Who should you seek for a medical diagnosis your primary or Dr.of Internal Medicine for Pernicious Anemia?

THIS IS OF UTMOST IMPORTANCE. My son had a psychotic break and we had his primary do tests. B12 deficiency was found and this could be cause of psychosis. He was violent and could go to prison. He is a good person and we know there has to be a medical reason that we must find and prove for his defense as well as his healing. He is on anti-psychotic medicine.