Manila, Sept. 16 -- Senator-Judge Panfilo Lacson on Wednesday tested whether the Constitution's impeachment vote rule can withstand extraordinary absences its framers may not have foreseen, while raising the possibility that the Senate's eventual interpretation could later be challenged before the Supreme Court.

During questioning of the amici curiae, or friends of the court, Lacson asked retired Associate Justice Adolfo Azcuna to imagine nine of 24 senators becoming stranded abroad by a prolonged war, leaving only 15 available to participate despite all nine retaining their Senate membership.

Azcuna, a member of the 1986 Constitutional Commission, maintained that the denominator would remain 24 and conviction would therefore still requ...