A judge in 5th District Court has denied a petition by polygamists Vaughn and Sharane Fischer to adopt the six children of a woman who died two months after becoming Vaughn Fischer's third wife.

Judge Dean Conder, in what could become a landmark polygamy case, ruled Monday that, "Polygamy is a crime . . . and the practice of polygamy constitutes immoral conduct."Conder further added that it is "not in the best interests of the children to be raised in such an atmosphere."

The Fischers, as well as the state Department of Social Services, had maintained that polygamy, like other religious practices, is not the issue in an adoption case. Rather it is ability and willingness of the adoptive parents.

In a home study report by the state Division of Family Services, a social worker determined the Fischers are "highly qualified" to adopt the six children.

The case involves children, ages 5 to 19, of Brenda Johanson Thornton, who died of cancer Aug. 17, 1987. Thornton had signed over custody of the children to the Fischers before her death and had requested they legally adopt the children.

But that adoption petition is being opposed by Pat and Janet Johanson, Brenda's two non-polygamous sisters, who maintain children should not be raised in an environment that has been deemed illegal by the courts.

Steven Snow, the Fischers' attorney, said he will appeal Conder's dismissal. While polygamy is illegal in Utah, Snow said, "there is no law banning a polygamous couple from adopting."

Conder ruled that Vaughn and Sharane Fischer will continue to have temporary custody of the children until appeals on the case have been exhausted. When asked how far he would appeal the judge's decision, Vaughn Fischer replied, "To the point of keeping our children."

The Fischers are residents of Hildale, Washington County, a polygamous community. The town neighbors Colorado City, Ariz., another polygamous community. Together, they are commonly referred to as "Short Creek."