This rarely represented subject shows the martyrdom of the bishop of Csanád, Saint Gerard Sagredo. A Venetian by birth and venerated as the city's first martyr, Gerard, or Gellért as he is also known, became a monk and later a prior at San Giorgio Maggiore. On a pilgrimage to Jerusalem he travelled through Hungary where he educated King Stephen's son, Saint Emeric, and played a considerable role in converting the country to Christianity.
Johann Carl Loth trained in Munich under his father, Johann Ulrich, with whom he is first thought to have seen examples of seventeenth century Roman painting. In his early twenties he went to Italy, initially to Rome and then to Venice, where he had settled by 1656. He worked first in the studio of Pietro Liberi and then under Giovanni Battista Langetti, both of whom exerted a lasting influence on his art.
By 1677 Loth had begun work on an altarpiece depicting the Martyrdom of Saint Gerard Sagredo for the church of Santa Giustina in Padua. The present work, however, would appear to be a modello for another painting of the same subject, now in the Musée des Beaux-Arts, Strassburg. This sketch departs from the Padua composition in the addition of a further executioner, leaning over the fallen Saint, and with the dagger-bearing figure on the extreme left. Once thought to be by Pietro da Cortona, the dramatic lighting and unrestrained violence of the Strassburg picture show a clear debt to the art of the Roman Baroque.