The small 16th century church of San Giovanni Battista Decollato (St John the Beheaded) belongs to the Arciconfraternita della Misericordia, also known as the Arciconfraternita di San Giovanni Decollato(Archconfraternity of St John the Beheaded), a charitable body whose mission was to save the souls of criminals sentenced to death.
Dressed in long black cloaks and black hoods, members of the confraternity would accompany the condemned from the prison to their place of execution, entreating them, all the while, to repent.
The executed were given a proper funeral and interred in one of seven common graves in the church's cloister. An inscription proclaims: DOMINE CVM VENERIS IVDICARE NOLI NOS CONDEMNARE (Lord, when you come to judge, do not condemn us).
The Arciconfraternita della Misericordia was founded in 1488 and in 1490 Pope Innocent VIII (r. 1484-92) granted it the church of Santa Maria della Fossa, with a duty to rebuild it.
Interior
The new church, with its dedication changed, was completed by 1504, but the interior decoration wasn't finished until 1580 or so. The church has a single nave with side altars, three on each side. The painting of the Beheading of St John (1553), above the high altar, is the work of Giorgio Vasari (1511-74).
In 1540 the Arciconfraternita della Misericordia was given the right, once a year, to set free a criminal sentenced to death. This right was exercised on August 29th, the feast day of the beheading of St John the Baptist, the confraternity's patron saint.
Michelangelo (1475-1564), who lived in Rome for much of his adult life, was a member of the confraternity.