Margaret Roger confessed at the same time as her sister Janet. Margaret was around sixty years old, and like her sister, was a poor woman. Her testimony was particularly damning for the accused Margaret Lang, as she claimed that Lang had introduced her to the devil three years previously, in the gloaming. The devil assured her that she would not want for anything, but Margaret declared that he never gave her anything. He did, however, give her the name Swiftfoot. Margaret admitted to being at several meetings with the devil in the company of the other accused individuals in the yard of Bargarran House, as well as at various other alleged crime scenes in the local area.

Margaret, like the rest of the accused, was subjected to the skills and experience of the witch pricker. When she gave herself to the devil, she admitted that he had left his mark on her thigh. This was presumably where the pricker found his evidence. Margaret’s confession came relatively late on in relation to the period of investigation, but, like her sister’s, it proved telling. When combined with the confessions of Elizabeth Anderson and the Lindsay brothers, her evidence provided a greater degree of corroboration that would have strengthened the case of the prosecution during the trial, and made it easier for the jury to reach a unanimous verdict against the majority of the accused.