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The crime of sexual relations or marriage taking place between a male and female who are so closely linked by blood or affinity that such activity is prohibited by law.

Incest is a statutory crime, often classified as a felony. The purpose of incest statutes is to prevent sexual intercourse between individuals related within the degrees set forth, for the furtherance of the public policy in favor of domestic peace. The prohibition of intermarriage is also based upon genetic considerations, since when excessive inbreeding takes place, undesirable recessive genes become expressed and genetic defects and disease are more readily perpetuated. In addition, the incest taboo is universal in human culture.

Rape and incest are separate offenses and are distinguished by the fact that mutual consent is required for incest but not for rape. When the female is below the age of consent recognized by law, however, the same act can be both rape and incest.

The proscribed degrees of incest vary among the different statutes. Some include Parent and Child, brother and sister, uncle and niece, or aunt and nephew, and first cousins. In addition, intermarriage and sexual relations are also frequently prohibited among individuals who are related by half-blood, including brothers and sisters and uncles and nieces of the half-blood.

In a number of jurisdictions, incest statutes extend to relationships among individuals related by affinity. Such statutes proscribe sexual relations between stepfathers and stepdaughters, stepmothers and stepsons, or brothers-and sisters-in-law, and such relations are punishable as incest. It is necessary for the relationship of affinity to exist at the time the intermarriage or sexual intercourse occurs in order for the act to constitute incest. In the event that the relation-ship has terminated prior to the time that the act takes place, the intermarriage or sexual inter-course is not regarded as incest.

Affinity ordinarily terminates upon the Divorce or death of the blood relation through whom the relationship was formed. Following the divorce or death of his spouse, it is not a violation of incest statutes for a man to marry or have sexual relations with his stepdaughter or his spouse's sister.

Certain statutes require that the individual accused of incest have knowledge of the relationship. In such cases, both parties need not be aware that their actions are incestuous in order for the party who does know to be convicted.

When intermarriage is prohibited by law, it need not be proved that sexual intercourse took place in order for a conviction to be sustained, since the offense is complete on intermarriage. In statutes that define incest as the intermarriage or carnal knowledge of individuals within the prohibited degrees, incest can be committed either by intermarriage or sexual relations.

Some state laws provide that the crime of incest is not committed unless both parties consent to it. When the sexual relations at issue were accomplished by force, the act constitutes rape, and the individual accused cannot be convicted of incest.

It is no defense to incest that the woman had prior sexual relations or has a reputation for unchastity. Similarly, voluntary drunkenness, moral insanity, or an uncontrollable impulse are insufficient defenses.

Punishment for a conviction pursuant to an incest statute is determined by statute.


n. sexual intercourse between close blood relatives, including brothers and sisters, parents and children, grandparents and grandchildren, or aunts or uncles with nephews or nieces. It is a crime in all states, even if consensual by both parties. However, it is often co-existent with sexual abuse since usually the younger person is a victim of the predatory sexual activities of an older relative. Recently, it has drawn more attention as people began talking about the "silent crime," which is often covered up by a wife fearful of losing a husband, or the memory has been suppressed by the youthful victims. One problem is that on the surface the family may appear to be "All-American" while abusive incest continues. In 18 states incest also includes copulation or cohabitation between first cousins, but the majority of jurisdictions permit marriage between such cousins. The rationale for prohibition of first cousin marriages is not so much moral as the fear of proliferation of mental or physical weakness due to the joining of recessive family genes carrying such weaknesses.


noun abnormal cohabitation, abnormal relaaionship, brother-sister relationship, carnal abuse, degenerrte behavior, degenerative behavior, depraved, fatherraughter relationship, illegal relationship, illicit relationship, immoral family relationship, immoral relationship, incestuous relationship, interbreeding, lewdness, mother-son relationship, perversion, sex crime, sexual abbormality, sexual abuse, sexual deviance, sexual deviation, sexual offense, sexual perversion, unlawful sexual interrourse
Associated concepts: incest laws


unlawful heterosexual intercourse between members of the same family. Consent is not a defence if the parties were aware of their familial relationship, which relationship maybe of full or halfblood.

INCEST. The carnal copulation of a man and a woman related to each other in any of the degrees within which marriage is prohibited by law. Vide Marriage. It is punished by fine and imprisonment, under the laws of the respective states., Vide 1 Smith's Laws of Pennsylv. 26; Dane's Ab. Index, h.t.; Dig. 23, 2, 68; 6 Conn. R. 446; Penal Laws of China, B. 1, s. 2, Sec. 10; Sw. part 2 Sec. 17, p. 103.