No person shall be twice put in jeopardy of punishment for the same offense.This constitutional mandate is echoed in Section 7 of Rule 117 of the Rules of Court which provides:
Section 7. Former conviction or acquittal; double jeopardy. – When an accused has been convicted or acquitted or the case against him dismissed or otherwise terminated without his express consent by a court of competent jurisdiction, upon a valid complaint or in information or other formal charge sufficient in form and substance to sustain a conviction and after the accused had pleaded to the charge, the conviction or acquittal of the accused or the dismissal of the case shall be a bar to another prosecution for the offense charged or for any attempt to commit the same or frustration thereof, or for any offense which necessarily includes or is necessarily included in the offense charged in the former complaint or information.
x x x x x x x x x
Under this provision, double jeopardy occurs upon (1) a valid indictment (2) before a competent court (3) after arraignment (4) when a valid plea has been entered and (5) when the accused was acquitted or convicted or the case was dismissed or otherwise terminated without the express consent of the accused. Thus, an acquittal, whether ordered by the trial or appellate court, is final and unappealable on the ground of double jeopardy.
The only exception is when the trial court acted with grave abuse of discretion or, as we held in Galman v. Sandiganbayan, when there was mistrial. In such instances, the OSG can assail the said judgment in a petition for certiorari establishing that the State was deprived of a fair opportunity to prosecute and prove its case.
The rationale behind this exception is that a judgment rendered by the trial court with grave abuse of discretion was issued without jurisdiction. It is, for this reason, void. Consequently, there is no double jeopardy.