Beginning in early 1628 and continuing for several years, a series of witch trials, leading to hundreds of executions, was in process in Mergentheim, and Thomas Schreiber became known to be in opposition to it.
He referred to the witch trials as a bloodbath and stated that he suspected that the city authorities wished to "wash their hands in my blood".
On 10 April, a joint letter of protest against his arrest signed by friends in Heidenheim, Langenau, Ellwangen, Dinelsbuhl and Aalen was delivered to Mergentheim, in which they protested against the fact that Schreiber had been arrested without any specific accusations, and that he might have sinned by criticizing the court, but that leniency was warranted because of his youth and minor children.
The interrogators stated that the witch trials were the justice of God and encouraged him to confess his guilt, but he called the whole legal process an injustice, called the 34 witchcraft executions that had been conducted since his arrest a bloodbath, and stated to the interrogators: "As truly as Christ died on the cross and God created me, I am innocent.
[1] During the following torture, he confessed that he committed adultery with Satan in the shape of a woman and that he had become a witch for the sake of sex rather than to perform magic; that he had stolen and desecrated the sacramental bread; that he had attended the witches' Sabbath and that he was since then unable to pronounce the rosary; and finally, he denounced seven accomplices he had purportedly seen attending the Sabbath with him.
He reminded her that she had often said to him that "whoever is chosen for eternal life must undergo thistles, thorns and strife"; that he wished for her to marry again, "on account of the children, for widows and orphans are despised and pushed down in this vile world",[1] and assured her that he was innocent and that they would meet again in heaven.
Anna Schreiber wrote back and replied that she asked his forgiveness if she had ever given him the impression that she believed the accusation against him, and that she wished that she was dead herself.