The ability to call upon an expert witness was first used in the 1782 hearing in which Civil Engineer, John Smeaton testified. Of course an expert cannot uncover every sordid detail of a murder or degree of insanity, but they can form an expert opinion from the evidence given them by the witness in question. The expert opinion is not intended to sway the jury one way or the other. It is simply more evidence to be taken into consideration by everyone involved.

During the course of any trial, an expert witness may be asked to testify on behalf of the plaintiff or defendant. Expert witnesses are often given the opportunity to examine or question the person in question so they may better assess the situation. After taking the time to examine them, the expert witness testifies under oath and delivers their expert opinion before judge and jury.

Expert Witness Testimony Can be Invaluable

Often in cases of injury, loss of earnings, costs of care and degree of insanity, an expert witness testimony is a very valuable source of information. An expert witness may be called upon by a lawyer or the judge presiding over the case. In the event of an insanity plea, an expert witness testimony is almost always relied upon. The expert will thoroughly examine the accused and make a decision based on their professional knowledge. They will then pass that information to the judge and jury by means of testimony in court. In addition to their expert opinion on the particular case, they may also give substantial evidence from the history of their profession.

On occasion, a prosecutor or defending attorney will request the help of an expert who gives false testimony or a "junk testimony" in order to try to sway the jury. If the expert's testimony is contested, the judge may appoint another expert in the same field to provide a conclusion. Sometimes the two experts agree. Other times, they offer differing opinions, casting doubt upon the use of expert witness testimonies.

Non-Testifying and Testifying Experts

Any party may hire experts to help them evaluate a case. A vehicle manufacturer may hire an expert mechanic to determine any potential failures in the vehicle's engine. If the expert so wishes, his or her identity will be withheld from the opposing party. This type of expert is considered a non-testifying expert. They simply help one party analyze issues that are important to the particular case.

A testifying expert is one that is present in court and testifies under oath. Criminal cases often use forensic scientists or psychologists. Other experts often called upon include engineers, accountants, consultants and professional caregivers. Testifying experts must be prepared to provide testimony as well as facts about the case and their opinion.

What Makes Someone an "Expert"?

A witness is considered an "expert" in their field if they've acquired the proper training, education, skill or experience. The expert witness needs to be unbiased when making their professional opinion known to the court. In the event of insanity pleas, psychiatrists, caregivers or other medical professionals are often questioned as expert witnesses.