The popular media is rife with examples of scientists delivering the telling evidence in a police investigation or court case. Often the computer will show a positive match or the investigator states that the physical evidence does not lie, usually with the suspect immediately confessing the wrong doing. The reality, however, is that science is replete with errors, mistakes and misinterpretations. Courts must deal with these limitations while trying to deliver justice to all involved. Jurors, expecting to have one person who can stroll in and tell them exactly what happened, generally have to deal with multiple experts testifying to the horrible mistakes made by the other side. This book presents seven examples to illustrate the legal and court procedures in which one of the authors, a chemist, acted as an expert witness. The examples of the cases chosen include drunk driving, house fires, poison products, floods, and slip and fall. The cases are presented in a both legal and scientific manner intended to provide professionals (lawyers and judges), as well as the general public, insight into the practical application of science in real court cases. Included are the original scientific reports and, where possible, the judgements of the courts interpreting the data. Examples of both Canadian and American cases are used. The introductory chapter of the book and the final two chapters deal with the role of the expert witness and the laws that determine their evidence and its consideration by the court.