Florence, March 6 - A new documentary about priest sex abuse is opening in Italy around the time that cardinals are convening in Rome to elect a new pope. Oscar-winning documentarian Alex Gibney's new film Mea Maxima Culpa: Silence in the House of God premieres in Florence March 18. The hard-hitting documentary about the Vatican's record on managing child-abusing priests spans decades and continents, beginning in Milwaukee, Wisconsin, where Father Lawrence Murphy is believed to have abused up to 200 schoolboys as head of the St John's School for the Deaf. Gibney and his production team also look into the headline-grabbing Irish case of Tony Walsh, a convicted serial abuser of both sexes who preyed on children at funerals, and the way the Vatican hushed up the sex crimes of Mexican priest Marcial Maciel, a senior associate of Pope John Paul II, before sending him to retire in a Florida mansion. The film hits movie theaters nationwide on March 20. Cardinals are currently in Rome ahead of the conclave to elect a successor to Benedict XVI, who stepped down last week. They have yet to announce a date for the start of the conclave. Advocacy groups have been pressuring cardinals to make priest sex abuse - especially of children - a central focal point when considering candidates for the new pontiff.