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In a judicial court system, an expert witness is usually one that has expertise or knowledge about a particular discipline or field that goes well beyond what would be expected of a lay individual. When that expertise and knowledge is available to the court, the person is considered an expert witness. In all, they are used to assist the jury or the judge in understanding the basic issues involved in the case in an effort to reach a just and sound decision.

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Dispensing Expert Evidence

The most basic fundamental characteristic involved in expert evidence is actually opinion. Typically, a lay witness (not an expert) is only allowed to provide one type of evidence, namely only the facts in the case. They do not have the ability on the stand to offer an opinion to the jury or judge. Alternatively, though, it is the task or duty of the expert witness, which might be an accident investigator, a medical doctor, a forensic expert or other professional that can assist the court and the jury in reaching a decision based on their opinion. It might also be technical analysis that they offer or infer that is different from actual factual evidence.


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Why an Expert Witness Is Needed

While there is a myriad of reasons that an expert would need to expound their opinions in a court of law, usually it is to detail technical or scientific knowledge. However, the opinions they disseminate to the jury must be deemed admissible by the judge before they are ever presented in a court of law. This is based on admissibility.

For opinions to be admissible, the expert witness will need to have sufficient experience and meet the qualifications necessary for the evidence they provide. This is often determined by the judge in the case. Courts often exercise the power to exclude the testimony of expert evidence for numerous reasons. The court always reserves the right through its power to reject evidence that could be otherwise admissible.

An Expert Witness’s Duties

Like any other witness taking the stand, it is an expert witness’s duties to be truthful in regards to the facts of the case. In addition, they must be honest as to their opinion. This applies to both oral evidence and written reports, whether or not they had taken an oath previously to generate their reports.

In addition, the American Bar Association indicates that there are ethical considerations involved in being an expert witness1. They cannot simply ignore information that could pose to be damaging to their client’s side of the case if it were to come to light. They have an ethical responsibility to avoid suppressing any opinion that might be damaging or tantamount to lying or committing perjury as to bolster or undermine the case of the defendant or client.

Not all expert witnesses will make it to the stand. They may be hired for a variety of other reasons that could include:

  • Preparing evidence
  • Advising client’s attorneys or the client
  • Proposing remedial works
  • Forming opinions
  • Investigating facts

However, when on the stand at a trial in a court case, the expert witness needs to provide independent assistance by way of an unbiased objective opinion that directly correlates to the matters of which he or she has expertise. The expert witness should clearly state each pertinent fact and every assumption upon which all of their opinions have been based. They should never omit to consider offering any material fact that could in some way detract from his or her concluded opinion.

It is important that the expert witness make clear any time a particular issue or question asked falls outside the scope of their expertise. In fact, if any question that has not been properly researched is asked of the expert, it should be there testimony that they have insufficient data available to provide an opinion at that time.

Whether offering an opinion on the stand, or previously writing it down in a report, the expert needs to assure that every bit of information contains the entire truth and nothing but it. Any qualifications used to formulate the opinion must be contained in the report. This includes any initial meetings with the attorneys when evidence was obtained for the trial. Under no circumstances should the expert witness ever assume a role of being an advocate in the case.

The court deems an expert evidence to be an independent product that has been developed by the expert without being influenced by the content or form of any exigencies (urgent demand) of the litigation.

The most successful and respected expert witnesses are those that are always prepared to reconsider their opinion whenever appropriate. This is often a result of receiving new information or whenever considering another expert’s opinion.


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