DETROIT — Plaintiffs in a federal court challenge of Michigan’s ban on same-sex marriage have filed a brief seeking to ban the author of a discredited study on gay parenting from testifying as an expert witness on behalf of the state.

In their motion, the plaintiffs’ attorneys say University of Texas sociology professor Mark Regnerus’ 2012 study was based on “flawed methodology,” was rejected by hundreds of scholars as well as the American Sociological Association, and that he is not qualified to testify on the issues in the case.

From the brief:

Mark Regnerus, Defendants’ purported expert, fails to meet the minimum requirements imposed by the Federal Rules of Evidence. His flawed methodology and generic conclusions, untethered to any of the specific factual issues in this case, render his opinion unreliable and irrelevant […] In addition to being relevant, an expert’s testimony must also be reliable. Reliability of an expert’s conclusions is based on the expert’s knowledge or experience in his or her discipline, rather than on subjective belief or unsupported speculation. On its face, Regnerus’s expected testimony fails to address defendants’ three other asserted justifications for the Michigan Marriage Amendment because he does not discuss (1) the effects of redefining marriage, (2) the tradition or morality of marriage, or (3) transitioning “naturally procreative relationships into stable unions.”

Since its publication, the Regnerus study has been cited by anti-gay rights activists in marriage equality and LGBT adoption debates both in the United States and internationally.

The University of Central Florida, which houses the publication that originally published Regnerus’ report, is currently engaged in a legal battle to block the release of over 50,000 documents related to the flawed study.

The lawsuit challenging Michigan’s same-sex marriage ban is scheduled for trial on Feb. 25.