Why did Justice Sandra Day O’Connor believe the Texas law violated equal protection?

In the case of Lawrence v. Texas, Justice Sandra Day O’Connor concurred with the majority that the Texas statute was unconstitutional, but she reached this conclusion based on the equal protection clause of the Fourteenth Amendment rather than the due process clause.1

Justice O’Connor argued that the law violated equal protection because it was discriminatory in its application. Specifically, she believed that a state may possess the authority to outlaw certain types of intimate sexual conduct, but it must do so in a nondiscriminatory manner. Because the Texas law targeted only same-sex couples while permitting identical behavior by different-sex couples, she found that it failed to satisfy the constitutional requirement of equal protection under the law. Unlike the majority, she did not base her decision on a broader right to privacy.1