Under the Revised Penal Code of the Philippines (RPC), adultery and concubinage are classified as crimes against chastity. These are private crimes that can only be prosecuted upon the complaint of the offended spouse. The legal framework is found in Articles 333 and 334 of the RPC, which remain in force and are supplemented by procedural rules under the Rules of Court, the Family Code (particularly as a ground for legal separation), and relevant jurisprudence. Filing a criminal case requires not only the proper complainant but also sufficient evidence to establish probable cause during preliminary investigation and, ultimately, guilt beyond reasonable doubt at trial. This article exhaustively examines the elements of each offense, the procedural requirements, the prescriptive period, the doctrine of pardon and condonation, the specific evidence needed, forms of admissible proof, common challenges, available defenses, penalties, and related civil remedies.

Legal Definitions and Elements

Adultery (Article 333, RPC)
Adultery is committed by (1) any married woman who has sexual intercourse with a man who is not her husband, and (2) the man who has carnal knowledge of her, knowing that she is married.

The elements are:

The woman is legally married (subsisting valid marriage at the time of the act).
She engaged in sexual intercourse with a man other than her husband.
The man had carnal knowledge of her.
The man knew, at the time of the act, that the woman was married.

Only a single act of sexual intercourse is required. The offense is gender-specific: a married man cannot commit adultery; his equivalent act falls under concubinage.

Concubinage (Article 334, RPC)
Concubinage is committed by any husband who:
(a) keeps a mistress in the conjugal dwelling;
(b) has sexual intercourse with a woman who is not his wife under scandalous circumstances; or
(c) cohabits with such woman in any other place.

The concubine (the woman involved) is also liable and suffers the penalty of destierro.

The elements are:

The man is legally married.
He maintains a mistress or engages in the prohibited acts with a woman who is not his wife.
For variant (a): the mistress resides in the conjugal home.
For variant (b): the sexual act occurs under circumstances that cause public scandal (known or ought to be known in the community).
For variant (c): the couple lives together as husband and wife in any other place (even without public scandal).

Unlike adultery, concubinage generally requires a pattern of conduct rather than a single act, except where the single act is scandalous.

Key Distinctions Between Adultery and Concubinage

Gender bias: Only a wife (and her paramour) can commit adultery; only a husband (and his concubine) can commit concubinage.
Number of acts: Adultery needs one act; concubinage typically needs continuity or scandal.
Penalty asymmetry: The husband in concubinage receives prision correccional in its medium and maximum periods (same as adultery), while the concubine receives only destierro (banishment from 6 months and 1 day to 6 years).
Proof threshold: Concubinage variants (b) and (c) demand additional proof of scandal or cohabitation.

Who May Initiate the Case

Only the offended spouse may file the complaint (Article 344, RPC). Parents, children, or third parties have no legal personality to institute the action, even if they have personal knowledge of the infidelity. If the offended spouse is a minor, insane, or absent, the parents or guardians may file in his/her behalf. The complaint must be signed and sworn to by the offended spouse personally before a prosecutor or notary public. If both spouses are guilty of their respective offenses, mutual pardon is possible.

Procedure for Filing the Case

The offended spouse executes a complaint-affidavit detailing the facts and attaching supporting evidence.
The affidavit is filed with the Office of the City or Provincial Prosecutor (or directly with the Municipal Trial Court in limited cases) having territorial jurisdiction over the place where the offense was committed or where the offended spouse resides.
Preliminary investigation is conducted to determine probable cause. The respondents (spouse and paramour/concubine) are given an opportunity to submit counter-affidavits.
If probable cause is found, an Information is filed in the proper court—usually the Municipal Trial Court (MTC) or Metropolitan Trial Court (MeTC) because the penalty does not exceed six years.
Arraignment, pre-trial, trial on the merits, and judgment follow ordinary criminal procedure. Bail is a matter of right.

Prescriptive Period

The offenses prescribe in ten (10) years from the date of commission (Article 90, RPC, since the penalty is correctional). Computation begins from the day the crime was committed. There is no statutory one-year limit tied to discovery; inaction after knowledge, however, may constitute implied pardon or condonation, which extinguishes criminal liability.

Pardon and Condonation

Express pardon must be made in writing and filed in court before the prosecution presents evidence. Implied pardon (condonation) arises when the offended spouse continues to live with the guilty spouse as husband and wife after gaining knowledge of the offense, or resumes sexual relations, or fails to act for an extended period despite knowledge. Once granted, pardon is irrevocable and bars prosecution or causes dismissal even after an Information has been filed. Reconciliation during the pendency of the case often leads to withdrawal of the complaint and dismissal.

Evidence Required: General Principles

To establish probable cause at the preliminary investigation and guilt beyond reasonable doubt at trial, the prosecution must prove every element of the offense. Direct evidence of the sexual act itself is rarely available; courts routinely convict on circumstantial evidence provided the circumstances form an unbroken chain that leads to the reasonable and moral certainty that the crime was committed. The quantum of evidence is the same as in any criminal case: proof beyond reasonable doubt. The marriage must be proved by a valid marriage certificate (or secondary evidence if lost). Knowledge of the marital status by the paramour/concubine must also be established.

Specific Evidence for Adultery

Proof of marriage: Certified true copy of the marriage contract from the Philippine Statistics Authority (PSA) or the solemnizing officer’s record.
Proof of sexual intercourse:
– Hotel or motel registration records showing the wife and the paramour registered as “Mr. and Mrs.” or stayed overnight together.
– CCTV footage or time-stamped photos of the couple entering and leaving a hotel/motel together and not emerging for hours.
– Witness testimonies (hotel staff, security guards, neighbors, or private investigators) who saw the couple in a compromising situation.
– Text messages, chat logs (Viber, Messenger, WhatsApp), emails, or letters containing admissions of sexual relations or explicit content.
– Photographs or videos showing the couple in intimate acts or in bed together.
– Birth of a child during the marriage with DNA evidence proving the biological father is not the husband.
– Love letters, gifts, or financial records showing the paramour supporting the wife.

A single overnight stay in a motel coupled with registration as husband and wife has been held sufficient by courts when corroborated by other circumstances.

Specific Evidence for Concubinage

Proof of marriage: Same as above.
For keeping a mistress in the conjugal dwelling:
– Testimony of household help, neighbors, or relatives that the mistress resides in the family home.
– Photographs or videos inside the conjugal dwelling showing the mistress’s personal belongings, clothes, or sleeping arrangements.
– Utility bills or lease contracts in the mistress’s name at the conjugal address.
For sexual intercourse under scandalous circumstances:
– Multiple witnesses (neighbors, friends, relatives) who saw the couple kissing, holding hands, or behaving as husband and wife in public.
– Social media posts tagging the couple together with captions implying intimacy.
– Repeated hotel stays or public displays witnessed by the community.
For cohabitation in any other place:
– Lease contract, barangay certificate, or utility bills showing the husband and the woman living together at a separate address.
– Testimony that they hold themselves out as husband and wife (introducing each other as such, joint bank accounts, shared child).
– Photographs or videos of the couple living together.

The scandalous-circumstances variant requires proof that the act caused public embarrassment or was notorious in the locality.

Admissible Forms of Evidence

Documentary: Marriage certificate, hotel receipts, text printouts (authenticated), birth certificates, DNA laboratory reports, barangay certificates of cohabitation.
Testimonial: Affidavits and court testimony of eyewitnesses, private investigators, barangay officials, and family members.
Object/Real: Photographs, videos, used condoms (with proper chain of custody), clothing, or personal items found together.
Electronic: Text messages, emails, social media screenshots (must be authenticated under the Rules on Electronic Evidence).
Scientific: DNA paternity testing (admissible if properly conducted).

All evidence must be relevant, competent, and obtained without violating constitutional rights (e.g., no illegal searches).

Challenges in Proving the Case

Secrecy of the affair makes direct evidence scarce.
Denial by respondents and lack of eyewitnesses to the actual sexual act.
Destruction or deletion of digital evidence.
Cultural stigma that discourages the offended spouse from coming forward.
Difficulty proving the paramour’s/concubine’s knowledge of the marriage.
Risk of counter-charges for illegal wiretapping or violation of the Anti-Photo and Video Voyeurism Act if evidence was obtained improperly.

Defenses Available

Denial and alibi.
Lack of knowledge that the woman was married (for the paramour).
Express or implied pardon/condonation.
Prescription of the offense.
Invalid marriage (bigamy, nullity).
Insanity or minority of the accused at the time of the act.
Entrapment (rarely successful).
Lack of probable cause at preliminary investigation.

Penalties and Consequences upon Conviction

Adultery and concubinage (husband): prision correccional medium and maximum periods (2 years, 4 months and 1 day to 6 years).
Concubine: destierro.
Conviction carries civil interdiction, perpetual disqualification from public office if applicable, and serves as absolute ground for legal separation under Article 55 of the Family Code. It may also affect custody, support, and visitation rights in family proceedings.

Related Civil Remedies

The same set of evidence can support:

Petition for legal separation (absolute divorce not available).
Action for damages (moral and exemplary) under Article 21 of the Civil Code.
Petition for nullity of marriage if fraud or other grounds exist.
Criminal complaints for other offenses (e.g., unjust vexation, grave coercion, or RA 9262 if violence is involved).

The evidence threshold for civil cases is only preponderance of evidence, making parallel civil actions easier to win even if the criminal case is dismissed.

In summary, successfully filing and prosecuting a case for adultery or concubinage demands meticulous documentation of the marital relationship and the illicit affair through a combination of documentary, testimonial, and circumstantial proof. The offended spouse must act personally and without condonation. Every element must be established with moral certainty, relying heavily on circumstantial evidence that courts have consistently accepted when the facts form a coherent narrative of infidelity.