A.M. No. 190-RET - IN RE: Chanliongco

On August 2, 2011, the Commission on Elections (COMELEC) issued Resolution No. 9266 approving a joint COMELEC–Department of Justice (DOJ) investigation into alleged fraud in the 2004 and 2007 elections.
On August 15, 2011, the COMELEC and DOJ promulgated Joint Order No. 001-2011 creating:

A Fact-Finding Team (FFT), chaired by an Assistant Secretary of Justice and composed of DOJ, COMELEC, and NBI officials, tasked with gathering evidence and witness affidavits.
A Joint Preliminary Investigation Committee (JPIC), chaired by the DOJ Prosecutor General with additional DOJ and COMELEC members, tasked with conducting preliminary investigations based on FFT reports.

Section 2 of the Joint Order directed the JPIC to recommend resolutions of probable cause for electoral offenses to the COMELEC, while FFT would submit periodic and final reports.

On October 20, 2011, the FFT submitted an Initial Report finding probable fraud in the 2007 senatorial races in North/South Cotabato and Maguindanao and recommending preliminary investigation for several respondents, including petitioners Arroyo, Abalos Sr., and President Arroyo.
Senator Pimentel filed a separate complaint-affidavit for electoral sabotage on October 17, 2011; the JPIC consolidated both matters and issued subpoenas.
Petitioners filed Rule 65 petitions for certiorari and prohibition in the Supreme Court challenging:

The COMELEC en banc on November 18, 2011 approved the JPIC’s recommendation with modifications and ordered the filing of informations for electoral sabotage in the Pasay RTC.

Three petitions were consolidated: G.R. No. 199082 (Mike Arroyo), G.R. No. 199085 (Benigno Abalos Sr.), and G.R. No. 199118 (President Arroyo).
Petitioners sought TROs and injunctions to enjoin the JPIC proceedings. The Supreme Court required briefs, held oral argument, and deferred TRO resolution.

Does it violate the due process clause by fusing investigative and adjudicative functions?
Does it violate the equal protection clause by targeting only 2004 and 2007 elections?
Does it transgress the principle of separation of powers by creating a quasi-new office?
Does it undermine the COMELEC’s constitutional independence by aligning it with the DOJ?

Can the COMELEC validly conduct preliminary investigations jointly with the DOJ under existing statutes?
Were petitioners afforded the opportunity to be heard and to inspect evidence under Rule 112, Rules on Criminal Procedure, and COMELEC Rules of Procedure?