Below is a comprehensive overview of the crimes of adultery and concubinage under Philippine law, with references to the Revised Penal Code (“RPC”) and other related legal principles. This discussion is provided for informational purposes only and should not be construed as legal advice. For specific cases or legal queries, consultation with a qualified attorney is recommended.

1. Legal Framework

The primary legal provisions governing adultery and concubinage in the Philippines are found in the Revised Penal Code (Act No. 3815), specifically:

Article 333 – Adultery
Article 334 – Concubinage

These offenses are categorized as “crimes against chastity” and reflect traditional Filipino legal and moral norms regarding fidelity in marriage.

2. Definitions and Key Elements

2.1. Adultery (Article 333)

Who can commit adultery:
- A married woman, and
- The man who has sexual intercourse with her (knowing that she is married).
Elements:
1. The woman is legally married.
2. There is sexual intercourse between the married woman and a man who is not her husband.
3. The man must know that the woman is married.
Important points:
- Proof of a single act of sexual intercourse is sufficient to bring an adultery charge.
- A woman’s co-accused must be aware of her marital status at the time of the affair, though in practice the courts often presume knowledge if the illicit relationship is public.
- The husband is the only party who can file the criminal complaint for adultery (more on procedural requirements below).

2.2. Concubinage (Article 334)

Who can commit concubinage:
- A married man, and
- The woman (not his wife) who cohabits with him or engages in the specific acts enumerated by law.
Elements:
- The man is legally married.
- He commits any of the following acts:
  1. Keeps a mistress in the conjugal dwelling;
  2. Has sexual intercourse under scandalous circumstances with a woman not his wife;
  3. Cohabits with a woman in any other place (i.e., they set up a home together).
Important points:
- Concubinage involves more than an isolated sexual encounter; it requires either continuous or notorious conduct (e.g., cohabitation or scandalous circumstances).
- The wife is the only party who can file the criminal complaint for concubinage (subject to conditions outlined in Article 344 of the RPC).

3. Penalties

3.1. Penalties for Adultery (Article 333)

The penalty for adultery is prisión correccional in its medium (2 years, 4 months, and 1 day to 4 years and 2 months) to maximum period (4 years, 2 months, and 1 day to 6 years).
Both the married woman and her co-accused (the man) face the same penalty if found guilty.

3.2. Penalties for Concubinage (Article 334)

For the married man:
- The penalty is prisión correccional in its minimum (6 months and 1 day to 2 years and 4 months) to medium period (2 years, 4 months, and 1 day to 4 years and 2 months).
For the concubine (the woman):
- The penalty is destierro, i.e., banishment or prohibition from residing within a certain radius (often around 25 kilometers) of a specified place, usually where the offended party (the wife) resides. This penalty is less severe than the imprisonment penalty for the married man.

These disparate penalties reflect the historical legislative intent that concubinage is considered a “less serious” offense than adultery—though both remain criminal offenses.

4. Who May File the Case and When

4.1. Exclusive Right of the Offended Spouse

Under Article 344 of the Revised Penal Code:

Adultery and concubinage are considered private crimes, meaning only the offended spouse (husband for adultery, wife for concubinage) may file the criminal complaint.
The State generally cannot prosecute these crimes without the explicit participation of the offended spouse.

4.2. Conditions and Procedural Requirements

No condonation or consent
- If it appears that the offended spouse consented to or pardoned the adulterous or concubinous act, a criminal complaint will not prosper.
- Condonation or forgiveness may be implied (e.g., continuing to live together as husband and wife despite knowledge of the affair and explicitly forgiving the act).
Simultaneous filing against both offenders
- For adultery, the offended husband who files a case must include both his wife and her paramour as accused.
- For concubinage, the offended wife who files a case must charge her husband and his concubine together.
- Failure to include both parties in the complaint may result in the dismissal of the case.
Time limit to file
- The complaint for adultery or concubinage must be filed within a certain period from the time the offended spouse becomes aware of the offense; otherwise, it may be barred by prescription (generally 5 years from the date of the commission of the offense, though practical considerations vary).
- It is important to consult legal counsel immediately upon discovering the alleged infidelity.

5. Evidentiary Considerations

5.1. Adultery

Direct evidence (e.g., photographs, witness testimony of the actual sexual act) is rarely obtained, so courts often rely on circumstantial evidence (e.g., witnesses seeing the couple enter a bedroom and remain for a significant time, text messages, social media posts, etc.).
A single act of intercourse can suffice to establish adultery if proven beyond a reasonable doubt.

5.2. Concubinage

More emphasis on proving that the relationship goes beyond a single encounter.
Evidence must show:
- Keeping a mistress in the conjugal dwelling, or
- Scandalous circumstances that cause public embarrassment or knowledge of the affair, or
- Cohabitation in another place, which typically implies setting up a home together.
Documentary evidence (e.g., lease contracts showing both parties reside at the same address), testimony from neighbors, or other circumstantial proof can be used.

6. Common Defenses

Lack of knowledge of the alleged illicit relationship or the marital status of the other party.
Consent or condonation by the offended spouse.
Insufficiency of evidence (e.g., failing to prove beyond a reasonable doubt that sexual intercourse occurred in adultery, or that the elements of cohabitation or scandal are met in concubinage).

7. Effects on Marriage and Other Legal Consequences

7.1. Criminal vs. Civil Remedies

While adultery and concubinage are criminal offenses, they also may serve as grounds in civil or family law proceedings—for example, a petition for legal separation.
However, these offenses do not automatically nullify the marriage; they can be considered as grounds for legal separation or psychological suffering in an annulment/petition for nullity context (though typically annulment in the Philippines requires specific grounds under the Family Code, such as psychological incapacity, fraud, etc.).

7.2. Legal Separation

Adultery or concubinage is among the grounds for legal separation under the Family Code of the Philippines (Executive Order No. 209).
A petition for legal separation based on adultery or concubinage must be filed within five years from the date of discovery of the offense.

7.3. Custody and Support

Courts in custody and support cases consider the “best interest of the child.” Even if a spouse is found guilty of adultery or concubinage, that does not automatically disqualify him or her from getting custody. The decision depends on multiple factors, including the child’s welfare, the moral fitness of the parents, the child’s preferences if they are of age to express them, and overall capability to care for the child.

8. Practical Considerations

8.1. Public Nature of Criminal Proceedings

Filing criminal charges can result in a very public proceeding. Court hearings and records typically become part of the public domain (with some exceptions for sensitive family-related cases), which may have consequences on reputation and privacy for all parties involved.

8.2. Potential for Settlement or Forgiveness

Because adultery and concubinage are private crimes, an offended spouse may choose to drop or no longer pursue the charges, effectively resulting in dismissal (often through an affidavit of desistance).
Even if charges are filed, a subsequent pardon or expressed forgiveness by the offended spouse (before final judgment) can bar or extinguish the criminal action.

8.3. Societal and Cultural Aspects

Although the Revised Penal Code provisions on adultery and concubinage have existed for decades, there are active calls among some lawmakers and advocacy groups to decriminalize these offenses. They argue it perpetuates archaic views on marriage and imposes undue burdens on women.
Nevertheless, as of this writing, adultery and concubinage remain punishable crimes under Philippine law.

9. Conclusion

Adultery and concubinage in the Philippines are distinct criminal offenses punishable under the Revised Penal Code. Adultery applies to a married woman and her paramour, punishable by imprisonment, while concubinage applies to a married man and his concubine, punished with imprisonment for the man and banishment (destierro) for the woman. These crimes can only be prosecuted through a complaint filed by the offended spouse, subject to legal requirements such as non-condonation and simultaneous filing of charges against both guilty parties.

Given the complexities—ranging from evidence requirements and procedural rules to the broader family and social consequences—anyone contemplating filing an adultery or concubinage case should consult with a qualified lawyer. Such legal counsel ensures the correct application of law, better understanding of rights and obligations, and guidance through the intricate processes of the Philippine judicial system.

Disclaimer:
This document provides a general overview based on the Revised Penal Code and related legal provisions in the Philippines. It does not constitute legal advice. Individuals should seek professional legal counsel to address specific concerns or factual scenarios.