In a court of law, facts are not considered facts unless they are proven, or in some cases disproven by irrefutable evidence. An expert witness may be called for this purpose. As such an expert witnesses testimony must be balanced and unbiased to ensure a just outcome.
Often it is the evidence of an expert witness that is the tipping point in a case with a sound, well-informed and regarded judgement. It is not enough to be an expert in your chosen field, an expert witness must have report writing and courtroom skills to be able to clearly and concisely present their opinion evidence and must also understand what that particular court requires and expects from them as an expert witness and the correct format for writing their report in compliance with strict legal guidelines.
These skills are developed over time and can be enhanced with training, available from various sources and providers. When the intention is not to place an expert's opinion before the court, the expert's role is as an expert advisor, who can take on various tasks behind-the-scenes. In summation, an expert witness is also an expert with specialist knowledge beyond that of a lay person whose knowledge supports their carefully regarded opinions which may be placed before a court or other judicial body. Essentially, the expert witness's role is to provide specialised analysis and opinion to assist the court in reaching a decision. This opinion is based solely on evidence of fact.
It however, is much more complex than these broad terms and changes by definition and admissibility by jurisdiction, practice note, state, and courts. A person, with specialised experience, when called upon to act as expert witness, must conduct him/herself in accordance with the specific roles and duties of the Expert Witness' as designated by the Code of Practice and that of the Courts. It is the instructor's responsibility to give the expert the rules in relation to the requirement for their report. The role of the expert witness in litigation is to bring assistance to the court and assist in the administration of justice in the provision of an opinion or facts that is based on the expert's competence. Such information is based on subject matter which falls outside the knowledge, experience and skill of most people in the same industry. It is usually formed over many years from both practical and life experience over academic experience.
The court needs to be satisfied that the expert has the knowledge relevant to the question before the court and is competent to talk objectively and independently. One must understand that an opinion is only useful if it is derived from one of the expert's core competence areas, which includes the relevant matters before the court. So it must be the main duty of an expert to be accountable to the court in their role as an independent expert. The expert is subject to what any witness would be subject to in a court. They must be sworn in and respect the court and duty to give evidence of fact in to their knowledge to be the truth, the whole truth and nothing but the truth. In addition to this, the expert is charged with another obligation to the body of knowledge and understanding from which his or her expertise is expected to be drawn upon.
They must recognise their own limitations and inform the court of possible issues with their findings, or any better and further particulars that would be required to qualify a finding. In litigation, it is serious - and likely that a person could be detrimental by the evidence given so the lay expert must at all times take caution not to cross into any area of 'guessing'. They must disclose areas which they are unqualified to give any opinion or evidence on and to what extent. Throughout the life as an expert witness it will also often be a requirement to work with other experts in a respectful manner.
This helps validate the evidence and gives the court further assurance of the consistency of the evidence. So, it is utmost important for the expert to realise their secondary duty as the body of knowledge and understanding of the primary purpose. There is also a third duty the expert owes, and this is to the party whom sought their engagement. Although the expert is briefed by this person, they still have the primary duty to the court. To the client (as the case may be) their duty is to give advice in the context of both duties described above and this strengthens the fact that the expert is independent and should not advocate for a client.