DOLO. - The term *dolo* is used in law in two distinct senses: as a defect of will in juridical acts, or as a subjective element of illicit acts, particularly crimes (v.).
I. In the first sense, *dolo* (more properly termed *dolus malus*, in contrast to *dolus bonus*) consists of deceits, maneuvers, or artifices employed to deceive someone into performing a juridical act that, had they not been deceived, they would not have performed (*dolus causam dantis*), or would have performed only under more advantageous conditions (*dolus incidens*).
It constitutes, together with error and violence, one of the three fundamental defects of will that may render a juridical act void or voidable. In reality, it may also be regarded as a subspecies of error, distinguished by the circumstance that the error is induced by another's deceit; indeed, the principles and norms relating to *dolo* come into consideration especially in cases where the error arising therefrom does not, in itself, invalidate the juridical act (i.e., independently of its being the result of another's deceit).
An act performed under another's deceit is generally not void but merely voidable (v. NULLITÀ*): that is, the deceived party or their heirs (and, for certain acts, any interested party) may, within a specified period (in Italian law, five years; canon law defers to civil law) from the discovery of the deceit, petition the judicial authority to have the act annulled. This applies, however, only if the deceit is of the *dolus causam dantis* type, i.e., such that, absent the deceit, the act would not have been performed; if, instead, it is *dolus incidens*, the act remains valid, though the author of the deceit is bound to compensate for damages (CIC, cann. 103 § 2 and 1684-85; Italian Civil Code arts. 624, 1439-46). In cases where the author of an act could seek its annulment for deceit (i.e., possesses what is termed an *azione di dolo*), they may also raise the defense of deceit (i.e., possess an *eccezione di dolo*) if sued to fulfill obligations arising therefrom (as explicitly stated in can. 1686).
It should further be noted that civil law generally accords no relevance to deceit in bilateral juridical acts (v. ATTO GIURIDICO) unless it is employed by one of the two contracting parties to the other's detriment, or, if employed by a third party, was known to the contracting party who benefits therefrom (cf. Italian Civil Code art. 1439).
The principles outlined above are sometimes derogated by law with respect to certain types of juridical acts. Such derogation may occur in two ways: either by deeming acts vitiated by deceit void (and not merely voidable)—though this is almost never the case—or by deeming them entirely valid (i.e., neither void nor voidable). A most important example of the latter derogation is found in canon law and in nearly all civil legislations with regard to marriage: in this context, deceit, even if employed by one party to the detriment of the other, does not affect the validity of the act; only error arising from deceit may render the marriage void (or, under civil law, voidable), provided such error would, independently of the deceit, have produced such invalidity in itself (v. ERRORE).
2. In matters of illicit acts, *dolo* is spoken of in contrast to fault (v.) when the author of an illicit act has acted with the intention of producing the harm or danger that constitutes the illicit act.
Outside the field of criminal law, illicit acts are considered primarily with regard to the obligation, arising therefrom, to compensate for damages. And since such an obligation exists whether the illicit act is committed with *dolo* or merely with fault in the strict sense, the distinction between *dolo* and fault is not of great importance: it may be said to have relevance only insofar as, when two parties stipulate an agreement exempting one from liability for damages caused to the other, such an agreement, if made prior to the commission of the illicit act, is void insofar as it concerns damages caused by *dolo*—i.e., the so-called *pactum de dolo non praestando* is void (and in modern law, based on Roman law, *dolo* is equated with gross fault).
The distinction between *dolo* and fault is, however, of the utmost importance in criminal law, since many offenses constitute crimes only if committed with *dolo* (v. DELITTO). For the moral aspect, V. FRODE.