Legal testimony can be provided by an individual who is considered to be an expert in his specific occupational field. This individual must typically provide credentials as to their education and professional background prior to providing information on the witness stand. The facts revealed during this type of testimony are considered outside the realm of common knowledge, and require additional training and skills beyond those of what may be considered a standard education to understand and interpret.
An expert witness is often called during a civil or criminal court trial to evaluate evidence from an academic perspective. This individual may be called upon by either the defense or the prosecuting attorney. The legal counsel typically exposes the witness to any relevant evidence at hand, such as photographs, audio or visual recordings, medical records, or x-rays, among other items. The witness then provides legal testimony by assessing the evidence based on his extensive professional experience, under oath, in a way that the judge and jury may consider fact.
Some expert witnesses create a career from providing legal testimony. These witnesses tend to focus on one area of expertise, and maintain current, qualifying credentials in that field. For example, a chiropractic doctor can be treated as an expert in the area of back injuries. He may be called upon by various prosecutors to testify regularly in auto accident cases on the severity of any back injuries a plaintiff received. The expert typically attempts to demonstrate a unique ability to communicate well with a jury in layman's terms, and hopes to provide crucial information that can play a large role in determining the outcome of a court decision. Successful expert witnesses often create a network of lawyers with whom they work on a consistent basis.
The legal testimony provided is generally limited to factual information, and should not include the opinion of the witness. Though the expert may be able to draw logical conclusions from the evidence provided based on his extensive research and education, those conclusions must be treated as that individual's opinion. Such testimony is then referred to as expert opinion. In the example of the chiropractor, the doctor may testify as to the factual type of injury a plaintiff received. He may include his opinion on the regimen of treatment and medication the plaintiff requires to facilitate healing, however he cannot assign blame to the defendant in the case for causing the injury.
