Ex-Pope Benedict's failing health presents difficult decisions for Vatican

The Catholic Church has strict protocols in place following the death of its leader, but as ex-Pope Benedict's health wanes it is unclear whether those same protocols will apply to a retired pope, known as Emeritus.

When Benedict XVI resigned in 2013 citing old age, he became the first pope in 600 years to step down from the role. Born Joseph Ratzinger, the German cardinal was elected in April 2005 and chose to go by the name of Benedict.

For almost a decade there have in effect been two popes living at close quarters in the Vatican, because Benedict has stayed in the Vatican Gardens at the Mater Ecclesiae monastery and appeared occasionally alongside his successor.

"We've never had this before where a living pope will help bury a dead pope," Catholic historian John McGreevy said.

Even the Middle Ages do not provide a template, because when Gregory XII resigned in 1415 his aim was to bring an end to years of division involving rival challengers to the papacy.