Purpose

• Expert testimony is not used in every case because only certain cases require expert opinion. The purpose of expert testimony is to provide the judge or jury with expertise on a technical issue. An expert provides her opinion about a particular topic in court or in a deposition. In some cases, the party using expert testimony must provide the court with the substance of the testimony prior to the commencement of the proceeding.
  
  

Rule

• Federal and state law regulates the use of expert testimony. Under Federal Rule of Evidence 702, a person is qualified to give expert testimony in the form of an opinion if the person has scientific, technical or other specialized knowledge that will help the trier of fact. It is up to the judge to determine whether the expert testimony is reliable. The trier of fact can use the expert testimony to help decide issues in the case or can disregard it.
  
  

Types

• Anyone with expertise can give expert testimony. A qualified expert must have credentials, such educational qualifications and experience in a particular field. The expert may use methodology to support his opinion. The trier of fact can consider whether the methodology used by the expert is peer reviewed. An expert is normally a practicing professional or a professor. The most commonly used experts include architects, doctors, economists, engineers and accountants.
  
  

Medical Malpractice

• Expert testimony is commonly used in medical malpractice cases. Expert testimony assists the trier of fact in understanding the technical information. An expert can help the judge or jury to determine whether the doctor failed to follow the standard of care used by other doctors and whether the doctor's breach caused injury to the plaintiff.
  
  The expert will testify about how a competent doctor would have acted in the same situation and whether the doctor acted as a competent doctor. The expert will also testify about whether the doctor's incompetence was the cause of the plaintiff's injury. It is not necessary to use expert testimony when the facts, such as when a doctor has sole control over the object that causes the injury, make it clear or obvious that the doctor is at fault.