The term incest refers to any sexual activity that takes place between non-spouse family members or close relatives. Incest is illegal in the United States and many other countries around the world. Incest laws are intended to protect the security of the family, and to prevent the genetic defects that typically occur when babies are born of parents too closely related. To explore this concept, consider the following incest definition.

Definition of Incest


  1. Sexual activity between people who are very closely related.
  2. The crime of marriage, cohabitation, or sexual intercourse between people that are too closely related, as defined by law.


1175-1225        Middle English  < Latin incestus

What is Incest

U.S. law recognizes that sexual relations between closely related individuals poses a serious risk of serious genetic birth defects in any resulting offspring. These problems include such conditions as stillbirth, SIDS, mental retardation, developmental disabilities, heart conditions, and other physical abnormalities. In addition to the risk to babies born of such relationships, incest poses a serious threat to the family relationship.

Incest between an adult and closely related child is considered child sexual abuse, and even sexual relations between adult members of a family who are too closely blood-related tends to disrupt the normal power and authority dynamics within a family. For these reasons, incest, in all of its definitions, is illegal in every state in the United States.

Incest Laws

Incest is regulated by the laws of each state, not federal law, and these laws vary greatly. Each state defines what is considered “family,” for the purposes of incest, and the exact relations or circumstances that are deemed illegal. For instance, in New Jersey, there is no criminal penalty for incest if both parties are of legal age, though marriage between related adults is illegal. Most states outlaw sexual relations between blood relatives, but some also include step-family, foster family, and adoptive relatives. This is because of the abuse factor, and the disruption of normal familial relationships.

All states define close family as parents and children, aunts and uncles, grandparents, and first cousins for the purposes of incest. Some states allow relationships between more distant cousins, if the participants are both of legal age and consenting. In most cases, the more distant the blood relation, the less likely the relationship is to be considered incest.

Incest Sex

Some states, marrying, cohabiting, or other intimate relationship between individuals too closely related to be incest, even without sexual relations. In every state, however, incest sex, which is any sexual activity between closely related blood relatives, and any other family members defined by law, is illegal. In an effort to protect children and other individuals from incestuous activity, there are generally no specific acts defined as incest sex, but the term is broadly defined as any sexual act or activity.

For example:

Sixteen-year old Paul, and 15-year old Celeste, have always been close as siblings, and have been experimenting with oral sex for about a year. Regardless of what their state’s age of consent for sex is, sexual relations of any nature between siblings is against the law. A prosecutor may choose to file incest charges against both teens. The two risk a jail term, and will likely be separated, and possibly ordered by the court to attend counseling.

Prosecution of Incest

In cases involving incest, prosecutors in most states have discretion in which specific charges to bring against a defendant. This is because incest is often a complex situation, and multiple criminal laws may be involved. For instance, an individual accused of incest may be charged with molestation, rape, or lewd acts, in addition to, or instead of, incest.

In cases in which an adult and child are involved, or an adult who began an incestuous relationship when the other individual was a child, the adult would be charged, and not the child, who is considered a victim. If, on the other hand, two siblings of a similar age engaged in incest, both might be charged. While age might determine who is charged with a crime, it is never a defense to incest, or any related criminal charges. Neither is consent a defense to incest, as the act itself is against the law, and both parties may be charged. If one party did not consent, but was forced or coerced, the defendant may also be charged with rape, molestation, or other crimes.

For example:

Mary has been involved in a sexual relationship with her father, Henry, since she was 13 years old. Now, at the age of 21, another family member has reported to the authorities that the father and daughter live together as a married couple. Although Mary is now an adult, and tries to convince the prosecutor that her relationship with her father is consensual, it is still illegal. Mary is not likely to face any criminal charges, as she was a minor when her father began the relationship. Henry, however, may be charged with incest, statutory rape, child sexual abuse, or any of a number of related offenses.

Penalties for Incest

Incest, whether between adults, or involving a child, is a felony in all states. Penalties for incest vary by state, as well as the specific nature of the criminal charges. In a case involving incest between adults, the perpetrators may face imprisonment ranging from several months to several years.

Incest involving a child, or one adult who was a minor when the relationship began, involves much more severe punishment. In such a case, the family may be separated, to remove the child from the home, the adult will likely be charged with some form of child sexual abuse, and face a prison term of many years. In addition, he or she will be required to register as a sex offender for life.

Real Life Incest Cases

Non-Custodial Mother and Son

In 2012, a 32-year old California woman was charged with incest with her teenage son, after an investigation into her sending of sexually explicit electronic messages to the boy. The woman, who had abandoned the boy to his father at the age of two, allegedly sent video messages to the teen’s phone showing the two engaging in oral sex and sexual intercourse. The woman pled no contest, which had the effect of a guilty plea for sentencing purposes, in exchange for a promise of no additional charges, and a lighter sentence of 4 years, 8 months in the state prison.

University Professor and Adult Daughter

In 2012, David Epstein, a 46-year old science professor at Columbia University in New York, faced incest charges because of his sexual relationship with his adult daughter. This case enraged the public, when Epstein’s attorney argued in a press interview, “there is an argument to be made in the Swiss case to let go what goes on privately in bedrooms … It’s OK for homosexuals to do whatever they want in their own home. How is this so different?”

In a plea bargain reached after Epstein’s daughter refused to testify, Epstein pled guilty to a misdemeanor of attempted incest, and kept his position as a professor at the university.

Daughter Bears Four Children to Father

Daniel Rinehart began raping his daughter, Ashley, when she was five years old. Ashley’s mother, Linda, knew about the abuse but did not interfere, and the younger siblings were threatened with death in order to keep the family secret. In 2009, one of Ashley’s sisters escaped from the home and called the police. She told the police that Ashley had given birth to four babies by her father, only one of which survived birth. The three dead infants were disposed of in a cooler, left on a farm. The fourth baby had survived, and was four years old at the time of the report.

The court ignored Rinehart’s claim that his relationship with his daughter was consensual, claiming she showed interest in a sexual relationship with him by rubbing his shoulders. Rinehart was tried by a jury for charges of incest, statutory rape, murder, and abandoning a corpse, in 2010, and sentenced to life in prison, plus 22 years.

Related Legal Terms and Issues

  • Consent – To agree, approve, permit, comply, or yield.
  • Criminal Act – An act committed by an individual that is in violation of the law, or that poses a threat to the public.
  • Defendant – A party against whom a lawsuit has been filed in civil court, or who has been accused of, or charged with, a crime or offense.
  • Felony – A crime, often involving violence, regarded as more serious than a misdemeanor. Felony crimes are usually punishable by imprisonment more than one year.
  • Jurisdiction – The legal authority to hear legal cases and make judgments; the geographical region of authority to enforce justice.
  • Misdemeanor – A criminal offense less serious than a felony; generally those punishable by a fine, probation, community service, or imprisonment of less than one year.
  • Perpetrator – A person who commits an illegal or criminal act.
  • Victim – A person who is injured, killed, or otherwise harmed as a result of a criminal act, accident, or other event.