connecting it with the voice of the alleged speaker.
(C) Telephone conversations. — Telephone conversations may be authenticated or identified by evidence that a call was made to the number assigned at that time by the telephone company to a particular person or business, if:
(1) In the case of a person, circumstances, including self-identification, show the person answering to be the one called.
(2) In the case of a business, the call was made to a place of business and the conversation was related to business reasonably transacted over the telephone.
(D) Ancient documents. — When it is found that a writing has been in existence for twenty (20) years or more at the time it is offered, and that it is generally respected and acted upon as authentic by persons having an interest in knowing whether it is genuine, and that, at the time of discovery, was in a place where, if authentic, it would likely be, the writing will be sufficiently authenticated, unless its condition is such as to cast serious doubts over its authenticity.
(E) Writings in reply. — A writing may be authenticated by evidence that the writing was received in reply to a communication sent to the person who is claimed by the proponent of the evidence to be the author of the writing.
(F) Content of writings. — 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 matter.
(G) Authentication by admission. — A writing or any other material may be authenticated by evidence that the party against whom it is offered has at any time admitted its authenticity, or by evidence that the writing has been accepted as authentic by the party against whom it is offered.
(H) Wills. — A will executed in Puerto Rico shall be authenticated in accordance with the applicable laws.