A deeply divided Brooklyn appellate panel has overridden a jury’s murder verdict and replaced it with a manslaughter conviction in a case involving a deeply troubled defendant who beat his fiancee to death with a baseball bat in what the court’s majority described as a “barbaric frenzy.”

The Appellate Division, Second Department, majority said the Westchester County jury’s unanimous decision in the Robert Sepe case was against the weight of the evidence. It invoked its powers as a “13th juror” to enter a verdict counter to the one reached by the jury.