Lawyers for Vice President Sara Duterte on Monday argued that the Supreme Court’s ruling voiding her first impeachment complaint established binding constitutional standards for impeachment proceedings, rejecting claims that key portions of the decision were merely incidental remarks.

Defense spokesperson and counsel Michael Poa told senator-judges that the high court’s discussion on what constitutes an impeachable offense was not obiter dicta — legal commentary not necessary to decide a case and therefore not binding — but part of the reasoning that supported its ruling.

Sen. Alan Peter Cayetano earlier questioned whether the Supreme Court’s statements requiring impeachable acts to be committed during an official’s current term formed part of the Court’s controlling doctrine or were simply observations outside the main issue it resolved.

Poa maintained that the passages were integral to the Court's constitutional reasoning.

"The Supreme Court did not make a distinction as to the guidelines it laid down in that decision," he told senator-judges.

He said the Court's July 2025 ruling, which unanimously struck down the first impeachment complaint against Duterte for violating the Constitution's one-year bar rule, went beyond resolving a procedural issue and established due process standards governing impeachment proceedings.

"While the end result was that the one-year bar was triggered, what the Supreme Court was really discussing was the observance of due process in every stage of the proceeding," Poa said.

In its ruling, the Supreme Court said due process protections apply even before an impeachment case reaches the Senate, including during proceedings in the House of Representatives. 

It also stated that “the basis of any charge must be for impeachable acts or omissions committed in relation to their office and during the current term of the impeachable officer.”

The defense has relied on that language to argue that allegations involving Duterte’s actions before she became vice president cannot form the basis of the current impeachment case, a position that could restrict the scope of evidence presented by prosecutors.

Poa said the Court’s discussion was central to its conclusion because it explained the constitutional limits on impeachment proceedings.

"The end does not justify the means," Poa said, quoting the ruling. "It was precisely discussing the means—what are the processes that we should follow."

The prosecution rejected the defense’s interpretation, saying the Supreme Court decision dealt with a different legal issue and did not dictate how the Senate should conduct the present impeachment trial.

House prosecutor Chel Diokno argued that the 2025 ruling was issued before the Senate impeachment court had begun proceedings and therefore could not have addressed issues arising from the current trial.

"There is no trial yet to speak of when the Supreme Court rendered that decision," Diokno said. 

"How could what is happening now in the trial have been an issue when the decision was rendered," he added.

Diokno argued that the passage cited by the defense addressed the nature of impeachable offenses rather than the procedures governing the Senate trial.

"This doesn't really tell us how to conduct the trial," he said. "This basically tells us that if we don't follow that, we're in danger of having a trial that's void from the beginning."

The defense maintained that legal questions arising during an impeachment trial remain subject to judicial review, despite the Senate's constitutional role as the impeachment court.

Responding to Cayetano's hypothetical on whether either party could challenge Senate rulings before the Supreme Court, Poa said they could do so if they believed the impeachment court had committed grave abuse of discretion.

"The Constitution cannot be read in isolation," he said. "If one party believes there was grave abuse of discretion, we are of the position that this is a justiciable issue and can be brought before the Supreme Court."

Cayetano noted that while a Senate conviction or acquittal cannot be appealed, the impeachment court has previously recognized the Supreme Court's authority to resolve legal questions arising during impeachment proceedings. 

He cited the 2012 impeachment trial of then Chief Justice Renato Corona, when the Senate voted to comply with a Supreme Court temporary restraining order preventing the disclosure of Corona's foreign currency accounts. 

The senator said the episode demonstrated that while the Senate alone decides whether to acquit or convict, it has previously acknowledged the high court's authority over constitutional and procedural issues affecting an impeachment trial.