A doctor is not held guilty of negligence if
Professional negligence: The failure to exercise reasonable care and skill of an ordinary prudent medical practitioner in the circumstances; a breach of duty to act with care appropriate to the situation, which resulted in bodily injury (harm/loss) or death of the patient.
He has exercised reasonable care and skill
He has not obtained informed consent from patient
He fails to give proper instructions
Others sufferer disease from his patient
Medical Jurisprudence