Short answer. Affidavits or authenticated documents. Rule 37, Section 2 provides that a motion for new trial based on newly discovered evidence, the ground in paragraph (b) of the preceding section, must be supported by affidavits of the witnesses expected to give that evidence, or by duly authenticated documents proposed to be introduced in evidence.
What the law says
A motion for the cause mentioned in paragraph (b) shall be supported by affidavits of the witnesses by whom such evidence is expected to be given, or by duly authenticated documents which are proposed to be introduced in evidence
Rule 37, Section 2 — Contents of motion for new trial or reconsideration and notice thereof. Read the full provision →
What the law says
shall be supported by affidavits of merits which may be rebutted by affidavits
Rule 37, Section 2 — Contents of motion for new trial or reconsideration and notice thereof. Read the full provision →
What the law says
The motion shall be made in writing stating the ground or grounds therefor, a written notice of which shall be served by the movant on the adverse party
Rule 37, Section 2 — Contents of motion for new trial or reconsideration and notice thereof. Read the full provision →
What the law says
A motion for new trial shall be proved in the manner provided for proof of motions
Rule 37, Section 2 — Contents of motion for new trial or reconsideration and notice thereof. Read the full provision →
What the law says
A pro forma motion for new trial or reconsideration shall not toll the reglementary period of appeal
Rule 37, Section 2 — Contents of motion for new trial or reconsideration and notice thereof. Read the full provision →
What Section 2 requires for newly discovered evidence
Rule 37, Section 2 is specific about what has to support this kind of motion: "A motion for the cause mentioned in paragraph (b) shall be supported by affidavits of the witnesses by whom such evidence is expected to be given, or by duly authenticated documents which are proposed to be introduced in evidence." Newly discovered evidence is the ground the preceding section lists as paragraph (b), so this is the proof requirement that applies to your motion.
How this differs from the other ground for new trial
The same section handles the other ground listed in the preceding section differently. For a motion citing that other ground, paragraph (a), the requirement is different: "shall be supported by affidavits of merits which may be rebutted by affidavits." Newly discovered evidence, by contrast, is treated separately, with its own proof requirement built around the witnesses or documents behind the evidence itself, rather than affidavits of merit.
The general requirements for any motion for new trial
Before getting to the specific proof requirement, Section 2 sets out what any motion for new trial has to do procedurally: "The motion shall be made in writing stating the ground or grounds therefor, a written notice of which shall be served by the movant on the adverse party." It also states that "a motion for new trial shall be proved in the manner provided for proof of motions." The affidavits or documents discussed above are what satisfies that proof requirement for a newly-discovered-evidence motion specifically.
Why getting the proof right matters
Section 2 closes with a warning worth taking seriously: "A pro forma motion for new trial or reconsideration shall not toll the reglementary period of appeal." A motion that fails to actually satisfy the required support — here, affidavits of the witnesses or duly authenticated documents behind the newly discovered evidence — risks being treated as pro forma. That has a real consequence: it would not pause the running of the period you have to appeal, on top of leaving the motion itself weak on its merits.