An expert witness is a person with specialized skill sets whose opinion may help a jury make sense of the factual evidence of a case testimonies from expert witnesses can have a tremendous influence on the final decision of the judge as such the admissibility. Expert witnesses are now an accepted part of criminal and civil trials the use of expert witnesses and the admissibility of their science has developed over the last 250 years when the concept of allowing an expert witness to give opinion evidence on the facts of other witnesses was allowed by lord mansfield in the case of folkes vchadd in 1782 this paper briefly describes how court . The global nature of crime often requires expert witnesses to work and present their conclusions in courts outside their home jurisdiction with the corresponding need for them to have an understanding of the different structures and systems operating in other jurisdictions this book will be a resource for uk professionals as well as those from overseas testifying internationally as to the . An expert witness likeany other witness may testify as to the veracity of facts of which he has first hand experience but this is not the main purpose of his or her testimony an expert is there to give an opinion and the opinion more often than not will be based on second hand evidence as stated by mr justice dickson in the above passage an expert may and in fact preferably should