A state appeals court on Tuesday overturned a $500 Special Civil Part judgment because the judge crossed the line into advocacy in his questioning of unrepresented litigants.

Passaic County Superior Court Judge Bruno Mongiardo’s “domination” of the proceedings prevented the parties from fairly presenting evidence and from cross-examining each other and a nonparty witness, and “left the factual underpinning of the claims and defenses in doubt,” the panel said in Mastropole v. Giunta, A-1266-10.

“There is a point at which a judge may cross that fine line that separates advocacy from impartiality. When that occurs there may be substantial prejudice to the rights of one of the litigants,” the panel said, directing that the case be assigned to a different judge on remand.

The case was a dispute over alleged an alleged purchase of a trailer that was never delivered. Buyer Joseph Mastropole claimed that he gave $1,600 to seller Benjamin Giunta through a third party. Giunta claimed there was no contract between him and Mastropole.

Mongiardo began the trial by saying to Mastropole, “let me take your testimony.” When Mastropole started to speak, Mongiardo interrupted and asked “a multi-part, leading question” about the transaction details, the appeals court said.

The judge then asked Giunta, “‘what would you like to say in response to all this?” Giunta turned to Mastropole and asked what date he first looked at the trailer. Mastropole began to respond, but Mongiardo cut him off and began asking his own questions.

Giunta then tried to ask Mastropole whether he had ever telephoned him, but the judge again cut off the questioning and asked his own questions of Giunta.

According to the appeals court, which characterized the details as “muddled,” Giunta said he did not release the trailer to Mastropole because the third party, Anderson, Reed had negotiated to buy the trailer for $500, which Giunta later admitted receiving.

Mastropole said he tried to pick up the trailer three weeks after paying for it, only to be asked to pay $300 to Giunta for storing it, which he refused to do.

One of Giunta’s appellate attorneys, Marissa Quigley of Lite DePalma Greenberg in Newark, says that after Reed negotiated to buy the trailer for $500 from Giunta, Reed made a second deal to sell it for $1,600 to Mastropole.

Mastropole brought a criminal complaint against Giunta, who was charged with theft by failure to make a required disposition of property. Giunta said he pleaded guilty to a disorderly persons charge in that case.

Mongiardo, finding no proof of the $1,600 payment, entered judgment for $500 in restitution against Giunta.

On appeal, Giunta claimed that Mastropole had no standing to sue because they had no contract.

Appellate Division Judges Marie Lihotz and John Kennedy said they could not review that issue because it was never formally presented to the trial judge.

But the appeals court concluded that the trial was “not fairly conducted.”

While conducting a bench trial with self-represented litigants is challenging, a judge must take special care to avoid being perceived as an advocate, the judges said, noting that Mongiardo essentially asked all the questions, affording the parties no chance for cross-examination.

“In this case, even before plaintiff had the opportunity to present his case, the judge prematurely and unnecessarily intervened and dominated the examination of the parties and the witness,” they said. “As the judge began to form conclusions about the facts, he, in effect, assumed the role of advocate in his questioning.”

In addition, it was unclear whether the parties had completed presentation of their cases by the time Mongiardo ruled, the appeals court concluded.

Bruce Greenberg, who with Quigley represented Giunta, says he’s “pleased we got a reversal for our client.”

Mastropole could not be located for comment.

Mongiardo, who declines comment, was appointed in 2009 by Gov. Jon Corzine and is up for tenure in 2016. He served as first assistant Passaic County prosecutor from 2002-09 and 1976-89. He was in private practice from 1989-2002 and a Passaic County deputy public defender from 1974-76.

In the Law Journal’s 2012 Superior Court Judicial Survey, lawyers rated Mongiardo 13th of 25 judges in his vicinage, with a score of 8.43 points out of a possible 10. His highest rankings were for lack of bias as to race, gender and party identity, 8.83; courtesy and respect to litigants and lawyers, 8.65; and prompt decision-making, 8.58. His lowest scores were for capably handling complex cases, 8.06, and skillfully fostering settlement, 8.08.