P.R. Laws Ap. tit. 32A, § IV, Rule 49
(A) Subject to subsection (C) of this rule, if a witness, either while testifying or prior thereto, uses a writing to refresh his memory with respect to any matter about which he testifies, such writing must be produced at the hearing at the request of an adverse party, and unless the writing is so produced, the testimony of the witness concerning such matter shall be stricken.
(B) If the writing is produced at the hearing, the adverse party may, if he chooses, inspect the writing, cross-examine the witness concerning it and introduce in evidence such portion of said writing that may relate to the testimony of the witness.
(C) Production of the writing is excused at the trial, and the testimony of the witness shall not be stricken, if the writing:
(1) Is not in the possession or control of the witness or the party who offered the testimony concerning the matter; and
(2) Said writing was not reasonably procurable by such party through the use of process or orders for the presentation of documentary evidence or through any other available means.