Lawyer Israelito Torreon said on Wednesday he was preparing a Supreme Court (SC) petition challenging the Senate impeachment court’s decision on the number of votes needed to convict Vice President Sara Duterte, hours after the tribunal changed the threshold.

The Senate impeachment court voted to change the basis for calculating the threshold, ruling that only senator-judges participating in the trial should be counted. The change reduced the threshold from 16 votes to 14.

“As a matter of fact, I’m preparing a petition already in case they will decide to that effect,” Torreon said in an interview with DAILY TRIBUNE’s Straight Talk.

“We can always allege that there is grave abuse of discretion amounting to lack or excess of jurisdiction,” he added when asked whether the threshold issue could reach the high court.

The Duterte-allied lawyer said the Constitution’s impeachment provision requires a two-thirds vote of “all the Members of the Senate,” which he interpreted as referring to the full 24-member chamber rather than only those participating in the trial.

Under the Senate’s original 6 July ruling, presiding officer Francis “Chiz” Escudero interpreted the constitutional requirement to mean 16 votes, based on the full 24-member Senate.

The issue was reopened after Sen. Erwin Tulfo questioned how the phrase “all the Members of the Senate” should apply when some senator-judges are unable to participate in the proceedings.

Torreon argued that a senator’s absence, suspension, or inability to participate does not by itself remove that person from the Senate’s membership.

He cited the Supreme Court’s ruling in Bayan v Zamora, which involved the Visiting Forces Agreement, to support his interpretation of the impeachment provision.

“Bayan versus Zamora talks about the Visiting Forces Agreement. The Supreme Court there said that two-thirds of all members of the Senate means all members of the Senate; the denominator should be 24,” he said.

Torreon said that interpretation also defined the limits of the Senate’s authority in the impeachment case, arguing that its role as the constitutional body that tries and decides impeachment cases does not shield its actions from judicial review.

“The fact that the Senate is the sole judge of impeachment cases does not mean that it can go outside the boundaries of the Constitution,” he said.

Torreon has previously been involved in SC challenges concerning Duterte’s impeachment. In July, he was among petitioners who asked the high court to stop the Senate trial over questions involving Escudero’s authority to preside and the impeachment rules.

The High Court later dismissed as moot the separate petitions filed by Duterte and Torreon challenging the House impeachment proceedings after the Articles of Impeachment were transmitted to the Senate.