Courts often seek testimony and opinions about case facts from expert witnesses. These witnesses are distinguished from other types of court witnesses by virtue of their knowledge, expertise, and the opportunity to testify to opinions. Expert witness testimony is guided by legal rules and procedures. Rules regarding expert testimony focus on ensuring that expert testimony is relevant to the case, is based on valid and reliable methods, and will be helpful in aiding the trier of fact to understand evidence or determine facts. Experts can be hired by an attorney or by the court itself. When an attorney indicates that evidence will be presented by an expert witness, the opposing side has an opportunity to depose the witness in order to discover what the expert is going to say in court. The opposing attorney also has the opportunity to raise a challenge to the admissibility of the expert’s testimony. If the judge decides that the expert’s testimony does not meet legal admissibility criteria, the evidence will be excluded. Thus, it is important that experts prepare testimony that meets the requirements for legal admissibility. In addition to following legal admissibility rules, experts should follow a number of steps to provide adequate testimony. Thorough preparation is crucial. Experts should meet with the attorney to familiarise themselves with the questions that the attorney will ask and to rehearse questions that the opposing side is likely to raise. It is important that experts are transparent about the areas of strengths and weaknesses in the evidence they present. Overconfidence can lead to problems for admissibility of expert evidence and to negative perceptions of the expert testimony by triers of fact. The overall demeanour of an expert, such as knowledge, confidence, body language, and dynamic communication affects how triers of fact hear the evidence experts present, and ultimately how triers reach decisions in the case.