Recognizing for the first time an exception to its strict vacatur standard, the Appellate Division, First Department, yesterday vacated a lower court evidentiary ruling favoring a police detective under disciplinary charges who resigned before the City’s appeal of the ruling was decided.

The four-judge panel in In re Ruskin v. Safir unanimously granted the City of New York’s motion to vacate Acting Justice Louis York’s June 18, 1998, order holding that the testimony of certain witnesses was inadmissible at a Police Department disciplinary hearing against Detective Thomas Ruskin. Mr. Ruskin’s resignation had deprived the department of its opportunity to win a reversal of the order in his favor, the court said.