The role of the expert witness and the opinion evidence that they present in court has caused, and continues to cause, issues; experts often do not agree and may hold widely differing opinions or may present their evidence in ways which make it difficult for a jury to follow. More recently, the increase in the use of DNA evidence to examine past cases has shown that experts can be the cause of miscarriages of justice. It quickly becomes apparent that the issues around the use of expert witnesses are global, but each criminal justice system has differences that anyone attending court in this role needs to understand prior to giving evidence. Despite this, the literature which exists around the role of the expert is surprisingly limited in scope.