Unlike medical malpractice cases where it is usually required to have an expert opinion to file a lawsuit, there is no such requirement for legal malpractice claims. However, in many cases, it is advisable or even necessary to have an expert witness for your legal malpractice case. An expert witness in a legal malpractice case will provide an opinion as to the applicable standard of care in your underlying legal matter -- what your attorney should have done in your case or legal matter -- and how your attorney’s conduct fell below this standard.