Becoming a medical witness isn’t something you go to school for, well at least not directly. You cannot attend Medical Witness career college, and in order to become one you do need to have a strong medical background obviously.  This is why a lot of retired doctors will become medical witnesses. In fact, a group of doctors has actually started a company revolving around medical witnesses. They remain neutral, and lawyers come to them asking their opinion. Judges know that medical opinions coming from this company are valid and objective. The key is to be objective, because when a lawyer has a doctor on payroll that clearly is not an objective opinion.