Cardinal Roger M. Mahony, seen in this Sept. 22, 2007, file photo, is among those being investigated by a federal grand jury to determine whether he failed to keep children safe from predatory priests.

Los Angeles ? A federal prosecutor with a penchant for applying the law creatively is taking on the nation’s largest Roman Catholic Archdiocese in a child molestation case that could break ground for prosecuting high-ranking church officials.

But legal experts questioned whether U.S. Attorney Thomas P. O’Brien could persuade a jury that by allowing the molestation of hundreds of children by Catholic priests church leaders violated the federal “honest services” fraud law.

The law, which makes it illegal to scheme to deprive others of their right to honest services, has most often been used to prosecute politicians and chief executive officers of corporations. It has never been used against a church.

The Los Angeles Times, citing unnamed sources, reported Thursday that O’Brien was pursuing the honest services fraud strategy.

He would have to show that parishioners were denied the honest services of Cardinal Roger M. Mahony and other church leaders. A federal grand jury is investigating how they handled their internal investigation of child-molest allegations brought against Catholic priests.

The Archdiocese reached a record $660 million settlement in 2007 with more than 500 alleged victims of child abuse.

Laurie Levenson, a professor at Loyola University Law School and a former federal prosecutor, predicted the honest services fraud would be difficult to prove because it requires evidence of “a specific intent to defraud.”

“Federal statutes are designed to cover a myriad of kinds of behavior, but just because you can charge them doesn’t mean the jury is going to convict,” Levenson said.

Mahony said the Archdiocese was cooperating, but he thought the matter had already been laid to rest by previous state and local investigations.

“Basically we were mystified and puzzled by the whole thing,” Mahony told Los Angeles radio station KNX on Thursday. “We have been through these investigations for years now.”

One legal expert seemed to agree, suggesting a federal prosecution was unwarranted.

“It’s outrageous that they’re in it,” said G. Robert Blakey, a professor who teaches federal law at Notre Dame University and who helped draft the honest services statute.

“What does this have to do with the federal government?” Blakey asked. “The state of California has prosecuted many cases. They got a huge settlement in civil cases. Why is the federal government doing it now? Doesn’t he (O’Brien) have enough to do with terrorists, with financial fraud, with drug smuggling?”

The U.S. attorney’s office said Thursday it would have no comment.

O’Brien gained attention last year when he stepped in after local authorities declined to prosecute a Missouri woman for allegedly causing the suicide of a teenage girl through an Internet hoax. Authorities said Lori Drew created a phony MySpace profile for a teenage boy and used it to flirt with the girl, then dump her.

O’Brien brought computer fraud charges under a law normally used in hacking and trademark infringement cases. Drew was convicted of minor charges of using computers without authorization, but she was acquitted of more serious crimes.