In the Philippines, marriage is a sacred social institution protected by the Constitution and reinforced by both criminal and civil laws. Unlike many jurisdictions that have decriminalized infidelity, the country retains the crimes of adultery and concubinage under the Revised Penal Code (RPC). These offenses directly answer the question: yes, a spouse can be imprisoned upon conviction, provided the elements of the crime are proven beyond reasonable doubt and a proper criminal complaint is filed by the offended spouse. These provisions fall under Title XI, Book Two of the RPC as crimes against chastity and reflect the legal system’s emphasis on marital fidelity, influenced by the nation’s cultural and religious traditions.

Legal Basis
Adultery is defined under Article 333 of the RPC, while concubinage is defined under Article 334. Both crimes apply exclusively to spouses in a valid and subsisting marriage recognized under Philippine law. The offenses do not attach if the marriage is later declared void ab initio, but acts committed while the marriage was presumed valid remain prosecutable if all other elements are met. These are classified as private crimes under Article 344 of the RPC, meaning they cannot be initiated by police, prosecutors, or third parties on their own.

Adultery
Article 333 provides that adultery is committed by any married woman who shall have sexual intercourse with any man not her husband, and by the man who has carnal knowledge of her, knowing that she is married, even if the marriage be subsequently declared void.

The elements are:

The woman is married.
She engages in sexual intercourse with a man who is not her husband.
The man has carnal knowledge of her with knowledge of her married status.

Liability extends to both the wife and her paramour. The husband cannot be charged with adultery for his own extramarital acts; he is instead subject to the rules on concubinage.

Concubinage
Article 334 states that concubinage is committed by any husband who shall:

Keep a mistress in the conjugal dwelling;
Have sexual intercourse, under scandalous circumstances, with a woman who is not his wife; or
Cohabit with her in any other place.

The concubine (mistress) is also criminally liable. The elements vary by mode but center on the husband’s maintenance of an extramarital relationship that offends marital fidelity, either through cohabitation, scandal, or habitual keeping of a mistress.

Penalties and Imprisonment
Conviction for either offense carries penalties involving imprisonment, confirming that a spouse (and the third party) can indeed be sent to jail.

Adultery: The wife and the paramour each face prision correccional in its medium and maximum periods — two years, four months and one day to six years.
Concubinage: The husband faces prision correccional in its minimum and medium periods — six months and one day to four years and two months. The concubine faces prision correccional in its minimum period — six months and one day to two years and four months.

These are afflictive penalties that entail actual incarceration upon final conviction, subject to the rules on probation for qualified first-time offenders or suspension of sentence where applicable. Accessory penalties may include disqualification from holding public office or parental authority, and civil liabilities such as moral and exemplary damages can also be awarded.

Prosecution as a Private Crime
Because adultery and concubinage are private crimes, only the offended spouse may file the criminal complaint. Article 344 requires that the complaint:

Be filed in writing and under oath;
Include both the guilty spouse and the third party (paramour or concubine), if known and alive;
Be filed before the proper prosecutor or court with jurisdiction over the place where the offense occurred.

The action cannot proceed if the offended spouse has consented to the act or has pardoned the offenders. Pardon may be express (made before the filing of the complaint) or implied (for example, by continuing to live together as husband and wife after acquiring knowledge of the offense). If the offended spouse is a minor or incapacitated, the parents, grandparents, or guardians may file on their behalf.

The criminal action prescribes in ten years under the general rules for offenses punishable by correctional penalties. Discovery of the offense generally starts the running of the period, though courts examine the facts of each case.

Defenses and Extinguishment of Criminal Liability
Common defenses include:

Absence of any essential element (e.g., lack of proof of sexual intercourse, lack of knowledge by the paramour that the woman was married, or absence of scandal/cohabitation in concubinage).
Express or implied pardon by the offended spouse.
Prescription of the action.
Invalidity of the marriage at the time of the act (in certain cases).
Insufficiency of evidence, alibi, or denial supported by corroboration.

Once criminal liability is extinguished by pardon or prescription, the case is dismissed. Conviction requires proof beyond reasonable doubt, often established through direct evidence (witnesses, admissions) or strong circumstantial evidence (hotel records, communications, or observed cohabitation).

Relation to Family Code and Civil Consequences
While criminal in nature, adultery and concubinage also serve as grounds for legal separation under Article 55 of the Family Code of the Philippines. They may support findings of psychological incapacity for annulment or nullity of marriage under Article 36. A criminal conviction strengthens civil actions involving:

Separation of property;
Child custody and support;
Forfeiture of share in conjugal or absolute community property;
Termination of parental authority in extreme cases.

Because the Philippines does not have a general divorce law (except for Muslim Filipinos under Presidential Decree No. 1083, which contains parallel provisions on adultery and concubinage), legal separation remains the primary civil remedy. Criminal cases are sometimes filed strategically to gain leverage in family court proceedings.

Gender Asymmetry and Constitutional Considerations
The law draws a clear distinction between spouses. A wife can be convicted of adultery upon proof of a single act of sexual intercourse. A husband, however, must satisfy one of the three specific modes of concubinage, which generally require more sustained or public conduct. This disparity has been criticized as reflecting outdated views on fidelity and paternity concerns, yet the Supreme Court has consistently upheld the provisions as a valid exercise of legislative power rooted in traditional family policy.

Practical Enforcement and Current Legal Landscape
Although imprisonment is legally possible and has occurred in prosecuted cases, actual convictions leading to jail time are relatively rare. Many couples prefer reconciliation, legal separation, or annulment over the lengthy and stigmatizing criminal process. Criminal complaints are often used as bargaining tools in marital disputes rather than pursued to final judgment. Bail is generally available, as the offenses are not classified as non-bailable. Evidence requirements are stringent, and courts demand clear and convincing proof of the sexual acts or cohabitation.

The provisions remain fully in force under the RPC. Proposals to decriminalize or amend the law have been discussed in Congress over the years, but no repeal or significant revision has been enacted. For Muslim Filipinos, the Code of Muslim Personal Laws provides its own framework, which may impose different penalties but similarly recognizes the criminality of such acts within valid marriages.

In sum, Philippine law permits the imprisonment of a spouse for adultery or concubinage when the statutory elements are established, the offended spouse initiates the private criminal action, and no pardon or prescription bars the case. The offenses carry both criminal and far-reaching civil repercussions within the family law regime, underscoring the legal system’s protection of marital fidelity.