I. How committed/Concept: The crime committed by a married man who:

1. Shall keep a mistress in the conjugal dwelling

a). the concubine must live in the conjugal dwelling even for brief periods of time, and not where she occasionally comes for a tryst or to spend the night therein

2. Shall have sexual intercourse with her under scandalous circumstances

a). Proof of sex is not necessary but may be inferred
b). There be a public or open flaunting of the illicit relationship so that the public is scandalized, shocked, or the conduct give rise to general protest, or that the relationship sets a bad example.
c). Example: being seen with the woman in social and public gatherings; introducing or treating the woman as though she were the wife   
d) Since public reaction is gauge of the scandal is there concubinage if:

   (i) openly going out is in places where the two are total strangers
   (ii) relatives and acquaintances accept the fact of the relationship, as when the wife left the man who now is cared and loved by another woman?

3. Cohabit with her in any other place

a). To cohabit is to live together as husband and wife.
b) QUESTION: Is concubinage committed by the man in providing the woman her own house or apartment but does not live with her though he regularly visits her thereat, at which time they engage in sex?    

II. Unlike in adultery, the fact of criminal conversation or sexual intercourse with a woman does not per se give rise to concubinage. Further, each sexual act is not a separate offense because concubinage is treated as a continuing crime.

Note:  In adultery the penalty is the same for both the woman and man (Prision correctional medium and maximum) but in concubinage the penalty for the man is lower by one degree ( prision correctional minimum and medium) while the  concubine is given a separate penalty which is destierro.

III. The woman is liable if she knows him to be married (even if unhappily at that and even if her purpose is to provide comfort and companionship)

IV. The defenses available in adultery also apply such as consent and pardon.