P.R. Laws Ap. tit. 34A, § II, Rule 188
The court may grant a new trial for any of the following grounds:
(a) When new evidence is discovered, which, if presented at the trial, would probably have changed the verdict or the finding of the court and which the defendant could not, with reasonable diligence, have discovered and produced at the trial. When a motion for new trial is made upon this ground, the defendant shall present the new evidence together with his motion in affidavits of the witnesses by whom such evidence is expected to be given.
(b) When the verdict has been decided by lot, or by means other than a fair expression of opinion on the part of all jurors.
(c) When the verdict is contrary to law or evidence.
(d) When any of the following circumstances intervened and as a consequence thereof the substantial rights of the defendant were impaired:
(1) When the defendant was not present at any stage of the trial, except as provided in Rule 243.
(2) When the jury has received any evidence out of the court other than that resulting from a view of the premises.
(3) When the members of the jury have separated without leave of the court, after retiring to deliberate upon their verdict, or when any member thereof has been guilty of any misconduct by which a fair and due consideration of the case has been prevented.
(4) When the prosecuting attorney has been guilty of any misconduct.
(5) When the court has erred in the decision of any question of law arising in the course of the trial, or when the court has erroneously instructed the jury in a matter of law, or has erroneously denied an instruction to the jury requested by the defendant.
(e) When it is impossible to obtain a transcript of the stenographic notes of the proceeding because of the death or incapacity of the court stenographer or because of the loss or destruction of said notes, or to prepare a statement of the case in a narrative form as provided by Rules 208 and 209 to substitute for said transcript.
(f) The court may also grant a new trial, when due to any other cause for which the defendant is not responsible, he has not had a fair and impartial trial.