P.R. Laws Ap. tit. 32A, § IV, Rule 9
(A) Preliminary questions concerning the qualification of a person to be a witness, the existence of a privilege or the admissibility of evidence shall be determined by the court, subject to the provisions of subdivision (B) of this rule. In making its determinations, the court is not bound by the Rules of Evidence except those with respect to privileges.
(B) When the relevancy of the evidence introduced depends upon the fulfillment of a condition of fact, the court shall admit it upon the introduction of evidence sufficient to support a finding of the fulfillment of the condition; the court may also admit the evidence subject to the subsequent introduction of evidence sufficient to support a finding of the fulfillment of the condition.
(C) In cases heard before a jury, all the evidence concerning the admissibility of a confession by the defendant shall be heard and weighed by the judge out of the hearing of the jury. If the judge determines that the confession is admissible, the defendant may introduce to the jury, and the prosecution may rebut, evidence relevant to the weight or credibility of the confession and to the circumstances under which the confession was obtained. Other preliminary determinations may also be considered out of the hearing of the jury when the interests of justice so require or when the accused, as a witness, so requests.
(D) The accused does not, by testifying as to a preliminary matter, subject himself to cross-examination as to other issues in the case.
(E) This rule does not limit the right of the parties to introduce before the jury evidence relevant to the weight or credibility of the evidence admitted after the judge’s corresponding preliminary determination.