EXPLAINER: What is a quorum and its impact on Senate, House proceedings?

With Senate President Alan Peter Cayetano pushing for a vote on whether to take up Sen. Rodante Marcoleta’s proposed rule amendment to allow senators to participate in proceedings online, Senate Minority Leader Vicente “Tito” Sotto III rose and moved for a quorum call.

Faced with the nearly impossible task of winning the vote because of the majority’s slim edge in numbers, the other members of the minority, after vehement objections, walked out of the plenary, leaving their leader, Sotto, to question the quorum and move for an adjournment.

Without the members of the minority to constitute the quorum, Cayetano didn’t object to the motion to adjourn by Sotto, the former Senate President, a five-term senator, and several times the majority leader and chairman of the Committee on Rules.

Former Sen. Franklin Drilon, who’s also a former Senate President and former majority leader, summed up the power and the concept of quorum in a text message to GMA News.

“Leaving the session hall to force an adjournment (due to lack of a quorum) is a parliamentary practice that is resorted to in order to prevent the approval of a measure,” Drilon said.

Sotto himself remembers other instances when senators walked out of the session hall.

"Yes, a number of times. During the time of Avelino and my grandpa. Then, during the time of Salonga. Then kami nina Nene," Sotto said in a text message.

Sotto is the grandson of Sen. Vicente Sotto, who was a colleague of Sen. Jose Avelino. He was also referring to former Senate Presidents Jovito Salonga and Aquilino "Nene" Pimentel.

What constitutes a quorum in a legislative body like the Senate?

Rule XV Section 44 of the Senate Rules defines quorum as a majority of the senators, “and, in its absence, a smaller number may adjourn from day to day and may compel the attendance of absent members in the manner provided in Section 99 hereof.”

In the case of the 24-member Senate, a quorum would need 13 members present in the session hall.

The Senate majority is now made up of exactly 13 members. They are:

1. Alan Cayetano
2. Pia Cayetano
3. Bong Go
4. Bato dela Rosa
5. Chiz Escudero
6. Jinggoy Estrada
7. Loren Legarda
8. Rodante Marcoleta
9. Imee Marcos
10. Robin Padilla
11. Joel Villanueva
12. Camille Villar
13. Mark Villar

Dela Rosa was taken into protective custody by the Senate, but left the premises hours after the Senate shooting incident on May 13. He is the subject of a warrant of arrest issued by the International Criminal Court in connection with the deaths in the Duterte administration's war on drugs.

As Sotto said towards the end of the session on Tuesday, Section 45 of the Senate Rules provides, “Should the question of lack of quorum be raised, the Chair, without debate, shall immediately proceed to a verification thereof by causing the reading of the roll of the Senators and announcing forthwith the result.”

Without a quorum, Section 99 states, “the lack of quorum shall compel the President to adjourn the session, unless, by means of motion, which shall not be subject to debate, a majority of the Senators present agree to its suspension and ask the President or Presiding Officer to order the Sergeant-at-Arms to require the appearance of the absent members or, if it is deemed necessary, to order their arrest so as to form the necessary quorum.”

On Tuesday night, there was no agreement among the senators still present in the session hall to order the Sergeant-at-Arms to require the appearance of the “absent members.”

One instance when the lack of a quorum derailed the passage of an important measure was on June 4, 2010.

Some shouted in protest while others shed tears as they all watched the House of Representatives adjourn its session without acting on a freedom of information bill that could have been ratified in minutes.

With only 128 out of 268 members present, the House failed to ratify the reconciled version of the measure that would have increased government transparency by allowing citizens easier access to government documents and data, and imposing penalties for denying the right.

The Senate ratified the measure four months before. At least 135 House members were needed to constitute a quorum and enable the chamber to tackle legislative matters. –with reports from Sandra Aguinaldo/NB, GMA News