Cases that involve personal injury that is either physical or psychological in nature require the testimony of an expert witness. In civil cases, the plaintiff and defense acquire the testimony of an expert witness. Expert witnesses are normally enlisted to testify in such cases as medical malpractice, vehicle accidents, slip and fall incidents, and much more. Expert witnesses are either provided by the state such as in a criminal trial, or retained by a party in a civil trial. The expert witness is one of the most important witnesses in a trial.

A retained expert witness is an expert who has been retained by a law firm to testify on the firm's behalf. This is a witness who has the specific education, training, skills, and experience in a particular area to form an expert analysis and opinion that is presented at trial. These witnesses are usually paid on an hourly basis for their expert analysis and research, as well as for their testimony at trial. They are paid a fee regardless of the outcome of the case. Fees can range from $50.00/hour to $500.00/hour. They only provide testimony regarding the facts of the case and how they arrived at their opinion. Like non paid experts, they have to be certified by the court to be considered an expert. They must have the experience and education that is relevant to the particular issues of the case. The testimony should be candid, objective, and truthful. Most work in the field that they are giving testimony about and they must be able to defend their opinions against tough cross-examination by a prosecutor or attorney.

Although they are paid by a law firm, retained expert witnesses have to adhere to a proper code of conduct and ethics. They must be unbiased and analyze information objectively. They must also have the ability to interpret reports and other applicable information in order to make an informed opinion. Their testimony offers opinion evidence rather than fact evidence. Just like any other expert witness, they must have a solid reputation within their field of expertise. An expert witness with a shady reputation will not help a case. The court is more receptive to a witness who is respected by their professional community. Jurors and judges will be more likely to accept the testimony of a qualified and respected witness. Retained expert witnesses can include: medical specialists, engineers, law enforcement specialists, scientists…etc. A positive verdict is more likely to occur if one uses the testimony of an experienced and respected witness. The expert may also be required to give testimony regarding the severity of damages when the court is considering the amount that will be awarded.

A retained expert works for the attorney that is on the case. Attorneys are accountable under strict ethics and state professional codes. The retained expert must abide by these ethical codes when working with an attorney. The attorney should explain the ethical guidelines to the expert. The expert has a duty not to disclose any confidential client information..Other ethical guidelines they must follow when working with a law firm include: avoiding conflicts of interest, protecting the client's reputation, and avoiding appearance of impropriety when representing the client. An expert who fails to uphold standard ethical guideline can not only negatively affect a case, but could be found liable for failing to uphold the guidelines.

A retained expert witness plays a key role in most civil and criminal cases. Most prosecutors and law firms have a list of experts. An attorney will be able to determine what expert meets the needs of the particular case. An expert witness can make or break a court case.