SAN FRANCISCO — For Morgan, Lewis & Bockius and one of its former patent attorneys, the alleged cover-up could be worse than the crime.

On Monday the U.S. Court of Appeals for the Federal Circuit reinstated a fraud claim against the law firm and Thomas Kohler, who now practices at a midsize firm in Vermont. The Federal Circuit ruled that while the statute of limitations had run on malpractice for a patent filing error, client Landmark Screens LLC had preserved its rights by adding a claim for actual fraud over alleged concealment of the error.