In the Sister Wives case (Brown v. Buhman), a family featured in a reality TV show and non-fiction book about their family, is religiously and ceremonially polygamous, but does not claim to have more than one civil marriage, brought suit to invalidate Utah's bigamy statute. Utah's bigamy statute, like Colorado's bigamy statute (but unlike the bigamy statutes of most other states), bans not only marriage to more than one person at a time, by cohabitation of a non-spouse with an opposite sex married person.
The Sister Wives family brought suit in federal court in Utah to have the cohabitation clause of the statute declared unconstitutional, while not seeking to invalidate the bigamy clause barring more than one civil legal marriage at a time and without seeking to require the State of Utah to recognize that they have a legally valid plural marriage.
The State of Utah did a miserable job litigating the case in the trial court, where it lost. The trial court decision on the merits that is appealed from (after a preliminary standing issue was resolved) is here and was previously discussed at this blog.
The State of Utah is trying to raise new issues and to insert a few more facts into the discussion that were not raised in the trial court in its opening brief on appeal in the 10th Circuit Court of Appeals. The Sister Wives family has now filed an answer brief addressing the state's claims and issues raised in some of the numerous amicus briefs filed in the case. Once the State of Utah files its reply brief in several weeks, the 10th Circuit will probably set the case for oral argument, probably sometime late this year, after which a three judge panel will decide who wins and write an opinion, realistically, sometime next year.
All of the doctrines appellate procedure in civil cases, that prevent parties from introducing new facts, or raising new legal arguments, on appeal, along with developments in constitutional law over the last decade and a half, most notably the Lawrence case decided by the U.S. Supreme Court in 2003, which held that a law banning sodomy between consenting adults was unconstitutional, should make it easier for the 10th Circuit to affirm the lower court than it might otherwise have been.
But, given the politically charged nature of any ruling finding that a polygamous family is entitled to any sort of constitutional protections, the Sister Wives family, like any reasonable litigant in their shoes, can take nothing for granted.
Also, a ruling affirming the trial court decision on procedural grounds might be less useful as a precedent in other cases, although a ruling driven by procedural considerations might also make it easier for the U.S. Supreme Court to decline to review a 10th Circuit ruling in the case.