Senators acting as judges in the impeachment trial of Vice President Sara Duterte may face legal challenge including criminal cases if they proceed with changing the two-thirds voting requirement for her conviction, according to former presidential spokesman Salvador Panelo.

The Palace backed the former Supreme Court justices' view that the decision on the voting threshold for convicting Vice President Sara Duterte lies solely with Senate impeachment court.

Senators JV Ejercito and Raffy Tulfo want the Supreme Court to decide on the voting threshold to convict or acquit Vice President Sara Duterte amid a possible deadlock due to the continued absence of four senators.