The Supreme Judicial Court of Massachusetts decided Monday that sexual relations between step-parents and their stepchildren are not considered incest and are therefore not criminally punishable.

In a controversial 4-3 decision, the court deemed the commonwealth’s incest laws inapplicable to step-parents due to “consanguinity,” or the blood-relation requirement of current Massachusetts law.

In the SJC’s majority opinion, Justice Robert Cordy wrote that “by its plain language,” state law “selects for criminal punishment those relationships listed in the marriage statute that are relationships of consanguinity.”

The commonwealth’s incest law states that “persons within degrees of consanguinity within which marriages are prohibited” who engage in sexual activity of any kind “shall be punished by imprisonment in the state prison” for up to 20 years.

Several dissenting justices concluded that the majority’s decision was invalid and ill-founded.

“It is self-evident” that legislators intended the incest law to include stepfamily relationships by “referring to, and incorporating, the marriage prohibition statutes,” wrote Justice John Greaney in his dissenting opinion.

In the case, 60-year-old Dawud Rahim was charged with incest after raping his stepdaughter. The court dismissed the incest charges but allowed two counts of rape to stand. The rape charge carries a maximum penalty of life in prison. Rahim was also charged with six counts of videotaping sex acts with his stepdaughter and six counts of wiretapping for recording the acts without consent.

Nancy Hathaway, the Suffolk County prosecutor in Commonwealth vs. Rahim, said she was “a little bit surprised” by the SJC’s ruling, though she noted that the court left the door open to legislators to change the incest law to include step-parents.

“The District Attorney’s Office is going to propose a legislative amendment to plug this gap in the law,” Hathaway added.

Hathaway recalled a case, Commonwealth vs. Smith, in which the nature of incestuous relationships was discussed. The Legislature immediately amended the incest laws to include different forms of sexual behavior but failed to include a statute that would incriminate non-blood relatives.

Because of this, “the defense [in Commonwealth vs. Rahim] had a legal argument to dismiss incest charges,” Hathaway said.

Wendy Murphy, a professor in the New England School of Law, said she was skeptical of the court’s decision and hopes the Massachusetts Legislature will amend incest statutes to include step-parents, though she believes that some legislators have misguided principles on this subject.

“Unlike when they amended the incest statute to include abuse other than intercourse, there might actually be a few ‘Woody Allens’ on the hill who think there’s some type of freedom in excluding step-parents from incest laws,” she said in an email. “Of course, this would be an endorsement of a kind of entitlement – not freedom – an entitlement of the worst kind where the powerful parent can exploit a trust position and cause harm to a vulnerable and dependent child. It’s terrible really.

“Incest [law],” Murphy continued, “is designed to prevent exploitation of the extraordinary power parents (and adults in parental positions) have over children. The point is to deter exploitation and punish those who take advantage of their power by harming the defenseless.”

Murphy cited a 1998 SJC decision involving child abuse in which the court said child abuse “is not limited to the abuse of one’s own child but means the abuse of any child,” despite no specific legal statute.

Based on that ruling, Murphy said the court should have ruled differently in Commonwealth vs. Rahim.

Critics of Monday’s decision, quoted in an Associated Press article, wondered why the SJC did not cite the “changing realities of the American family,” which was the basis for their November decision to authorize gay marriage.

Gay and Lesbian Advocates and Defenders, a pro-gay-rights legal organization, and the Coalition for Marriage, an anti-gay marriage, pro-traditional families organization, both declined to comment.