Introduction

In the Philippines, marital infidelity is not merely a personal betrayal but a criminal offense under the Revised Penal Code (RPC). The crimes of adultery and concubinage address acts of unfaithfulness in marriage, reflecting the country's strong emphasis on family values and the sanctity of marriage as enshrined in the 1987 Constitution and the Family Code. These offenses are distinct, with adultery applying primarily to married women and their paramours, while concubinage pertains to married men and their mistresses. This article provides a comprehensive overview of these crimes, including their legal definitions, elements, penalties, evidentiary requirements, and the step-by-step process for filing a case against a cheating spouse and any involved third party. It is grounded in Philippine jurisprudence and statutory law, such as Republic Act No. 3815 (the RPC) and relevant Supreme Court decisions.

While these laws criminalize infidelity, they have faced criticism for gender bias, as adultery is easier to prove and carries harsher penalties than concubinage. Efforts to reform or repeal these provisions have been ongoing, but as of the current legal framework, they remain enforceable. Victims—typically the offended spouse—can pursue these cases to seek justice, though success depends on strong evidence and adherence to procedural rules.

Legal Definitions and Distinctions

Adultery (Article 333, RPC)

Adultery is committed by a married woman who engages in sexual intercourse with a man who is not her husband. The man involved, if aware of her marital status, is also criminally liable as a co-principal. This offense is consummated by a single act of sexual intercourse, regardless of whether it occurs in private or public.

Key points:

It applies exclusively to the wife and her paramour.
The husband cannot be charged with adultery; his infidelity falls under concubinage.
The crime is based on the act itself, not on emotional or financial aspects.

Concubinage (Article 334, RPC)

Concubinage is committed by a married man in one of three ways:

Keeping a mistress in the conjugal dwelling.
Having sexual intercourse with a woman (not his wife) under scandalous circumstances.
Cohabiting with her in any other place.

The woman involved, if she knows the man is married, is also liable as a co-principal. Unlike adultery, concubinage requires more than a single act—it often involves ongoing cohabitation or public scandal.

Distinctions between adultery and concubinage:

Gender specificity: Adultery targets wives, concubinage targets husbands.
Proof threshold: Adultery is proven by one act of intercourse; concubinage needs evidence of cohabitation, scandal, or habitation in the family home.
Rationale: Rooted in historical patriarchal norms, where a wife's infidelity was seen as more threatening to lineage and family honor.

These crimes do not apply to same-sex infidelity or non-marital relationships, as they presuppose a valid marriage. Annulled or void marriages may negate liability, depending on the circumstances.

Elements of the Crimes

To establish guilt, the prosecution must prove the following elements beyond reasonable doubt:

For Adultery:

The woman is married (a valid, subsisting marriage).
She engages in sexual intercourse with a man not her husband.
The man knows she is married (for his liability).

For Concubinage:

The man is married.
He commits one of the three acts: (a) keeps a mistress in the conjugal home; (b) has sexual intercourse under scandalous circumstances; (c) cohabits elsewhere.
The woman knows he is married (for her liability).

"Scandalous circumstances" refer to acts that offend public decency, such as open displays of affection or living together notoriously. "Cohabitation" implies more than occasional meetings—it suggests a semi-permanent living arrangement.

In both cases, the offended spouse must be the complainant, as these are private crimes under Article 344 of the RPC. Only the aggrieved husband (for adultery) or wife (for concubinage) can initiate the case, unless they are incompetent or deceased, in which case ascendants, descendants, or guardians may step in.

Penalties and Consequences

Penalties

Adultery: Prisión correccional in its medium and maximum periods (2 years, 4 months, and 1 day to 6 years). Both the wife and paramour face the same penalty.
Concubinage: Prisión correccional in its minimum and medium periods (6 months and 1 day to 4 years and 2 months) for the husband; destierro (banishment) for the mistress.

If aggravating circumstances exist (e.g., abuse of authority), penalties may increase. Mitigating factors, like voluntary surrender, can reduce them.

Additional Consequences

Civil implications: Conviction can support grounds for legal separation under Article 55 of the Family Code (sexual infidelity). It may also affect child custody, property division, and support obligations.
Pardon and prescription: The offended spouse can pardon the offenders before trial, extinguishing the case (Article 344, RPC). The crime prescribes after 10 years from discovery (Article 90, RPC).
Impact on marriage: These cases do not automatically dissolve the marriage; annulment or declaration of nullity must be sought separately.
RA 9262 overlap: If infidelity involves violence or economic abuse, it may fall under the Anti-Violence Against Women and Their Children Act, providing additional remedies like protection orders.

Supreme Court rulings, such as in People v. Zapata (G.R. No. L-30441, 1971), emphasize that moral certainty of guilt is required, and mere suspicion is insufficient.

Evidence and Proof

Proving these crimes is challenging due to their private nature. Common evidence includes:

Direct evidence: Witness testimonies to acts of intercourse or cohabitation (rarely available).
Circumstantial evidence: Hotel records, text messages, photos, videos, bank statements showing shared expenses, or social media posts indicating scandal.
Confessions: Admissions by the accused, but these must be voluntary and corroborated.
Expert testimony: DNA tests for paternity in related child support claims, or forensic analysis of digital evidence.

The "equipoise rule" applies: if evidence is evenly balanced, the accused is acquitted. In People v. Serrano (G.R. No. 179038, 2010), the Court acquitted due to lack of proof of knowledge of marriage.

Defenses may include:

Invalid marriage (e.g., bigamy).
Lack of knowledge of marital status.
Absence of sexual intercourse or scandal.
Pardon by the offended spouse.

How to File a Case: Step-by-Step Guide

Filing a case for adultery or concubinage is a criminal process initiated via complaint, not a civil suit. It falls under the jurisdiction of the Municipal Trial Court (MTC) or Regional Trial Court (RTC), depending on the penalty.

Step 1: Gather Evidence

Collect all possible proof discreetly to avoid alerting the accused, which could lead to evidence destruction. Consult a lawyer to assess strength of case.

Step 2: File a Complaint-Affidavit

Prepare a sworn complaint-affidavit detailing the facts, elements, and evidence.
Submit it to the Office of the City or Provincial Prosecutor (Fiscal) in the place where the crime occurred or where the accused resides.
Include witnesses' affidavits if available.
Pay minimal filing fees (around PHP 500–1,000, subject to adjustment).

The prosecutor conducts a preliminary investigation to determine probable cause.

Step 3: Preliminary Investigation

The accused is subpoenaed to submit a counter-affidavit.
The prosecutor may hold clarificatory hearings.
If probable cause is found, the case is endorsed to court via an information (charging document).
If dismissed, the complainant can appeal to the Department of Justice.

Step 4: Court Proceedings

Arraignment: Accused pleads guilty or not guilty.
Pre-trial: Possible plea bargaining or mediation (though rare for these crimes).
Trial: Presentation of evidence, cross-examination.
Judgment: Conviction or acquittal.

Step 5: Post-Judgment

Appeal to the Court of Appeals if convicted.
Execution of sentence upon finality.

Timeline: Preliminary investigation takes 1–3 months; trial can last 1–5 years due to court backlog.

Involving the Third Party

The paramour or mistress is charged as a co-accused. The complaint must allege their knowledge of the marriage. If evidence is insufficient against them, the case against the spouse may still proceed.

Challenges and Considerations

Gender inequality: Critics argue the laws are discriminatory, violating equal protection under the Constitution. Bills like House Bill No. 100 (Decriminalizing Adultery and Concubinage) have been proposed but not passed.
Privacy concerns: Gathering evidence may involve surveillance, risking violations of RA 10173 (Data Privacy Act) or RA 9995 (Anti-Photo and Video Voyeurism Act).
Emotional toll: These cases often exacerbate family conflicts, affecting children.
Alternatives: Instead of criminal charges, consider counseling, legal separation, or annulment for a less adversarial resolution.
Bigamy overlap: If the infidelity involves a second marriage, it may constitute bigamy (Article 349, RPC), a separate crime with harsher penalties.

Jurisprudence Highlights

People v. Nepomuceno (G.R. No. L-40624, 1976): Clarified that "scandalous circumstances" require public notoriety.
Ligtas v. People (G.R. No. 200751, 2015): Emphasized the need for direct or strong circumstantial evidence of intercourse.
Garcia v. Drilon (G.R. No. 179267, 2013): While on VAWC, it underscores protections for spouses in abusive infidelity scenarios.

These cases illustrate the judiciary's strict evidentiary standards to prevent abuse of these laws for harassment.

Conclusion

Adultery and concubinage remain potent legal tools for addressing marital infidelity in the Philippines, balancing family protection with criminal accountability. However, pursuing such cases requires careful preparation, robust evidence, and awareness of their emotional and legal complexities. Victims should seek professional legal advice to navigate this process effectively, ensuring compliance with procedural safeguards and maximizing chances of success.