PORTLAND – A York County probate judge faces possible disbarment or suspension after an oversight panel found that he engaged in unethical behavior by having a sexual relationship with a client while handling her divorce in 2003.

Robert Nadeau of Kennebunk must appear before the Maine Supreme Judicial Court to defend his license to practice, but no hearing date has been set.

Last week’s decision is the latest accusation against Nadeau, who also runs a law firm in Wells. Although probate judges are elected, Nadeau would lose his position if he is disbarred by the state supreme court, County Manager David Adjutant said.

Nadeau is serving his third term as a York County Probate Court judge. In that position, lawyers may continue private practice on days they do not work as judges.

His attorney, Stephen Wade, said the bar overseers’ decision was preliminary and Nadeau still hopes the state’s highest court will rule in his favor.

“He doesn’t agree with the decision,” Wade said, adding that none of the allegations against his client arose from his service as a judge.

The bar overseers sifted through e-mails and other correspondence that detailed a relationship between Nadeau and client Lynnann Frydrych, then known as Lynnann Sciulli, before reaching its conclusion.