(dissenting).
It is the exclusive prerogative of this court to determine the constitutionality of Iowa statutes challenged under article I, section 6, the equal protection clause of the Iowa Constitution. Callender v. Skiles, 591 N.W.2d 182, 187 (Iowa 1999). Even if the Iowa Constitution and the United States Constitution are similarly or identically phrased, we can independently consider Iowa constitutional arguments. Racing Ass’n of Cent. Iowa v. Fitzgerald, 675 N.W.2d 1, 6 (Iowa 2004) (citing William J. Brennan, Jr., State Constitutions and the Protection of Individual Rights, 90 Harv. L.Rev. 489, 500 (1977)). “This result is particularly possible in view of ‘the ill-defined parameters of the equal protection clause.’ ” Id. (quoting Miller v. Boone County Hosp., 394 N.W.2d 776, 781 (Iowa 1986)).
Our case law gives us the analytical framework to decide whether a statute violates the equal protection clause of the Iowa Constitution. Racing Ass’n of Cent. Iowa, 675 N.W.2d at 7-9. In analyzing an equal protection challenge under the Iowa Constitution, we must first determine whether the legislature had a valid reason to treat a person cohabitating with a sex offender differently than other persons who have a relationship with a sex offender. Id. at 7. This determination requires us to find a plausible policy reason for the classification. Id. In making this determination, our court must not only ask whether the statute serves a legitimate government purpose, but also whether the claimed state interest is realistically conceivable. Id. Second, we must decide whether the State’s claimed reason has a basis in fact. Id. at 7-8. To decide whether the State’s claimed reason has a basis in fact, we must determine whether the legislature could rationally believe facts upon which the classification is based are true. Id. at 8. Lastly, we must consider whether the relationship between the classification, i.e., the differences between persons cohabitating with sex offenders and persons with other relationships to sex offenders, and the purpose of the classification is so weak that the classification must be viewed as arbitrary. Id. In other words, to uphold the statute, we must conclude “the relationship of the classification to its goal is not so attenuated as to render the distinction arbitrary or irrational.” Nordlinger v. Hahn, 505 U.S. 1, 11, 112 S.Ct. 2326, 2332, 120 L.Ed.2d 1, 13 (1992) (citations omitted).
I cannot agree with the majority’s conclusion that “unmarried cohabitation of a parent with a sex offender poses greater danger to children than cohabitation between married persons” because as the majority contends
a sex offender married to the parent will have a greater sense of commitment to the family unit created by the marriage *441and that the marital relationship may impose on the sex offender greater financial and other obligations toward the family, so that the sex offender feels he or she has a stake in the well-being of the children.
The Code does not define cohabitation. Our existing case law defines cohabitation as having two elements. In re Marriage of Gibson, 320 N.W.2d 822, 824 (Iowa 1982). First, an unrelated person must be living or residing in the dwelling. Id. Second, the two unrelated persons must be living together in the manner of husband and wife. Id. In other words, cohabitation is essentially a marriage without the license. The commitment to the family unit, the financial obligations, and other obligations of a cohabiter to maintain the family unit is no more or less than that of a married individual. It is absurd to think that the financial implications of a dissolution will provide a greater deterrent than the stiff criminal penalties the legislature has enacted for sex offenders. Moreover, our present laws allow the department of social services to remove a child from the home of a sex offender. Accordingly, I would hold the relationship of the classification, marriage versus cohabitation, to the goal of protecting children living in the home with a sex offender is so attenuated as to render the distinction arbitrary or irrational.
This attenuation is amplified when we employ an overinelusive-underinclusive dichotomy analysis under the Iowa Constitution to determine whether the relationship of the classification to its goal is not so attenuated as to render the distinction arbitrary or irrational. Compare Racing Ass’n of Cent. Iowa, 675 N.W.2d at 10 (finding the legislative purpose behind a taxation provision cannot withstand rational basis review because of the extreme degrees of overinclusion and underinclusion), and Bierkamp v. Rogers, 293 N.W.2d 577, 584 (Iowa 1980) (finding a classification based on extreme degrees of overinclusion and underinclusion cannot pass rational basis review), with Vance v. Bradley, 440 U.S. 93, 108, 99 S.Ct. 939, 948, 59 L.Ed.2d 171, 183 (1979) (demonstrating the United States Supreme Court’s tolerance for laws that are overin-clusive and underinclusive when conducting a rational basis review). When we find “a classification involves extreme degrees of overinclusion and underinclusion in relation to any particular goal,” then that statute fails rational basis review. Bierkamp, 293 N.W.2d at 584; see also Racing Ass’n of Cent. Iowa, 675 N.W.2d at 10.
Section 726.6(1)(⅛ )’s reach is limited. It provides:
1. A person who is the parent, guardian, or person having custody or control over a child or a minor under the age of eighteen with a mental or physical disability, or a person who is a member of the household in which a child or such a minor resides, commits child endangerment when the person does any of the following:
[[Image here]]
h. Cohabits with a person after knowing the person is required to register or is on the sex offender registry as a sex offender under chapter 692A. However, this paragraph does not apply to a person who is a parent, guardian, or a person having custody or control over a child or a minor who is required to register as a sex offender, or to a person who is married to and living with a person required to register as a sex offender.
Iowa Code § 726.6(1)(⅛) (Supp.2005). Cohabitation is fact specific and applies to a very narrow range of relationships. Compare In re Marriage of Gibson, 320 N.W.2d at 824 (finding that an unrelated *442male who spent four nights a week at his girlfriend’s house, maintained an ongoing sexual relationship with her, ate meals at her house, but did not share expenses or have unlimited access to the house was not cohabitating), with In re Marriage of Harvey, 466 N.W.2d 916, 917-18 (Iowa 1991) (finding that an unrelated male who spent five nights a week at his girlfriend’s house, maintained an ongoing sexual relationship with her, ate meals at her house, shared expenses, and had unlimited access to the house was cohabitating).
The relationships not covered by this statute include persons married to a sex offender, persons living with a sex offender, but not cohabitating, persons having a serious dating relationship with a sex offender, persons having a casual dating relationship with a sex offender, persons who are friends with a sex offender, persons who are acquaintances of a sex offender, persons who are related to a sex offender, and persons who hire a sex offender to do work for them. In each of these situations, the sex offender may have access to a child in the home. Moreover, access by some of these individuals may be unlimited.
The relationship that section 726.6(1)(⅞) criminalizes makes the statute both overin-clusive and underinclusive. Further, the degree to which this overinclusiveness and underinclusiveness is present is extreme because it is irrational to suppose a sex offender cohabitating in a person’s home will have greater access to a child in that home than a sex offender who is married to the person, a sex offender who is living with the person, but not cohabitating, a sex offender who is having a serious dating relationship with the person, a sex offender who is having a casual dating relationship with the person, a sex offender who is a friend to the person, a sex offender who is acquainted with the person, a sex offender who is related to the person, and a sex offender who is hired by the person to do work for them. The extreme overinclu-siveness and underinclusiveness of the statute makes the relationship between the classification and the legislative purpose of keeping sex offenders from having access to children arbitrary; therefore, the statute does not withstand review under the rational basis test we have developed under the Iowa Constitution. See Racing Ass’n of Cent. Iowa, 675 N.W.2d at 10 (finding the legislative purpose behind a taxation provision cannot withstand rational basis review because of the extreme degrees of overinclusion and underinclusion); Bierkamp, 293 N.W.2d at 584 (finding the Iowa guest statute does not rationally further the legitimate state purpose of preventing collusive recoveries from insurance companies); Fed. Land Bank v. Arnold, 426 N.W.2d 153, 157 (Iowa 1988) (holding discrimination in redemption periods violated the equal protection clause where class membership did not correlate with purported class distinctions drawn by legislature); Chicago & N.W. Ry. v. Fachman, 255 Iowa 989, 997, 125 N.W.2d 210, 214 (1963) (“It is often said a reasonable classification is one which includes all who are similarly situated, and none who are not.”); Dunahoo v. Huber, 185 Iowa 753, 756, 171 N.W. 123, 124 (1919) (finding statute violated state constitution because classification made by legislature was unwarranted “where the evil to be remedied relates to members of one class quite as well as to another”).
Accordingly, I would find the statute unconstitutional under the equal protection clause of the Iowa Constitution.
HECHT, J., joins this dissent.