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A Genetic Report Should Cause A Rethinking Of Incest Laws

Monday, Apr. 08, 2002

Jerry Lee Lewis is notorious for having married his cousin. So are Charles Darwin and Albert Einstein. All three suffered for having violated a widely held social norm against "incestuous" unions. Yet there may be less reason for this norm, and for the laws enforcing it, than was once believed.

A panoply of state laws say cousin marriages are taboo. But a new report in the Journal of Genetic Counseling, described in the New York Times last week, might send state lawmakers back to work revising their incest laws.

The report concludes that cousins can have children together without running much greater risk than a "normal" couple of their children having genetic abnormalities. Accordingly, the report potentially undermines the primary justification for laws that prevent first cousins from marrying or engaging in sexual relations with one another.

The Laws Regulating Incest in Different States

Criminal laws prohibit marriage and sexual relationships based on the same ties (with the necessary consanguinity and affinity usually defined the same way as in the marriage laws). They penalize those who disobey with fines or imprisonment.

Every state today has a statute defining eligibility for marriage, and each and every one prohibits marriages between parents and children, sisters and brothers, uncles and nieces, and aunts and nephews. Some prohibit all ancestor/descendant marriages, regardless of degree. Four states extend the prohibition to marriages between parents and their adopted children.

Twenty-four states prohibit marriages between first cousins, and another seven permit them only under special circumstances. Utah, for example, permits first cousins to marry only provided both spouses are over age 65, or at least 55 with evidence of sterility. North Carolina permits first cousins to marry unless they are "double first cousins" (cousins through more than one line). Maine permits first cousins to marry only upon presentation of a certificate of genetic counseling. The remaining nineteen states and the District of Columbia permit first-cousin marriages without restriction.

The Origins of Incest Laws

Incest laws in this country have largely religious origins. In England, incest was punishable only in ecclesiastical courts, which ostensibly applied the law of Leviticus prohibiting persons more closely related than fourth cousins to marry. This ban applied equally to relations by blood and by marriage, based on the canonical maxim that husband and wife were one, and therefore equally related to each other's kin.

American jurisdictions departed from English law by declaring incest a crime, as well as a basis for invalidating marriage. However, many states only punished relationships between first cousins and closer, and others only punished relationships of consanguinity, but not affinity.

The Modern Justifications for Incest Laws

Today, the justifications given for retaining statutory prohibitions on cousin marriage (and even debating the passage of new ones) are largely based on the fear that such unions will cause genetic problems for the children they produce.

The states that permit cousin marriage only under certain circumstances make this underlying justification clear - since a common thread runs through all their laws. Each requires a showing that the couple will not reproduce (because of age or sterility) or, at the very least, that they have undergone counseling to understand the risks of reproduction.

According to Mead, the taboo has strong benefits: Because certain sexual and marital relationships are categorically forbidden, and the categorical ban is instilled early on in children's minds, children can grow and develop affectionate, close bonds with a wide span of relatives, without the intrusion of "inappropriate sexuality." Children can "wander freely, sitting on laps, pulling beards, and nestling their heads against comforting breasts--neither tempting nor being tempted beyond their years."

Levi-Strauss focused on the benefits of the incest taboo to society at large. The ban on intrafamily marriage forces families to reach outward and connect with other families--and it is those connections between many different families that make society function.

Possible Constitutional Challenges to Incest Laws

Will the new data - which strongly suggest, for cousins, that the genetic justification does not hold water - mean that state prohibitions on cousin-marriages are vulnerable to constitutional attack? Certainly, the new data dramatically strengthen the basis for such an attack.

The Supreme Court, in a long line of due process cases establishing the right to make important decisions about family life, has treated the right to marry as fundamental. State laws that significantly interfere with the right to marry have, therefore, been subjected to heightened scrutiny. In other words, states must show that they have a compelling reason for restricting the right to marriage, and that they have chosen means that are closely related to their stated goals.

What will the states assert as the "compelling interests" that justify banning cousin marriage? One might be the desire to discourage reproduction when the children are likely to have significant birth defects. Another might be the desire to preserve intrafamily harmony. (The desire to replicate Levitical law would, of course, not be a legitimate interest for a state, given the Constitution's ban on state establishment of religion). These ends are probably sufficiently compelling under a constitutional analysis.

The problem comes in another component of the constitutional analysis - the "narrow tailoring" requirement, which tests the closeness of the relationship between the state's chosen means and its desired ends. According to the recent report, children of unrelated parents have a 3 to 4 percent chance of being born with a serious birth defect. Children of first cousins have only a slighter higher risk--roughly a 4 to 7 percent chance. Thus the ban on cousin marriages will not go very far toward the general problem of preventing birth defects.

Likewise, the concerns about intrafamily harmony are most compelling with respect to members of the same household, and thus seldom implicated in our culture, where it is fairly unusual for first cousins to grow up in close confines. The potential for family disruption is limited where cousins grow up in separate households and then marry as adults. A few courts have applied this reasoning to invalidate incest laws with respect to couples with no blood relation, like a step-sister and step-brother who became related only as adults when their parents married.

The prohibition of cousin marriages suffers from problems of both under- and over-inclusiveness--flaws that are usually fatal to a statute under heightened scrutiny. These bans are underinclusive in that they do not prohibit marriage in other cases where the risk of producing children with birth defects is significant. Carriers of diseases like cystic fibrosis, for example, are permitted to marry and reproduce with other carriers, even though resulting children have a 1 in 4 chance of developing the disease. For most individuals, the decision whether to marry and reproduce in the face of known risks to resulting children is left to their discretion.

More generally, scientific advances that enable doctors to screen for many potentially harmful genes may render general presumptions about genetic risks, like those embodied in marriage bans, inappropriate. When a particular individual can know his or her specific risk of passing on dangerous genes to children, how can a presumption as to the average person's general risk of doing so constitutionally be applied?

Will Cousins be Allowed to Marry?

Prohibitions on cousin marriage are unique to the United States. Most other countries permit first-cousin marriages without restriction, and the rate of cousin marriages in some countries is as high as 60 percent of all marriages. But that has always been the case, and being unique has rarely motivated Americans to change their ways.

A constitutional challenge to a state's ban on cousin marriage may well be successful, and studies like this recent one will be important to such a case. But even if legal barriers to cousin marriage are removed, the cultural taboo (the so-called "ick" factor) will be harder to remove.

The term "incest" - which conjures an image of a sexually exploitative relationship between an older male relative and a young girl - is one barrier to cultural change. Cousin marriages between two adults are not, of course, incestuous in this sense.

Just as the term "bastard" gave way first to "illegitimate child" and later to "nonmarital child" in the literature on unwed parenting, perhaps "incest" could be replaced with more palatable terms like "kinship marriage" or "distant consanguineous relationships."

Beyond nomenclature, cousin marriage faces other barriers. Regardless of widely reported scientific advances, many will continue to believe that cousin couples are destined to produce genetically inferior offspring. Just two years ago, one Maryland legislator spoke in favor of a proposed bill to prohibit cousin marriage, claiming that 1 in 32 children born to cousins has a birth defect, compared to 1 in 100,000 born to unrelated parents. Correcting such misperceptions will be important to the success of those advocating for cousin marriage.

Joanna Grossman, a FindLaw columnist, is an associate professor of law at Hofstra University. Grossman's articles on family law and other issues may be found in the archive of her pieces on

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