1) The governing law and what “adultery” means (Philippine context)

In the Philippines, adultery is a criminal offense under the Revised Penal Code (RPC), Article 333. It is a gender-specific offense: it is committed by a married woman who has sexual intercourse with a man not her husband, and by the man who has sexual intercourse with her knowing she is married.

Adultery is different from concubinage (RPC, Art. 334), which penalizes certain forms of marital infidelity committed by a husband under different elements and penalties.

2) Elements of adultery (RPC, Article 333)

To convict, the prosecution must prove the elements beyond reasonable doubt.

2.1. For the married woman

She is legally married (a valid subsisting marriage at the time of the act), and
She had sexual intercourse with a man not her husband.

Key point: For the woman, there is no separate “knowledge” element (she is presumed to know she is married).

2.2. For the man (the paramour)

He had sexual intercourse with the married woman, and
He knew she was married.

Knowledge matters for the man. If he genuinely did not know she was married (and the circumstances reasonably support that), that can defeat liability for him—even if the woman may still be liable if the other elements are proven.

2.3. “Sexual intercourse” is indispensable

Adultery requires carnal knowledge/sexual intercourse. Evidence showing only:

dating,
affectionate behavior,
staying together,
“sweetheart” messages,
cohabitation,
hotel check-ins,
being found alone in a room,

may be relevant, but the prosecution still must prove intercourse, usually through strong circumstantial evidence or admissions. Mere suspicion or moral certainty is not enough in criminal law.

2.4. Each act can be a separate count

As a rule in practice, each act of sexual intercourse can be charged as a separate offense, so multiple incidents can mean multiple counts—if each act is adequately supported by evidence.

3) The penalty for adultery (RPC, Article 333)

3.1. Principal penalty

Both offenders—the married woman and the paramour—are punished by:

Prisión correccional in its medium and maximum periods

This corresponds to an imprisonment range of:

2 years, 4 months, and 1 day up to 6 years

(The medium period of prisión correccional starts at 2 years, 4 months, and 1 day; the maximum period ends at 6 years.)

3.2. Accessory penalties (important in practice)

Because the penalty is prisión correccional, it generally carries accessory consequences under the RPC, such as suspension from certain public rights/privileges during the term of sentence (commonly affecting public office, profession/calling, and suffrage rights while serving the sentence, depending on the final judgment and the offender’s circumstances).

3.3. Bail, probation, and sentencing realities

Bail: Adultery is generally bailable (it is not a capital offense).
Indeterminate Sentence Law (ISL): Courts typically impose an indeterminate sentence (minimum and maximum term) if convicted, subject to ISL rules.
Probation: Depending on the final imposed sentence and the offender’s eligibility under the Probation Law, probation may be legally possible in some cases (this is fact- and sentence-dependent).

4) Adultery is a “private crime”: who can file and how (RPC, Article 344)

4.1. Only the offended spouse can initiate prosecution

Adultery cannot be prosecuted unless a complaint is filed by the offended spouse. For adultery, the offended spouse is typically the husband of the woman.

This is not the same as a police blotter entry. A complaint for criminal prosecution is usually filed through the prosecutor’s office (or proper court process where applicable), supported by affidavits and evidence.

4.2. The complaint must include both guilty parties (if both are alive)

A central rule for adultery and concubinage:

The offended spouse cannot institute criminal prosecution without including both guilty parties, if both are alive.

So, a complaint that targets only the wife or only the paramour (when both are alive) is generally defective.

4.3. Consent or pardon bars prosecution

Also under the private-crime framework:

If the offended spouse consented to the adultery (prior consent), or
pardoned/condoned the offenders (often an issue when the spouse forgives and resumes marital relations with knowledge of the affair),

the offended spouse generally loses the right to prosecute.

Timing matters most before filing. In many real cases, what becomes litigated is whether the offended spouse’s conduct amounts to implied pardon/condonation, such as continuing cohabitation after discovering the affair.

4.4. Death of the offended spouse

If the offended spouse dies before filing the complaint, adultery generally cannot be initiated by others (it is personal to the offended spouse).
If the complaint was already properly filed and the case commenced, the case is typically treated as a public prosecution thereafter, even if the offended spouse later becomes unavailable—though practical proof issues can arise.

5) Proof and evidence: what usually wins or loses an adultery case

5.1. The hard part: proving sexual intercourse beyond reasonable doubt

Because adultery requires intercourse, evidence must be stronger than “they were probably intimate.” Common evidentiary sources include:

Admissions/confessions (careful: voluntariness and admissibility matter)
Eyewitness testimony (rare)
Highly persuasive circumstantial evidence that logically and convincingly establishes intercourse, not merely opportunity

5.2. Digital evidence (texts, chat logs, photos, videos)

Digital evidence can be powerful, but two practical issues often arise:

Authentication (proving the messages/accounts belong to the accused and weren’t altered), and
Legality of acquisition (illegally obtained recordings or intercepted communications can expose a party to liability and may be inadmissible depending on how they were obtained and presented).

5.3. Venue and particularity

Because each intercourse incident can be a separate count, the complaint often needs to be particular enough as to time and place to establish venue and to inform the accused of the charge.

6) Common defenses in adultery cases

6.1. No valid marriage at the time of the act

A core element is that the woman is married. Issues may arise when:

The marriage is alleged to be void from the start, or
There is a dispute about the validity/existence of the marriage.

(For voidable marriages, the general legal concept is that the marriage is treated as valid until annulled; this can matter in timing-based defenses.)

6.2. No sexual intercourse proven

If the evidence shows only intimacy, cohabitation, or opportunity—but not intercourse beyond reasonable doubt—acquittal is possible.

6.3. Lack of knowledge for the man

The paramour must have knowledge that the woman was married. If he can credibly show he did not know and had no reasonable basis to know, this can defeat his criminal liability.

6.4. Consent, pardon, or condonation by the offended spouse

Demonstrating that the offended spouse consented or pardoned/condoned can bar prosecution (often litigated through the spouse’s actions after discovery).

6.5. Prescription (time-bar)

Crimes punishable by correctional penalties generally prescribe in 10 years under the RPC rules on prescription, and adultery falls under that penalty class. Delay can thus become a decisive defense depending on dates and how the offense is charged.

6.6. Procedural defects unique to private crimes

Examples:

Complaint not filed by the offended spouse,
Failure to include both offenders when both are alive,
Complaint filed by someone without legal standing.

7) How adultery differs from concubinage (why this matters)

Adultery (Art. 333) punishes the wife and the man for sexual intercourse.

Concubinage (Art. 334) punishes the husband under more specific circumstances (e.g., keeping a mistress in the conjugal dwelling, cohabiting under scandalous circumstances, or having sexual intercourse under scandalous circumstances), with different penalties and treatment of the woman involved (often destierro for the concubine in certain convictions).

Practical impact: Adultery is generally easier to define (intercourse + marriage) but hard to prove; concubinage has narrower legal triggers but can sometimes be proven through cohabitation facts that fit the statute.

8) Relationship to family law remedies (parallel consequences)

Criminal adultery is separate from civil/family proceedings, but the same conduct can have parallel effects:

Legal separation: Sexual infidelity is a recognized ground for legal separation under the Family Code (distinct from annulment/nullity).
Custody/parental authority: Courts decide based on the child’s best interests; infidelity may be weighed as a factor depending on circumstances, but it is not automatically determinative.
Civil damages: In some situations, marital infidelity is invoked in civil actions for damages under general civil law principles, but outcomes are highly fact-specific and depend on pleadings and proof.

9) Practical notes on charging, negotiations, and case dynamics

Because adultery is a private crime, the offended spouse’s choice to file (or not file), and issues like condonation, heavily shape the case.
Many cases turn on whether the evidence proves intercourse rather than mere closeness or cohabitation.
Where multiple incidents are alleged, the prosecution’s burden generally rises: evidence must meaningfully support each charged act.

10) Summary: the “must-know” points

Adultery (RPC Art. 333) is committed by a married woman who has sexual intercourse with a man not her husband, and by the man who does so knowing she is married.
Penalty: prisión correccional (medium to maximum) = 2 years, 4 months, 1 day to 6 years, plus accessory consequences associated with that penalty.
It is a private crime: prosecution generally requires a complaint by the offended spouse, must include both offenders if alive, and is barred by consent/pardon/condonation.
The battleground is usually proof of sexual intercourse and procedural validity of the complaint.