ATLANTA—A plaintiff who slipped and injured herself on a cruise ship is entitled to submit expert testimony to determine the adequacy of the vessel's flooring surface in a new trial, a U.S. appeals court ruled last week.

Lydia Rosenfeld, who slipped and fractured her shoulder while aboard the M/V Nautica, was precluded from using expert testimony to determine the slip resistance of the ship's flooring surfaces, according to court documents.

The expert testimony was provided by Peter Vournechis, a floor-safety specialist who performed various tests on the slip resistance of the floor and determined that, under wet conditions, the ceramic tile surface surrounding the buffet area of the vessel had a “low coefficient of friction” and was not reasonably safe, according to court documents.

Ms. Rosenfeld sued Miami-based Oceania Cruises Inc., operator of the vessel, for medical damages, claiming that Oceania negligently caused the accident by failing to provide an adequate flooring surface for the buffet area where she fell.

A lower court said the plaintiff “has not established that the proposed liability expert will provide helpful analysis to the court in understanding a matter of scientific, technical or specialized expertise,” court documents said.

But a three-judge panel of the United States Court of Appeals for the Eleventh Circuit in Atlanta disagreed, stating that Ms. Rosenfeld's principal theory was that Oceania's choice of tile was unreasonable and that a qualified expert using reliable testing methods may testify.

“We cannot say that the district court's error was harmless. Because Rosenfeld was not allowed to admit evidence proving the inadequacy of Oceania's choice of flooring surface, the jury could not have found that the floor near the Terrace Café's buffet was necessarily unsafe when wet,” Judge Charles R. Wilson wrote in the opinion. “Consequently, the jury was not able to consider whether Oceania's choice of ceramic-tile flooring caused Rosenfeld's injuries.”

The ruling was reversed and the judges concluded that a new trial is warranted.