When no other defence to homicide is possible the claim of insanity is frequently interposed. Nothing is more confusing to the ordinary juryman than trying to determine the probative value of evidence touching unsoundness of mind, and the application thereto of the legal test of criminal responsibility. In point of fact, juries are hardly to be blamed for this, since the law itself is antiquated and the subject one abounding in difficulty. Unfortunately the opportunity for vague yet damaging testimony on the part of experts, the ease with which any desired opinion can be defended by a slight alteration in the hypothetical facts, and the practical impossibility of exposure, have been seized upon with avidity by a score or more of unscrupulous alienists who are prepared to sell their services to the highest bidder. These men are all the more dangerous because, clever students of mental disease and thorough masters of their subject as they are, they are able by adroit qualifications and skilful evasions to make half-truths seem as convincing as whole ones. They ask and receive large sums for their services, and their dishonest testimony must be met and refuted by the evidence of honest physicians, who, by virtue of their attainments, have a right to demand substantial fees. Even so, newspaper reports of the expense to the State of notorious trials are grossly exaggerated. The entire cost of the first Thaw trial to the County of New York was considerably less than twenty thousand dollars, and the second trial not more than half that amount. To the defence, however, it was a costly matter, as the recent schedules in bankruptcy of the defendant show. Therein it appears that one of his half-dozen counsel still claims as owing to him for his services on the first trial the modest sum of thirty-five thousand dollars! The cost of the whole defence was probably ten times that sum. Most of the money goes to the lawyers, and the experts take the remainder. It goes without saying that both prosecutor and attorney for the defence must be masters of the subject involved. A trial for poisoning means an exhaustive study not only of analytic chemistry, but of practical medicine on the part of all the lawyers in the case, while a plea of insanity requires that, for the time being, the district attorney shall become an alienist, familiar with every aspect of paranoia, _dementia præcox_, and all other forms of mania. He must also reduce his knowledge to concrete, workable form, and be able to defeat opposing experts on their own ground. But such knowledge comes only by prayer and fasting—or, perhaps, rather by months of hard and remorseless grind.