In England, at the request of both parties, the medical and scientific witnesses may be excluded from the Court, but as a general rule they are allowed to be in Court, and hear the whole of the evidence of the case. In Scotland they are always excluded, although, by mutual consent, “experts” may remain to hear the general evidence on which they are to express their opinions, but when an expert is giving his opinion the others must leave the Court. In the latter country also, a medical witness who has been in Court cannot be examined on the facts of the case, but only on matters of opinion. A medical man is, however, sometimes allowed, on a special motion, to remain, although he is to be examined as to facts, and withdrawn when other witnesses are to be examined as to facts to which he is to speak. (See case of E. W. Pritchard, H.C. 1865; 5 Irv. 88.) In giving evidence the witness should--(1) Speak loudly and distinctly. (2) Answer questions categorically--Yes or no. (3) Never use superlatives. (4) Give answers irrespective of results of trial. (5) Express no opinion as to guilt of prisoner; state facts only. (6) Avoid using technical terms. (7) Avoid long discussions, especially theoretical arguments. When a quotation is made from a book by the examining counsel, the medical witness, before replying to a question based on it, should see that the quotation has been fairly and fully given, due regard being paid to the context. Neglect of this precaution may lead him into considerable difficulty. A medical witness should remember that he is not retained for a party, but in the cause of justice. He must, therefore, be candid in his manner and simple in his language. Mr. Haslam remarks that, however dexterous a witness may show himself in fencing with the advocate, he should be aware that his evidence ought to impress the judge, and be convincing to the jury. Their belief must be the test by which his scientific opinion is to be established. That which may be deemed by the medical evidence clear and unequivocal, may not impress the judge, nor carry conviction to the jury.