Rupert Murdoch’s attempt to change his family trust to consolidate his son Lachlan’s leadership of his global media empire — and lock in its conservative editorial direction after his death — now depends on a long-shot move in the highly specialized Nevada probate court system.

The first step for Mr. Murdoch is to try to convince a district court judge in Reno to reject a local commissioner’s harsh ruling this month that he had acted in “bad faith” when he moved secretly to change the trust that left control of his empire divided equally among his four oldest children. Mr. Murdoch’s brief challenging that opinion is now due December 23.

If Mr. Murdoch fails, and the commissioner’s recommendation is ratified by the judge, his lawyers have said that Mr. Murdoch will appeal the probate court’s decision. Under the Nevada system, that appeal would be filed directly to the State Supreme Court.

To prevail, Mr. Murdoch, 93, will have to clear a high legal bar — proving that the Nevada probate commissioner’s finding of bad faith was “clearly erroneous,” according to the rules of the Reno-based court circuit.

“These types of decisions are not that easy to challenge because of this ‘clearly erroneous’ standard,” said Kevin P. Walsh, a Nevada estate planning and litigation lawyer who appears regularly in the Reno probate court. “It would have to be something that really slaps you in the face as being a mistake.”

That might prove especially difficult, he said, because of the breadth and unequivocal language of the Dec. 7 recommendation that the probate commissioner, Edmund J. Gorman, filed under seal this month.