He was the son of Thomas Weir, Laird of Kirkton, and his wife Lady Jean Somerville who was reputed to possess clairvoyant powers.
Major Weir, now in his seventies, continued to expand on his confession and Grizel, having seemingly entirely lost her wits, gave an even more exaggerated history of witchcraft, sorcery and vice.
She related how many years before a stranger had called in a "fiery" coach to take her brother to Dalkeith and how during the short trip another man had given him "supernatural intelligence" (Chambers) of the Scots' defeat at Worcester that same day.
Grizel maintained that Weir derived his power from his walking stick, topped by a carved human head, giving rise to later accounts that it had often been seen parading down the street in front of him.
Shortly before his end Weir had made a further public confession of incest with his sister, who was executed by hanging at the Grassmarket gibbet.
[11] The story of Weir has been proposed as an influence on Dr Jekyll and Mr Hyde, by Robert Louis Stevenson.
[12] The 2000 novel The Fanatic by James Robertson features Weir as a character and uses the events surrounding him as a central aspect of the novel's narrative and themes.