Sec. 12. TRANSFER OF DUTIES OF JUSTICE OF PEACE. When the commissioners court of any county shall establish the office of medical examiner, all powers and duties of justices of the peace in such county relating to the investigation of deaths and inquests shall vest in the office of the medical examiner. Any subsequent General Law pertaining to the duties of justices of the peace in death investigations and inquests shall apply to the medical examiner in such counties as to the extent not inconsistent with this Article, and all laws or parts of laws otherwise in conflict herewith are hereby declared to be inapplicable to this Article.