P.R. Laws Ap. tit. 32A, § IV, Rule 59
(A) Appointment. — Whenever the court determines, before or during the trial, that expert testimony is needed, the court may, of its own motion or at the request of any party, appoint one or more experts to investigate and to render a report as may be ordered by the court, or to testify as expert at the trial. The court shall fix the compensation for such services.
(B) Compensation. — In all criminal actions or juvenile court proceedings, the compensation fixed shall be paid from the State’s funds. In all civil actions, the compensation fixed shall be paid by the parties in such proportion as the court may determine and shall be thereafter chargeable as other costs or disbursements pursuant to the law.
(C) Appearance and examination. — An expert appointed by the court pursuant to this rule may be called to testify and examined by the court or by any party. Whenever he is called and examined by the court, the parties may cross-examine him as in the case of any other witness.
(D) Right to produce other expert evidence. — Nothing in this rule shall prevent any of the parties from producing other expert evidence on the same fact or matter to which the testimony of the expert witness appointed by the court relates. If the party calls its own expert witness, his fees shall be paid by said party but said fees shall not be taxed as costs unless the court at its discretion provides otherwise.