The German prosecutions of the 1620s are the immediate setting for the sharpest attack on witch trials written anywhere in Europe. Friedrich Spee, a Jesuit, served as confessor to the condemned in these years and published the Cautio Criminalis anonymously in 1631.
Read against Würzburg, the book stops being an abstract argument. Spee is describing what he had watched: that torture produces agreement rather than truth, that the confessed must name others and so the arrests never stop, that denial is punished, confession is fatal and retraction brings more torture. When he writes that he does not believe he ever accompanied a guilty person to the scaffold, he is talking about people who had been priests and children in his own territory.
He is also making an argument the judges could not answer. If the procedure would convict an innocent person with exactly the same certainty that it convicts a guilty one, then the verdicts carry no information at all, whatever the truth about witches may be. Spee explicitly declines to say there are none.
Prosecutions in the prince-bishopric fell away in the 1630s. Several things were happening at once, including the war, the arrival of Swedish forces, and the death of the ruling prince-bishop, and the honest position is that Spee's book is one factor among them and its weight cannot be isolated.