A man who was expected to plead guilty yesterday to having sex in St. Patrick’s Cathedral will have to answer to a higher authority.

Brian Florence, 38, died of a heart attack Thursday in Alexandria, Va., his lawyer announced yesterday in court – surprising the judge and prosecutors.

The news forced Manhattan Criminal Court Judge Barbara Jaffe to adjourn the case against Florence and girlfriend Loretta Harper, 36. The two were arrested inside the cathedral after being caught in the act as part of a radio show stunt.

“We’re told that it was heart failure. It was very sudden. The family is still in a state of shock,” defense lawyer Maranda Fritz said outside the courtroom. She said Florence was buried Monday.

The couple had been expected to plead guilty to disorderly conduct.

Earlier yesterday, a third man involved in the sexcapade, radio producer Paul Mercurio, 43, pleaded guilty to disorderly conduct and got seven days of community service.

The sex act by Harper and Florence inside St. Patrick’s outraged the city and led to the firing of WNEW shock jocks Opie and Anthony, otherwise known as Gregg Hughes and Anthony Cumia, who allegedly put them up to it.

The couple was discovered by an usher who thought Florence was urinating, until he approached him and saw Harper naked from the waist down. The scene was visible to about 20 worshipers and tourists.

Mercurio admitted providing the live on-air commentary describing their actions and offered a mea culpa.

“Since the show, I realized how inappropriate these actions were. I have apologized personally to monsignors at St. Patrick’s Cathedral and apologize publicly now for the disrespect we showed the church, its parishioners and the people of the City of New York,” he said.