Doctors are often asked to provide expert evidence for the courts. Whilst there is a considerable body of work in the legal literature, there is relatively little discussion and guidance in general medical literature. This is important as more doctors are drawn into the legal arena, and their ability to assist the court is a matter of consequence. The potential adverse effects in terms of the human, psychological and financial costs to the litigant parties, and the speed of access to justice, are considerable if the work is not done properly. Possible solutions to the present system are discussed and a set of guiding principles for acting as an expert witness is proposed.