What is an Expert Witness?

In criminal trials, it is often necessary for either the defense or prosecution to employ an expert witness to explain complex concepts so the laypeople on the jury can understand them. For example, if a defendant is accused of fraud or insider trading, a financial expert witness may be brought in to explain what the charges mean, and how a person could commit the crime if so inclined. We’ll look at what is typically expected of an expert witness.

Objective Analysis

Ideally, an expert witness should be a respected professional in their field who uses their experience to objectively assess the charges they are asked to analyze. While they are always hired by one side or the other (the defense or the prosecution) they should provide a non-biased deposition, and then answer questions honestly in cross-examination.


A financial expert witness may be asked questions about banking or commodities regulations by both the defense counsel and the prosecutor. As with any other witness, they are sworn in to tell the truth, the whole truth, and nothing but the truth. Under penalty of perjury, the witness must answer questions honestly and to the best of their ability, whether their answers benefit the defense or prosecution. IT is possible that in cross-examination that an answer may be damaging to the side that hired the expert witness, but the purpose of the trial is to discover the truth.


The rates vary greatly depending on the means of the defendant and the specialized nature of the financial expert witness’ testimony, but expert witnesses are compensated for their time and the experience they bring to bear at trial. This sometimes calls into question the objectivity of the witness, but the tradeoff is their expert testimony, which is designed to lead the jury to the truth.