In the aftermath of the Roy Meadows affair a book which explains the role and responsibility of the expert witness is very timely. Paul Ellner, Emeritus Professor of Microbiology and Pathology at Columbia University, purports to provide the critical tools needed for the microbiologist to make an effective courtroom appearance. It contains some sound advice, much of which is common sense, but worth emphasizing; for example, 'If you take a break to use the rest room or eat lunch, do not discuss the case'. There are some entertaining case studies, but it is the legal language and procedures which will be of most interest to scientists who are starting out as expert witnesses. Obviously, the author relates this to his own experience in US courts; UK procedures are very different and I doubt, therefore, that there will be much demand for this book by SGM members.