Question

2. Cases Not Requiring Preliminary Investigation - Section 1

Francis, a police officer, received information that a certain individual has been frequently selling illegal drugs in his neighborhood. Acting on this information, Francis conducted a surveillance operation and was able to gather substantial evidence of the illegal drug trade being conducted by the said individual. Without conducting a preliminary investigation, Francis immediately filed a criminal complaint before the prosecutor's office charging the individual with illegal drug trafficking.

Will the filing of the criminal complaint by Francis be considered valid despite the absence of a preliminary investigation? Discuss the applicable law and jurisprudence in determining whether a preliminary investigation is necessary in this case.