The state Supreme Court is considering whether an expert in a medical malpractice case must be certified in the same specialty as the defendant or needs only practice in a similar field.

The court heard arguments Thursday in an interlocutory appeal from a trial judge’s order that took the broader view.

The case, Nicholas v. Mynster, A-6/7-11, turns on an interpretation of the 2004 Medical Care Access and Responsibility and Patients First Act, N.J.S.A. 2A:53A-38 et seq., which put strictures on expert’s qualifications.

The plaintiff, Edward Nicholas, collapsed while using a gas-powered cutting machine in a friend’s basement. He was rushed to South Jersey Regional Medical Center in Vineland, where Dr. Christopher Mynster, a specialist in emergency medicine, diagnosed him as having carbon monoxide poisoning. He was admitted by Dr. Rekha Sehgal, a family practice specialist, who put him on 100 percent oxygen through a mask.

Nicholas sustained brain damage and sued for malpractice. He retained as an expert witness Dr. Lindell Weaver, a certified specialist in internal medicine with a subspecialty in critical care and pulmonary medicine. In his affidavit of merit, Weaver said Nicholas would not have sustained brain damage had he been treated with hyperbaric oxygen.

Mynster’s lawyer, Mary Ann O’Brien, objected to the affidavit of merit. “The statute is very clear,” she said at Thursday’s argument. “An expert witness must be certified in the same specialty.”

O’Brien, of Absecon’s Crammer, Bishop & O’Brien, said Weaver would have to be a specialist in emergency medicine, although Mynster may have been engaging in other fields while working as an emergency room doctor.

“Are there other specialties that provide the same treatment?” asked Appellate Division Judge Mary Cuff, temporarily assigned to the court.

“That could very well be,” O’Brien conceded. But she restated her position that the Patients First Act is clear in requiring that an expert be certified in the same specialty as the defendant.

Sehgal’s lawyer also objected. “Dr. Weaver is not certified in family medicine,” said Karla Donovan, of Princeton’s Buckley Theroux Kline & Petraske. “He conceded he did not know how the average family practitioner would treat someone like the plaintiff.”

Justice Barry Albin asked what qualifications Weaver would need.

The same specialty as the defendant, Donovan said. “The purpose of the statute is to weed out frivolous lawsuits.”

Nicholas’ attorney, E. Drew Britcher, told the court that there should be no reason to disqualify Weaver because was an expert in those areas of medicine at least in terms of how Nicholas was being treated.

“A pre-eminently qualified individual should not be barred from testifying,” said Britcher, of Britcher, Leone & Roth in Glen Rock. He said the purpose of the Patients First Act was to ensure that nonqualified physicians could not be used as experts.

Presiding Appellate Division Judge Mary Cuff, temporarily assigned, asked whether it was permissible for there to be some type of “omnibus expert.”

“There was clear overlap” in Weaver’s field and the areas in which Mynster and Sehgal were practicing at the time, Britcher replied affirmatively. “This was critical care medicine. To bar him from testifying would not serve the purpose of the statute.”

Justice Helen Hoens asked how Weaver’s specialties could be used to justify his affidavit of merit against Sehgal, a family practice specialist.

“This was not office-based family medicine,” Britcher said. “She was not practicing family medicine at that time.”

“How does that square with the statute?” Cuff asked.

“Doctors with overlapping specialties are not precluded from testifying,” Britcher said. “He is particularly qualified to treat that condition. That is what the Legislature intended.”