John Kincaid was a firm believer and a brave man. He was also trying to make a name for himself, in hopes of being noticed by the Lord Protector.
He was responsible for deaths of many people he convicted. Kincaid's preferred evidence was a confession of the accused, and he did not hesitate to use torture to achieve such a confession. However, causing pain was not his objective. If he could achieve a "confession" by misinterpreting the victim's words, he would stop the torture at once.
He was called to Tranchard's Fell by the village squire Claude Portillon to investigate five bodies murdered in an unnatural way. There he tortured the Eighth Doctor and sentenced him, Agnes Bates and Beatrix Butcher to death for witchcraft.
His meddling with the WitchStar, a Veraxil artefact, was responsible for turning Agnes into a bloodthirsty witch. Thus, he was indirectly responsible for the carnage that she caused in the village. He volunteered to accompany the Doctor to Vetter's Tor on a mission to find a way to subdue the witch. There he confronted her and was slain. (AUDIO: The Witch From the Well)