For Senate Minority Leader Aquilino "Koko" Pimentel III, a parallel investigation in the Senate on the previous Duterte administration's drug war is a "good idea".

Pimentel said in a text message on Tuesday, Oct. 15, that while this was "optional", it was a good idea to him "because it will give us the opportunity to ask cross-examination questions to test the credibility of the witnesses".

It was Senator Christopher Lawrence "Bong" Go who brought up the possibility of the Senate conducting a parallel probe of former president Rodrigo Duterte's drug war, alongside that of the House quad-committee (quad-comm).

"Kung kakailanganin po para magkaroon tayo ng parallel investigation dito sa Senado para malaman po natin ang katotohanan (If it's necessary so we can have a parallel investigation here in the Senate so we can find out the truth)," he said.

"I'm very much willing na mag-file din po ng resolusyon para magkaroon po ng investigation rin po dito sa Senado. Para malaman natin kung ano lang yung totoo (I'm very much willing to file a resolution for an investigation to be conducted in the Senate as well. So we can find out what the truth really is)," Go added.

Recently, retired police colonel and former Philippine Charity Sweepstakes Office (PCSO) general manager Royina Garma mentioned Go's involvement in the so-called "Davao model", which allegedly entails a cash reward system that encourages the killing of drug suspects.

Garma claimed this would later be adopted by Duterte on a national scale, based on her affidavit.

Go has reiterated that he had nothing to do with Duterte's war on drugs.

Asked which committee should lead the Senate investigation, Pimentel said that it would depend on where Senate President Francis "Chiz" Escudero and the plenary would refer the resolution.

He added that the Senate might summon new witnesses to the hearing if it pushes through.