If unable to decide as to the cause of death without a _post-mortem_ examination, tell the jury so at once; the most experienced pathologist will do so the most often. Thus you may tell them, by way of apology, that any organ of the body may be ruptured without external signs of injury being apparent. Distinguish =what you have been told= from what you have found by personal examination. A knowledge of the facts differs from a knowledge of the records of those facts. State what you =knew professionally= as to the health and the habits of the deceased, but do not condescend to detail; it is sufficient to say, “I treated him,” or “I prescribed;” you need not specify =how= unless required so to do. Don’t offer any explanations unless directly asked; decline to give “expert opinion” testimony unless you feel fully competent so to do. The jury value evidence by the exactness of statement of, and the powers of observation evidenced by, a witness. Little benefit is gained by cross-examining one who is obviously telling the plain truth. Don’t exaggerate or estimate—“blessed are the pure in fact” in a law court; in measurements and descriptions be accurate, quoting figures where possible. You must answer =all questions= put to you, excepting such as would tend to incriminate yourself; before you answer such questions, the Coroner must warn you of the possible legal consequences if you answer. There are no medical secrets which may be kept between a patient and his medical adviser when they are probed in a court of law: if, however, you strongly object to answer, appeal to the President of the Court, or answer in writing. Think twice before adversely criticizing the actions of another medical man; remember, =symptoms and signs may alter= from day to day. You may not quote text-books of living authors, but you may say what authors support your view. If a text-book is quoted for or against you, =strictly verify= the text, the context, and the date of publication, before affirming or denying the quotation. After giving evidence, hand in the labelled and numbered =exhibits= which have been handed to you by the police or found by yourself. “Real evidence” is, however, capable of fallacious handling, e.g., “Here’s the note! I made it at the time!”—but _did_ you? It may be wise to take an “anatomical” skull into court for illustration. The body of the Coroner’s officer is always available for ocular =demonstrations= to the jury of the sites of injuries, etc. If any important point has been omitted by the questions (e.g., of a non-medical Coroner), volunteer the undisclosed information which you possess. In conclusion, state the probable =cause of death=, especially assuring the jury if it was, in your opinion, natural; and if it could have been retarded by efficient medical advice. Beware of being didactic on non-medical matters; such action is a fruitful source of the “differences of doctors.”