has. He should, however, not hesitate to inform his client as to the hopelessness or injustice of his case and should stand ready to withdraw if that appears to have become his duty.

An engineer sometimes declines to go upon the stand because crossexamination is likely to bring out some weakness in his client's case, and yet he may feel free to advise the lawyer in court in order to establish a serious weakness in the opponent's case. A man with high standards will act or refuse to act as seems to him right. A man with low standards will not be guided by anything written here.

Opinions. With relation to his work as an expert witness it has been stated in a previous chapter that, in general, witnesses may not state opinions except in the case of experts. Engineers often serve as experts and thus may express opinions. Expert opinion is allowable when the subject matter has the nature of a science or trade, which requires study or experience, or both, to understand it, so that persons inexperienced in the art or science who constitute the jury are likely to be left in doubt after all the facts are proved, unless aided by expert opinion. Whether such expert opinion may be introduced rests with the judge. The jury may or may not be convinced by it, but will give to it such weight as they see fit and decide upon questions of fact accordingly.

Qualifying. The expert must "qualify." He must state the skill, knowledge, or experience he possesses, which as a rule he has gained in his trade, profession, or calling. In some cases he is qualified by study or scientific research rather than by direct experience. Teachers of natural sciences have often been experts by virtue of their study.

Who are Experts. Locomotive engineers may be experts on many matters in the running of trains, as may also railroad conductors, brakemen, and others upon points with which they are familiar. Civil engineers or mechanical engineers who have made themselves familiar with the theory of brake resistances and know what practical results have been reached, are competent to testify as to the distance in which a given train could be stopped. This, however, is not strictly opinion evidence, certainly if the distance is stated within limits and not exactly.

Cross-Examination on Qualifications. Cross-examination of the expert as to qualifications is to be expected, and a favorite scheme is to ask the witness if he is expert upon some very narrow line of the field. A witness who well understood all about chains was asked if he was an expert on "foundry chains," a chain in a foundry being in question. Not having given especial attention to any chain used in a foundry, and having a fine conscience, he said "no" and was promptly excused. He should have stated that he thoroughly understood chains and foundry chains were chains, and could then, if pushed, answer "yes." The

engineer should consider carefully what he will state as his qualifications, and weigh carefully his answers in cross-examination as to these.

Court Decides on Qualifications. The court is the sole judge of the qualifications of a witness as an expert, that is as to whether he shall be allowed to testify as an expert. The jury, however, is the sole judge as to the weight or credit to be given to his testimony as to opinions, or as to scientific facts or principles propounded by an expert.

Opinions in Disfavor. Opinion evidence is in considerable disfavor. It seems possible, in many important cases, to obtain the opinions of experts in support of either side, and often diametrically opposed to each other. Medical men and handwriting experts often disagree, as do also engineers.

Scientific Facts or Principles. The evidence of engineering experts, to a large extent, is not "opinion" evidence. Quite largely the evidence is a statement of scientific facts or principles which apply to the case in hand. The function of the engineer, more often than not, is to discover and correlate the scientific principles and facts which apply, and to arrange them in such simple and clear form as to convince the jury. None but an expert could so present them and establish their bearing.

Measure of Value of Evidence. An attorney stated to a witness in his first expert case that "the value of your evidence will depend upon its soundness and the reasons you present to support it." The evidence was as to values to various parties of an improvement determined upon. These were established from statistical data, and by logical deductions from them. From these the commissioners who heard the case were able to draw conclusions without attaching much, if any, importance to the quality of the witness as an expert. The facts presented were what counted. Except by an expert, these facts would not have been presented.

Expert but not Opinion. A statement by a surveyor or engineer as to the amount of land which would be flowed at a given height of water may be expert, but certainly is not opinion evidence if the proper measurements and computations have been made. The statement is one of a scientific fact.

A competent civil or a mechanical engineer may express an opinion. of the cause of an accident, but his testimony is far more convincing if he recites facts within his knowledge which lead him to the opinion he expresses. If the facts lead the jury to the same result, his opinion is a negligible part of the case.

Subordinate Opinions. So far as possible the engineer should arrange his evidence in such form that his personal opinion is not the deciding element. His judgment or opinion may determine what scientific facts or theories are to be applied in any case in hand, but any initiative of such

sort may still leave the jury to accept the theory on its merits rather than as the engineer's opinion purely.

Values. Statements as to values, or as to the probable effect of certain constructions, may be purely opinions. They may often be the logical result of scientific facts recited by the experts. Values of public utilities are often fixed by earnings or costs, or both combined, and a jury, with the facts suitably presented, often becomes capable of forming a correct judgment from these facts.

Attitude as Witness. When upon the witness stand, the answers of the expert witness should appear to be clear, frank, fair, and free from bias. They should also be so framed, if possible, that the inexpert jury may understand them. There may be cases where a juror's respect for expert testimony will be in proportion to his inability to understand such superior wisdom, but it will not do to count on this with twelve hardheaded men. Before a commission, clearness is equally desirable. Cross-Examination. Under cross-examination, ordinary witnesses are sometimes asked if they had a "rehearsal " with their attorney. Such a question would rarely be asked of an expert, and a statement that a consultation was necessarily had would not prejudice the case. A witness under cross-examination should keep cool, consider well his answers, should not be driven into a show of anger, should not attempt to be smart," and should avoid the appearance of bias even under crossexamination.

Yes or No. An answer "yes" or no may be demanded and in most cases must be given. Where either answer would convey the wrong impression, the witness may sometimes ask the protection of the court against answering either way. He may sometimes answer "yes and no " if this is appropriate and let the opposing lawyer ask an explanation if he wants to do so. An illustration of a question to which an answer "yes" or "no" is misleading is: "Have you quit your habit of beating your wife?"

Testing Expert's Knowledge. The cross-examination may seek to discredit the expert, and general questions not directly applicable to the case may properly be asked to determine his qualifications. Questions requiring computations need not be answered off-hand,, but a willingness to compute and testify later may be appropriate. It happens, in rare cases, that an engineer states the results of a computation and later discovers an error; a return to the stand to correct the error is the proper course, and probably will not injuriously affect other testimony given.

Refreshing Memory. Where extensive computations have been made, the witness may have memoranda with him and use them "to refresh his memory." It is a necessity in this case. An engineer may always use memoranda to refresh his memory. He may testify that he remembers

the memoranda to be correct, or it will serve if he remembers that the memoranda were correct when made.

Maps and Photographs. He may introduce maps or photographs as evidence if he can state that they are correct. He may, however, use them to illustrate his testimony without establishing their accuracy. In the first case, as evidence the maps or photographs are commonly made exhibits, but in the latter case they are not.

Books of Science. The engineer may not read books of science as evidence. He may, perhaps, be allowed to cite the opinions or statements of writers of books, but these must have become his own opinions, or else his conclusions or statements of scientific facts, in order to be admissible in evidence.

In cross-examination, books of science may be used to test the expert's knowledge of the subject, in an effort to discredit him, and a witness not well grounded may appear to disadvantage in such case.

Opinion on Testimony in Case. The expert witness often sits through the trial and hears all the testimony given and is then asked his opinion, perhaps as to the cause of an accident testified to. If there is no conflicting testimony he may give his opinion. If there is any conflicting testimony, he cannot give an answer which depends upon his accepting or rejecting any part of such conflicting testimony. The jury only is permitted to pass upon the credibility of witnesses and the truth of testimony presented. If the expert has made an investigation he may have based his opinion upon that, and his opinion may not have changed as the result of any testimony he had listened to, but he can go no farther than this; he cannot discriminate between testimony offered by others.

Advice to Experts. The following advice as to expert testimony was many years ago made to the American Society of Civil Engineers by a distinguished engineer and expert, parts of which have been referred to elsewhere in this chapter:

"That the court always understands that an engineer has been previously advised in regard to questions upon which his direct examination will be made, and that he has prepared himself by study and reasoning to apply to the case in hand all of the scientific principles which are necessary to elucidate it.

"It is, therefore, unwise to attempt to conceal from the court that the engineer has been in consultation with the lawyers upon the side upon which he has been called, or that he has been paid or is to be paid professional prices for his services. "No provocation on the part of a lawyer will justify an uncourteous reply, and it is unwise to give back a sharp or witty answer.

"If the lawyer uses improper language in addressing the witness, the latter may appeal to the judge.

"If questions requiring study and research are put to the witness, he may reply, 'I have not considered the subject under that aspect sufficiently to reply,'

or 'I shall require a little consideration before I can reply; I will make a note of your question, and answer it as soon as possible.'

"A witness is often called upon to express an opinion on some subject which is a matter of exact or approximate measurement and calculation; it is often impossible for him to make such calculations accurately in the presence of a roomful of people. His proper course, under such circumstances, is to make a note of the question and inform the counsel that he will make the calculation and give it in writing. In strict law, however, a witness on the stand is not compelled to make any calculations except those of a simple and elementary character."

Services before Trial. Before the trial, the expert engineer can render valuable assistance in defining and formulating the technical issues involved, in indicating the documentary evidence and the physical facts necessary to the successful conduct of the case, as well as in securing the witnesses to establish important facts or scientific principles. This will be done in consultation with the lawyer. The engineer usually has acquired a more thorough habit of investigation than is common with lawyers. Most lawyers are inexpert in matters of engineering science, and the engineer's services may be of great value in the preparation of a case. He should anticipate so far as possible the expert testimony on the other side and prepare to meet it. The lawyer must usually be advised as to what questions to ask, and witnesses should know the scope of the evidence they are expected to establish.

The advising expert, in anticipating cross-examination, should not allow himself or others to go on the witness stand if the probable effect of cross-examination will be to bring out facts prejudicial to his client to an extent sufficient to more than offset the favorable evidence established by the direct examination. Sometimes more favorable results may be extracted by the cross-examination of an honest expert on the opposing side than can be expected from one's own witness. The expert engineer adviser ordinarily must shape the questions for such cross-examination.

To Know Facts. Engineers or surveyors testifying to measurements should know them to be correct, and should read the tape or the transit if necessary to do so, and also test the tape where precise measurements are involved. Measurements read from drawings may be attacked as hearsay, while field measurements of lands or actual measurements of structural parts will be competent evidence.

Compensation. The question sometimes arises as to what compensation an expert witness is entitled to, and involved with it whether one may be summoned as are other witnesses when expert testimony is expected of him. It has been held in some jurisdictions that a public duty exists for everyone to contribute his share in securing justice for others and the expert must do his duty in this way at an ordinary witness' pay. This