Utah's child sex-abuse laws should be amended to make it less likely that convicted child molesters like Allan B. Hadfield can elude prison terms, an assistant Utah attorney said Monday.

"Our only option is to change the legislation to avoid abuses like this," said Robert N. Parrish, the man who successfully prosecuted Hadfield for abusing and sodomizing two of his children.Parrish made that comment in reaction to Monday's Utah Supreme Court decision upholding Hadfield's sentence to six months in jail and 10 years probation. Although Utah laws provide for mandatory sentences of 10-years-to-life for sodomy on a child, 4th District Judge Cullen Y. Christensen ruled that Hadfield met each of 12 criteria necessary to qualify for probation under an incest exception to the mandatory sentencing guidelines.

In response, Parrish took the unusual step of challenging the sentence under a provision known as a writ of mandamus, which allows prosecutors to challenge sentences when judges overstep their authority.

But a three-member panel of justices refused to agree with that argument.

"Mandamus only permits review for extreme abuses of discretion amounting to arbitrary and capricious action," the justices said in a four-sentence ruling. "Here, any fact-finding error by the trial judge does not rise to that level."

Bradley P. Rich, attorney for Hadfield, was jubilant.

"I am not surprised because I didn't see the Supreme Court wanting to get involved with this tar baby," Rich said. "It means that Allan can do his six months in jail and engage in all other conditions of probation without the fear that it will be taken away."

He said the decision will, to some extent, put Hadfield's mind at ease.

"I'll tell him we won this battle and now he gets a chance to prove himself through his ongoing compliance with the terms of probation," Rich said.

The question that concerned the justices during Monday morning oral arguments was not whether Hadfield deserved what he got, but whether Christensen had sufficient basis for his ruling. Parrish contended there was no evidence to support the judge's ruling that Hadfield qualified under five of the 12 criteria. The judge's findings on those five counts, Parrish argued, constitute an abuse of "judicial discretion," a term that designates the vast latitude a judge has in deciding certain matters.

But the Utah justices did not find Christensen's ruling to be completely without basis, as Parrish claimed. Thus, they found the mandamus writ was unfounded.

Parrish said he was disappointed, though not surprised, with the court's refusal to review the sentence.

"I can't imagine a case where a lack of following the statute would be any clearer," Parrish said. "So what the court is essentially saying is that the judge's decision is beyond review."

Parrish said, however, that he will approach lawmakers in the next legislative session with suggested changes in the law, which was passed several years ago to provide minimum mandatory sentences for certain sexual offenses involving children.