What Is Preliminary Investigation in the Philippines?
A preliminary investigation is a critical stage in Philippine criminal procedure. It is the process conducted by a prosecutor to determine whether a criminal case should be filed in court. Contrary to popular belief, it is not a trial and does not decide guilt or innocence. Instead, it acts as a legal filter to ensure that only cases supported by sufficient evidence proceed to trial.
Understanding what a preliminary investigation is, and what it is not, is essential for both complainants and respondents in criminal cases.
Legal Definition of Preliminary Investigation
Under Rule 112 of the Rules of Criminal Procedure, a preliminary investigation is defined as an inquiry to determine whether there is sufficient ground to believe that:
A crime cognizable by the Regional Trial Court (RTC) has been committed; and
The respondent is probably guilty and should be held for trial.
Philippine jurisprudence consistently characterizes preliminary investigation as inquisitorial and summary in nature. This means the prosecutor’s role is to evaluate evidence submitted by the parties, not to conduct a full-blown adversarial proceeding.
Updated Quantum of Evidence: Reasonable Certainty of Conviction
Traditionally, preliminary investigation was associated with the concept of probable cause. However, under the 2024 DOJ–NPS Rules, the standard has evolved.
Today, prosecutors are required to determine whether the evidence on record establishes prima facie evidence showing reasonable certainty of conviction, not merely suspicion or possibility.
In practical terms, this means:
The evidence must be credible, coherent, and sufficient, if left unrebutted, to support a conviction in court.
Mere allegations, uncorroborated claims, or speculative assertions are no longer enough.
The prosecutor must assess whether the case has a realistic chance of resulting in a conviction, not just whether a crime might have occurred.
This heightened standard strengthens due process protections and reduces the filing of weak or harassment cases.
Purpose of a Preliminary Investigation
A preliminary investigation serves two equally important purposes:
1. Protection of the Accused
It shields individuals from hasty, malicious, or unfounded prosecutions. No person should be forced to undergo the stress, expense, and stigma of a criminal trial without sufficient legal basis.
2. Protection of the State
It prevents the government from wasting resources on cases that are unlikely to succeed, ensuring that courts are not clogged with prosecutions lacking evidentiary support.
Because of these objectives, courts generally refrain from interfering with prosecutorial discretion, absent grave abuse.
Nature of the Proceedings: What It Is—and What It Is Not
A preliminary investigation has distinct characteristics:
Not a trial on the merits – There is no determination of guilt beyond reasonable doubt.
Summary and non-adversarial – The prosecutor may rely on affidavits, counter-affidavits, and documentary evidence.
Technical rules of evidence do not strictly apply – Issues of admissibility and weight of evidence are generally matters for trial.
As emphasized in jurisprudence, objections that go into the credibility of witnesses or the admissibility of evidence are usually resolved during trial, not during preliminary investigation.
How a Preliminary Investigation Is Conducted
While procedures may vary slightly depending on the offense and the office handling the case, the general steps are:
Filing of the complaint-affidavit by the complainant, with supporting evidence.
Issuance of a subpoena to the respondent, directing the filing of a counter-affidavit.
Submission of reply and rejoinder affidavits, if allowed.
Evaluation of evidence by the prosecutor.
Issuance of a resolution either dismissing the complaint or finding sufficient basis to file an Information in court.
Throughout this process, the prosecutor’s task is to determine whether the evidence meets the standard of reasonable certainty of conviction.
Why Preliminary Investigation Matters
For complainants, a strong preliminary investigation ensures that the case filed in court is well-founded and defensible. For respondents, it is a crucial opportunity to stop a weak or defective case before it reaches trial.
Because errors at this stage can have serious consequences, resolutions issued in preliminary investigations may be challenged through motions for reconsideration, petitions for review, or, in exceptional cases, petitions alleging grave abuse of discretion.
Conclusion
A preliminary investigation is a gatekeeping mechanism in Philippine criminal justice. It is a summary prosecutorial inquiry designed to determine whether a criminal case deserves to proceed to court—not whether the accused is guilty.
Under current rules, the prosecutor must find prima facie evidence showing reasonable certainty of conviction, not mere suspicion or possibility. This higher standard reinforces constitutional due process, protects individuals from baseless prosecutions, and promotes a more efficient and credible justice system.
If you are involved in a criminal complaint—whether as complainant or respondent—understanding the nature and purpose of preliminary investigation is essential to protecting your rights and interests.
*This blog post is intended for informational and academic purposes only and does not constitute legal advice. Readers are encouraged to consult a qualified lawyer for advice specific to their individual circumstances.
Need a lawyer for your preliminary investigation?
Contact us and set an appointment today. Our team is ready to guide you through every step with clarity, compassion, and legal precision.
