In the late summer of 1678, Margaret Anderson was caught in the legal machinery of the Scottish judiciary amidst a broader series of witch trials that drew in residents from across Crichton and Humbie. Although historical documentation reveals a degree of geographical fluidity regarding her residence—placing her variously in the Birnstown area near the Birns Water in Humbie, as well as in the nearby parish of Ormiston—Margaret was officially summoned to answer for her actions in the capital. The proceedings against her were formalized under the reference C/EGD/689, which brought her case into the purview of the central courts in Edinburgh.
On the 13th of September 1678, the date set for her trial under records T/LA/1434 and T/LA/834, Margaret did not appear to answer the charges. In the legal parlance of the seventeenth century, her absence resulted in her being formally declared a fugitive. Consequently, she was "put to the horn," a process of outlawry involving the symbolic blowing of a horn at the Mercat Cross, which signaled that she had moved outside the protection of the law and remained a person of interest to the state. Beyond this act of non-appearance, the surviving records remain silent on her subsequent movements or ultimate fate.