What is the legal ruling regarding the death of a sick son who was treated with a poisonous plant, the toxicity of which was unknown to the mother and grandmother?

If the one who prescribed the medicine is known in medicine, then there is no harm in using the treatment, and no sin upon the grandmother or the female doctor. However, if she was ignorant of medicine and the grandmother believed her out of ignorance, then there is no sin or liability upon the grandmother. But the one who prescribed it must offer expiation (kaffarah) and blood money (diyah) based on the hadith: "Whoever practices medicine without being known to be a physician is liable." There is no retaliation (qisas) or blood money (diyah) upon a doctor merely for ordering a patient to drink medicine.