In 1623, a Moluccan soldier named Alexo de Castro was arrested by authorities of the Holy Office of the Inquisition in Manila. Denounced by his wife, Ynés de Lima, for secretly observing the Muslim faith in Manila, Castro faced inquisitorial investigations that initially were inconclusive. Alexo de Castro was released. Two decades later, Ynés de Lima and her slave María de Lima denounced Alexo de Castro for secretly observing Islam in Manila, for sexually abusing women in his household, and for making heretical statements regarding fornication. Considering this alleged crypto-Muslim a threat to Christianity society, inquisitors sent him to Mexico City, the seat of the inquisitorial district of which the Philippines was a part, for trial. Castro was ultimately tried, found guilty, and sentenced to perpetual confinement in a monastery in Mexico City for the remainder of his life.

The Inquisition trials of Alexo de Castro are valuable to the history of the early modern Hispano-Asian Pacific world on several levels. In institutional terms, the case is entirely unique: the Comissariat of the Inquisition in Manila was a branch of the Holy Office that reported to the Tribunal of the Inquisition based in Mexico City, which throughout the early modern period retained its exclusive authority to conduct trials and issue sentences. The fraught logistics of the transpacific galleon links between the Philippines and Mexico all but guaranteed that very few inquisitorial prisoners would ever be sent to Mexico for trial.