In medical malpractice cases, the central issue is whether the defendant doctor had applied the degree of skill, knowledge, and care ordinarily exercised by other members of the medical profession under similar circumstances. Although this is left to the trial judge’s discretion, a physician or surgeon must usually have some occupational experience in the particular field at issue in order to testify as an expert witness. In a neurology malpractice case, the neurology expert witness would be expected to be experienced in issues such as ruptured aneurysms, seizures, spinal cord injury, head trauma, and strokes. Special qualifications may be required in emergency room physician cases. For example, in California the court can admit expert medical testimony only from a doctor who has had substantial professional experience within the previous five years as a physician and surgeon providing emergency medical coverage for a general acute care hospital emergency department.