Four convicted crime kingpins are testifying in the congressional inquiry to shed light on the alleged illegal drug trade inside the New Bilibid Prison (NBP).
But just who are these crime lords whose testimonies are awaited by the public and government officials alike?
Sebastian has been described as the top boss in the New Bilibid Prison, where he was transferred in 2009. He was sentenced to life imprisonment for a kidnap-for-ransom case. While inside the prison, he rose from the ranks and became the leader of the Sigue Sigue Sputnik gang.
In previous congressional inquiries, other high-profile inmates said Sebastian made prison gangs sell drugs to beef up the campaign kitty of then Justice Secretary Leila de Lima for the 2016 senatorial elections.
Appearing for the first time before Congress on Monday, he said he personally handed P2 million to De Lima in January 2015, as well as regular "payola" to her alleged bagman, Joenel Sanchez, from March to May of the same year.
He also clarified that he was not a government asset, contrary to De Lima's earlier statement.
Last month, Sebastian was involved in a prison scuffle that resulted in his stabbing and the death of fellow convicted crime lord Tony Co.
De Lima said this may have been the government's way of sending him a message to testify against her. Her critics, on the other hand, implied that she wanted to silence him.
Peter Co a.k.a. Wu Tuan is a convicted drug lord who has been an inmate at the NBP since April 1, 2002.
He was identified by Solicitor General Jose Calida as the one behind the illegal drug trade in Luzon and the National Capital Region.
Co is also reportedly the head of the Bilibid 19, high-profile inmates who were detained by the National Bureau of Investigation in 2014 after contraband were discovered inside their cells.
A sauna, widescreen television sets, wi-fi, split-time aircon units, firearms, cellphones, money-counting machines, laptops, a projector and P1.4 million in cash were found in Co's quarters.
In June, reports surfaced that Co allegedly raised a bounty of P50 million each for President Rodrigo Duterte and Philippine National Police chief Ronald "Bato" dela Rosa.
Co is expected to appear before the House panel investigating the NBP drug trade to testify that he personally handed De Lima drug payoffs.
Vicente Sy is a convicted drug lord who entered the NBP on December 14, 1999.
Also part of the Bilibid 19, he used to be detained in a cell with two airconditioning units.
Sy, together with Sebastian, was also injured in the recent Bilibid stabbing.
A former policeman testified that Sy had an affair with actress Rosanna Roces. She denied the allegation and said that she just supplied him with sex workers.
GERMAN LUNA AGOJO
German Agojo a.k.a. Arman is a convicted drug dealer who has been serving a life sentence since 2002.
He was also tagged in the 2004 killing of Batangas RTC Judge Voltaire Rosales, who convicted him of selling shabu in 1999.
Agojo was among six Bilibid 19 inmates who wrote to the government last June to swear that they were not involved in any plot to have Duterte assassinated.
He suffered a mild stroke last July.