G.R. No. 125865 - Liang vs. People

Petitioner: Jeffrey Liang (Huefeng), an economist employed by the Asian Development Bank (ADB).
Respondent: People of the Philippines, represented by the Office of the Solicitor General.

In 1994, petitioner was charged before the Metropolitan Trial Court (MeTC) of Mandaluyong City with two counts of grave oral defamation for allegedly uttering defamatory words against a fellow ADB worker, Joyce Cabal.
MeTC issued a warrant of arrest; petitioner posted bail of ₱2,400 per charge and was released to the custody of the ADB Security Officer.
The next day, the MeTC received an ex parte “office protocol” from the Department of Foreign Affairs (DFA) asserting that petitioner enjoyed immunity from legal process under Section 45 of the Agreement between the ADB and the Philippine Government.
Relying solely on the DFA communication, the MeTC judge motu proprio dismissed both criminal cases without notifying the prosecution.
The prosecution filed a motion for reconsideration in the MeTC, which the DFA opposed; the motion was denied.
The prosecution then petitioned the Regional Trial Court (RTC) of Pasig City for certiorari and mandamus; the RTC set aside the MeTC dismissal and ordered enforcement of the original warrant of arrest.
Petitioner elevated the matter to the Supreme Court by petition for review, contending (a) that he was immune from suit under the ADB Agreement, and (b) that no preliminary investigation preceded the filing of the criminal cases.

Whether the DFA’s ex parte protocol communication confers binding immunity on the petitioner and whether the MeTC violated the prosecution’s right to due process by dismissing the cases without notice.

Whether immunity under Section 45(a) of the ADB Agreement is absolute or limited to acts performed in the official capacity of ADB officers and staff.

Whether the crime of grave oral defamation can fall within the “official acts” exempted from legal process under the ADB Agreement.

Whether a preliminary investigation is required in MeTC-cognizable cases such as grave oral defamation.