P sought treatment for back, neck, and arm pain from Chappuis (D) who prescribed a 30-day regimen of the anti-convulsive drug Tegretol, followed by another 30-day regimen when her condition had not improved. Shortly after the second prescription began, P started experiencing leg cramping and shortness of breath, leading ultimately to her hospitalization, where she was diagnosed with aplastic anemia, a rare and serious bone marrow disease. P sued Ds for medical malpractice. At trial, P's experts and treating hematologists opined that the Tegretol had caused the disease and it could have been avoided if D had conducted blood count monitoring during P's treatment. D's experts acknowledged at trial that much of the medical literature recommends blood count monitoring during Tegretol therapy the standard of care did not demand it. During pretrial discovery, one expert had deposed that it was his usual practice to conduct blood count monitoring when he prescribed Tegretol. Before trial, D moved in limine to prevent Ps from inquiring at trial into these experts' personal practices, and the trial court granted the motion. D got the verdict and P appealed. The Court of Appeals affirmed. The Court of Appeals upheld the trial court's decision to exclude such testimony by relying on the controlling authority of Johnson v. Riverdale Anesthesia Assocs., 275 Ga. 240 (563 SE2d 431) (2002). P appealed.