OF all the causes which tend to discredit science, not one is more mischievous than the policy of the courts with regard to "expert testimony." Whenever a question of scientific fact or theory becomes involved in the settlement of a lawsuit, a swarm of "professional" witnesses are called, who testify on opposites sides, until neither judge nor jury can tell what is or is not really settled. Of these witnesses some are trained, some untrained; some are competent, some incompetent; some are scrupulous, others are unprincipled; and no sure rule of discrimination is properly applied between them. As a rule, all, though sworn, are expected to act like paid attorneys, each serving the side which employs him; and the one supreme test of capacity is that of shrewdness under cross-examination. Strange perversions of science thus get before the courts, to receive equal weight with worthy evidence; doubts are raised or exaggerated, and facts are misstated or suppressed. The highest scientific authorities, the men whose researches create science, are therefore averse to testifying, and rarely appear in the witness-box; for they can not risk their reputations upon one-sided or partisan statements, nor do they like the misrepresentations into which their evidence may be unscrupulously distorted. Under the present usage the expert bears witness for one side against the other; whereas the truth, being "neither black nor white, but gray," may stand in the middle of the disputed territory. The science of the court-room is litigious, not judicial; and no place is found for the unbiased presentation of fact, regardless of its bearing upon the personal interests at stake, and with fair credit given to genuine doubts and uncertainties. To the scientific partisan the court-room doors are wide open; to the scientific jurist they are practically closed, for no one wants his services. In criminal cases, perhaps, a better showing may be made; for here we have an impersonal state seeking to do exact justice, and its experts have no private ends to gratify. If, however, they are incompetent, the criminal, perhaps a poisoner, may escape punishment; and glaring cases of this kind are on record. Any experienced chemist can easily cite examples in point, for prosecuting attorneys are not always able to distinguish between true and false experts, and the latter sometimes destroy the evidence of crime in their blundering efforts to detect it.
Most men of science, and indeed most professional men, have two reputations—the one within, the other without the ranks of their colaborers. The two are rarely, if ever, quite commensur-