If we rid ourselves of the assumption that we can measure the moral culpability of the accused, the whole process of a criminal trial consists in the assemblage of facts, the discussion, and the decision upon the evidence. For the classical school, on the other hand, such a trial has been regarded as a succession of guarantees for the individual against society, and, by a sort of reaction against the methods of legal proof, has been made to turn upon the private conviction, not to say the intuition, of the judge and counsel. A criminal trial ought to retrace the path of the crime itself, passing backward from the criminal action (a violation of the law), in order to discover the criminal, and, in the psychological domain, to establish the determining motives and the anthropological type. Hence arises the necessity for the positive school of reconsidering the testimony in a criminal case, so as to give it its full importance, and to reinforce it with the data and inferences not only of ordinary psychology, as the classical school has always done (Pagano for instance, and Bentham, Mitter<p 166>maier, Ellero, and others), but also, and above all, with the data and inferences of criminal anthropology and psychology. In the evolution of the theory of evidence we may distinguish four characteristic stages, as M. Tarde observed--the religious stage, with its ordeals and combats; the legal stage, accompanied by torture; the political stage, with private conviction and the jury; and the scientific stage, with expert knowledge of experimental results, systematically collected and studied, which is the new task of positive procedure. We must glance at each of the three elements of the criminal trial: collection of evidence (police and preliminary inquiry); discussion of evidence (prosecution and defence), and decision upon evidence (judges and juries). It is evident in the first place, as I remarked in the first edition of this work, and as Righini, Garofalo, Lombroso, Alongi, and Rossi have confirmed, that a study of the anthropological factors of crime provides the guardians and administrators of the law with new and more certain methods in the detection of the guilty. Tattooing, anthropometry, physiognomy, physical and mental conditions, records of sensibility, reflex activity, vaso- motor reactions, the range of sight, the data of criminal statistics, facilitate and complete the amassing of evidence, personal identification, and hints as to the capacity to commit any particular crime; and they will frequently suffice to give police agents and examining magistrates a scientific guidance in their inquiries, which now depend entirely on their individual acuteness and mental sagacity. <p 167>