1) The Philippine crime of adultery in one sentence

In the Philippines, adultery is a crime committed when a married woman has sexual intercourse with a man not her husband, and the man knows she is married.

This is distinct from (and treated differently than) concubinage, which penalizes certain forms of extramarital conduct by a married man.

2) Legal basis and why “knowledge” matters

Revised Penal Code (RPC), Article 333 (Adultery)

Article 333 of the Revised Penal Code defines and penalizes adultery. While the statutory text is brief, Philippine jurisprudence and standard criminal law treatment recognize specific elements that the prosecution must prove beyond reasonable doubt.

A key feature of adultery (unlike many ordinary crimes) is that criminal liability for the male participant depends on his knowledge of the woman’s married status.

3) Elements of adultery (what must be proven)

To convict both accused, the prosecution generally must establish:

The woman is married (a subsisting marriage at the time of the act).
She had sexual intercourse with a man not her husband.
The man knew the woman was married.
The sexual intercourse was voluntary (i.e., not rape or otherwise non-consensual as to either accused).

The short answer to the headline question

Yes: as a rule, the paramour must know the woman is married to be convicted of adultery.

4) What “knowledge” of marriage means

A) Knowledge is an essential element for the male accused

The law does not treat the male participant as strictly liable. The prosecution must show that he knew (or, in practice, that it is proven beyond reasonable doubt he was aware) that the woman was married.

Why? Because adultery is considered a crime where the man’s participation is culpable only if he consciously joins in violating the marital relation.

B) How knowledge is proven (direct or circumstantial)

Knowledge is rarely proven by an outright admission. It is commonly inferred from circumstances, such as:

The woman introduced herself as married or spoke about her husband.
The man knew her as using a married surname, living with a husband, or having children recognized as part of a marital household.
The relationship occurred in contexts where marriage would be obvious (e.g., frequent presence at the family residence, social circles where her status was openly known, meeting the husband, etc.).
Messages/letters showing the man acknowledged the woman’s marital status.
Community or workplace setting where her being married was not hidden and the man had close association.

What matters is not gossip, but whether the totality of evidence convinces the court beyond reasonable doubt that he knew.

C) “Should have known” vs. “actually knew”

Philippine criminal law is generally cautious about convicting on mere negligence unless the offense is defined that way. For adultery, courts look for proof that supports the conclusion the man actually knew (even if inferred from circumstances). Suspicion or careless failure to verify, by itself, is usually not treated as enough for conviction if reasonable doubt remains.

5) What if the man truly didn’t know she was married?

A) Good-faith mistake of fact can acquit the man

If the man credibly shows he honestly and reasonably believed the woman was single (or otherwise not married) and the prosecution cannot disprove knowledge beyond reasonable doubt, the man may be acquitted.

B) But the married woman can still be convicted

The married woman’s liability does not depend on the man’s knowledge. If she is married and voluntarily had intercourse with a non-husband, the elements as to her are complete (subject to defenses like lack of marriage, lack of intercourse, lack of voluntariness, or procedural bars like pardon/condonation).

So, it is legally possible for outcomes like:

Woman convicted, man acquitted (due to failure to prove his knowledge).

6) The “married woman” element: what counts as married?

A) Marriage must be shown to exist at the time of intercourse

Typically proven through:

Marriage certificate / civil registry records
Testimony on the marriage and identity of parties

B) What about annulment/nullity later?

This is a nuanced area because criminal courts avoid allowing accused persons to collaterally attack marital status in ways that belong in family courts.

Practical points:

If a marriage is later declared void, parties often argue that there was “no marriage” to begin with.
However, Philippine practice and jurisprudential themes in related crimes (notably bigamy) emphasize that marital status is presumed and that a judicial declaration is the orderly way to establish nullity for legal purposes.

Because results can depend heavily on the timing of the declaration, the exact ground of nullity, and how the issue is raised, this is an area where case-specific legal advice is essential. Courts tend to focus on whether, at the time of the alleged act, the woman was treated in law and in fact as a spouse under a subsisting marriage.

C) Legal separation or de facto separation

Legal separation does not dissolve the marriage. The parties remain married; adultery can still be committed.
Being separated in fact, living apart, or having an “understanding” does not erase criminal liability.

7) The “sexual intercourse” element: not just intimacy

Adultery requires carnal knowledge (sexual intercourse). This is stricter than “romantic involvement” or “cohabitation.”

A) Proof issues

Direct eyewitness proof is rare. Courts often rely on:

Admissions (messages, letters, testimony)
Strong circumstantial evidence that points to intercourse, not merely companionship

But courts also guard against convicting based purely on:

Mere presence together in a room
Rumors, reputation, or suspicion
“Sweetheart” behavior without proof of intercourse

Because the standard is beyond reasonable doubt, weak circumstantial evidence often fails.

B) Attempted adultery?

Adultery is typically treated as consummated by intercourse. Conduct short of intercourse may have consequences (civil, administrative, or other criminal laws depending on the act), but it does not automatically satisfy Article 333.

8) Voluntariness: what if the act wasn’t consensual?

If the intercourse occurred through force, intimidation, or circumstances constituting rape:

The married woman is not guilty of adultery if she did not voluntarily participate.
The male may face liability for rape (a different offense) rather than adultery.

9) Procedural rules unique to adultery: who can file, and what can stop the case

Adultery is not prosecuted like an ordinary public crime in the sense of “anyone can complain.”

A) Only the offended spouse can initiate prosecution

A criminal action for adultery generally requires a complaint filed by the offended husband (the spouse offended by the act). Without this, the case cannot proceed.

B) The complaint must include both offenders (as a rule)

The offended spouse cannot typically “pick only one” (e.g., sue only the paramour but not the wife) if both are alive and identifiable. The design is to prevent harassment or selective prosecution that weaponizes the criminal process.

C) Consent, pardon, and condonation

Adultery cases can be barred or defeated by:

Consent (prior permission or approval)
Pardon (express or implied), often inferred from conduct like reconciliation in some circumstances

The details are intensely factual: what was said/done, when, and whether the offended spouse truly forgave or accepted the act in a legally meaningful way.

D) Prescription (time limits)

Adultery has a correctional penalty; as a rule, crimes punishable by correctional penalties prescribe in 10 years. The computation and interruption of prescription can be technical (e.g., filing of complaint, preliminary investigation), so actual deadlines are case-specific.

10) Penalties and collateral consequences

A) Criminal penalty

Adultery is punished by prisión correccional in its medium and maximum periods (within the correctional range).

B) Civil and family-law consequences (separate from criminal case)

Even if a criminal case is not filed or does not prosper, adultery-related conduct can still matter in:

Legal separation (marital infidelity is a ground)
Damages in certain contexts (depending on pleadings and proof)
Disinheritance and other civil law effects (under the Civil Code’s rules on causes, where applicable)
Child custody and parental authority issues (always governed by the child’s best interests, not automatic punishment)

C) Administrative/workplace consequences

For public officials, lawyers, or licensed professionals, extramarital conduct can trigger administrative discipline (a separate process with different standards).

11) Comparison with concubinage (why the law asks the question differently)

A frequent confusion is treating adultery and concubinage as mirror images. They aren’t.

Adultery (Art. 333): focuses on the married woman’s intercourse and penalizes the male paramour if he knew she was married.
Concubinage (Art. 334): penalizes a married man only under specific aggravated circumstances (e.g., keeping a mistress in the conjugal dwelling, cohabiting under scandalous circumstances, etc.). It is generally harder to prove and structured differently.

This asymmetry is often criticized as gendered, but it remains in the Revised Penal Code unless amended by law or reinterpreted by controlling doctrine.

12) Practical takeaways on the “paramour’s knowledge” requirement

Yes—knowledge is required to convict the male paramour of adultery.
The prosecution must prove that knowledge beyond reasonable doubt, often through circumstantial evidence.
A credible good-faith belief that the woman was not married can create reasonable doubt for the man.
The woman may still be convicted even if the man is acquitted, because her liability does not hinge on his knowledge.
Adultery cases are highly procedural: no complaint by the offended spouse, no case, and pardon/condonation can be fatal to prosecution.

13) If you’re dealing with a real situation

Because adultery cases turn on (1) proof of intercourse, (2) proof of the man’s knowledge, and (3) procedural bars like pardon/condonation and proper filing, a short consultation with a Philippine criminal lawyer can radically change what is realistic to file, defend, or settle.

If you want, paste a hypothetical fact pattern (no names) and I can map it to the elements and the common evidentiary pitfalls.