"x x x.
The Secretary of Justice has the discretion, upon motion or motu proprio, to act on any matter that may cause a probable miscarriage of justice in the conduct of a preliminary investigation. This action may include, but is not limited to, the conduct of a reinvestigation.
Furthermore, a petition for certiorari under Rule 65 questioning the regularity of preliminary investigation becomes moot after the trial court completes its determination of probable cause and issues a warrant of arrest.
x x x."