Medical expert witnesses provide consultation and testimony for a very wide range of issues, including medical disorders, medical treatment, doctor, nurse and facility standards of care and conduct, malpractice, forensic medicine, misdiagnosis, delayed diagnosis, birth injury, and pathology. In most cases, the law requires that virtually all medical malpractice cases must be proven with medical expert testimony. Generally, the type of expert to be retained must be a physician who practices in the same specialty as the accused doctor; because most physicians will not testify against other physicians in the same state in which they practice, most testifying experts are from out of state.