The purpose of appointing an expert witness is to tap on the expert’s specialised knowledge and skills to aid the Court in understanding specific topics of interest in a case. Unlike the lay witness who gives evidence of fact based on what he has personally seen or heard, an expert witness is in the unique and privileged position to express expert opinions in his area of specialisation.
The forensic scientist must be prepared to provide expert testimony from the onset of being retained or engaged for a case. He must be cognisant of his duty to the Court, be aware of the contending issues in the case-at-hand and present his testimony professionally, in an orderly and convincing manner. The expert witness should not take umbrage when challenged in court by an opposing legal practitioner or expert, but regard probing questions during cross-examination as the legal practitioner’s means to seek the truth. As Albert Osborn so aptly expressed, “A mere opinion anyone can give, but an opinion based on accurate and intimate knowledge, if logically presented and adequately illustrated, will not only bear the fierce light that beats upon the witness-box but will be clarified and strengthened the more it is attacked.”
Pre-trial conferencing with the legal practitioner is essential for an effective court testimony. It will be helpful for the expert witness to understand how legal practitioners think and reason to better communicate with them before the trial and in the courtroom. The understanding and rapport between the legal practitioner and the expert witness may become the deciding factor between a powerful testimony versus a weak one. The legal practitioner must be familiar with the key findings in the expert report, the basis and strength of the conclusions, and limitations of the evidence. Both the legal practitioner and the expert witness have to recognise that the discovery of scientific facts alone is inadequate; they have to assist the Court to see the facts and hypotheses presented in the testimony.
Each opportunity on the stand strengthens the expert, and provides an invaluable learning experience for him. Providing effective expert testimony and the mastery of this skill is a long-term process that requires constant practice and review, often aided through feedback and court evaluation from senior scientists, peers and legal practitioners. The expert witness should constantly strive to improve himself by being open minded, exercising critical thinking, and honing the skills required to achieve mastery in his areas of expertise.
To wit, the expert witness must be mindful that he owes an overriding duty to the Court to be honest, objective and impartial, presenting his testimony in a clear and convincing manner, and substantiating his opinions with scientific findings. Even the slightest mistake on the part of the expert witness may be too much to bear as report findings and expert opinions carry enormous weight, and have far-reaching implications not only to persons directly involved in the incident, but their immediate families, the general public and judicial system. Honesty requires the expert to truthfully acknowledge and not downplay or trivialise any mistake – large or small – in the forensic report and oral testimony. Defending an error only diminishes the expert’s credibility.