Short answer. Yes. At any time after the appeal from the lower court has been perfected, and before the Court of Appeals' judgment convicting the appellant becomes final, the appellant may move for a new trial on the ground of newly-discovered evidence material to his defense. The window is the pendency of the appeal itself.
What the law says
At any time after the appeal from the lower court has been perfected and before the judgment of the Court of Appeals convicting the appellant becomes final, the latter may move for a new trial on the ground of newly-discovered evidence material to his defense.
Rule 124, Section 14 — Motion for new trial. Read the full provision →
The appeal does not freeze the search for the truth
A common assumption is that once the case leaves the trial court, the evidence is closed and only arguments remain. Rule 124 says otherwise for one specific situation: at any time after the appeal from the lower court has been perfected and before the judgment of the Court of Appeals convicting the appellant becomes final, the latter may move for a new trial on the ground of newly-discovered evidence material to his defense. If a witness surfaces, a document emerges, or a piece of physical evidence comes to light while the appeal is running, the appellant is not condemned to watch the appeal proceed on an incomplete record.
The boundaries of the window
Both ends of the period matter. It opens when the appeal has been perfected — the case must actually be on appeal, not merely headed there. It closes when the Court of Appeals' judgment convicting the appellant becomes final — after which the extraordinary character of finality takes over and this motion is no longer available. Notice also who may move: the latter, meaning the appellant. This is a remedy for the person fighting the conviction, on the ground the rule names — newly-discovered evidence material to his defense — not a general re-opening tool for any party dissatisfied with the record.
Not every late arrival is "newly discovered"
The ground has a name, and the name is a test. Evidence is not newly discovered merely because it is newly presented: the motion must conform with the Rules' requirements for new-trial motions on this ground, and the substance of those requirements is that the evidence could not have been found and produced at trial with reasonable diligence, and that it is material — capable of mattering to the defence, not cumulative of what the court already weighed. An affidavit that a known witness has changed his story, or a document that sat in the accused's own drawer through trial, will be measured against that standard sceptically.
Moving fast and moving properly
If something has genuinely surfaced, act on both fronts at once. Preserve the evidence — sworn statements from the new witness, originals or certified copies of the new document, and a clear account of when and how it was found, since the discovery story is part of the motion's merits. And get it to appellate counsel immediately: the motion must be filed in the pending appeal before the judgment of conviction becomes final, and the appeal itself continues moving while the motion is prepared. Newly discovered evidence delayed into finality is newly discovered evidence wasted.