with it. In short, wherever the subject of the testimony consists in classifying or identifying or testing or authenticating, the witness's observation necessarily involves two elements, (1) an observation of the class, type, or standard, and (2) an observation of the thing to be classified or identified. Both elements must be supplied in his testimony.

It may be noted that here it is not uncommon to supply the second element by hypothetical presentation. Thus, in valuing the cost of a house's construction, the witness may have actual observation of only the value standards of different sorts of houses, and then the features of the particular house to be valued may be placed before him by hypothetical description. So a witness to the identity of a murdered person with one J. S. may have had actual observation of J. S. but not of the body of the murdered man, and the latter element may be supplied by showing him a photograph assumed to be that of the deceased, and then verifying the photograph as that of the deceased.

235. HANS GROSS. Criminal Psychology. (transl. Kallen. 1911. § 35, p. 187.) I. Sense Perceptions. Our conclusions depend upon perceptions made by ourselves and others. And if the perceptions are good, our judgments may be good; if they are bad, our judgments must be bad. Hence, to study the forms of sense perception is to study the fundamental conditions of the administration of law, and the greater the attention thereto, the more certain is the administration.

1. The Senses. (a) General Considerations. The criminalist studies the physiological psychology of the senses and their functions, in order to ascertain their nature, their influence upon images and concepts, their trustworthiness, their reliability and its conditions, and the relation of perception to the object. The question applies equally to the judge, the jury, the witness, and the accused. Once the essence of the function and relation of sense perception is understood, its application in individual cases becomes easy.

There has always, of course, been a quarrel as to the objectivity and reliability of sense perception. That the senses do not lie, "not because they are always correct, but because they do not judge," is a frequently quoted sentence of Kant's. .. Descartes, Locke, and Leibnitz have suggested that no image may be called, as mere change of feeling, true or false. Sensationalism in the work of Gassendi, Condillac, and Helvetius undertook for this reason the defense of the senses against the reproach of deceit, and as a rule did it by invoking the infallibility of the sense of touch against the reproach of the contradictions in the other senses.

That these various theories can be adjusted is doubtful, even if, from a more conservative point of view, the subject may be treated quantitatively. · The modern quantification of psychology was begun by Herbart, who developed a mathematical system of psychology by introducing certain completely unempirical postulates concerning the nature of representation and by applying certain simple premises in all deductions concerning numerical extent. Then came Fechner, who assumed the summation of stimuli. And finally these views were determined and fixed by the much-discussed Weber's Law, according to which the intensity of the stimulus must increase in the proportion that the intensity of the sensation is to increase;

i.e. if a stimulus of 20 units requires the addition of 3 before it can be perceived, a stimulus of 60 units would require the addition of 9. This law, which is of immense importance to criminalists who are discussing the sense perceptions of witnesses, has been thoroughly and conclusively dealt with by A. Meinong.

Modern psychology takes qualities perceived externally to be in themselves subjective but capable of receiving objectivity through our relation to the outer world. . . . The qualitative character of our sensory content produced by external stimuli depends primarily on the organization of our senses. This is the fundamental law of perception, of modern psychology, variously expressed, but axiomatic in all physiological psychology. We see things in the external world through the medium of light which they direct upon our eyes. The light strikes the retina, and causes a sensation. The sensation brought to the brain by means of the optic nerve becomes the condition of the representation in consciousness of certain objects distributed in space. . . . We make use of the sensation which the light stimulates in the mechanism of the optic nerve to construct representations concerning the existence, form, and condition of external objects. Hence we call images perceptions of sight. . . . Our sensations are effects caused in our organs, externally, and the manifestation of such an effect depends essentially upon the nature of the apparatus which has been stimulated.

There are certain really known inferences, e.g. those made by the astronomer from the perspective pictures of the stars to their positions in space. These inferences are founded upon well-studied knowledge of the principles of optics. Such knowledge of optics is lacking in the ordinary function of seeing; nevertheless it is permissible to conceive the psychical function of ordinary perception as unconscious inferences, inasmuch as this name will completely distinguish them from the commonly so-called conscious inferences. The last-named condition is of especial importance to us. We need investigation to determine the laws of the influence of optical and acoustical knowledge upon perception. That these laws are influential may be verified easily. . . . If we were unaware that light is otherwise refracted in water than in air, we could say that a stick in the water has been bent obtusely, but inasmuch as everybody knows this fact of the relation of light to water, he will declare that the stick appears bent but really is straight.

From these simplest of sense perceptions to the most complicated, known only to half a dozen foremost physicists, there is an infinite series of laws controlling each stage of perception, and for each stage there is a group of men who know just so much and no more. We have, therefore, to assume that their perceptions will vary with the number and manner of their accomplishments, and we may almost convince ourselves that each witness who has to give evidence concerning his sense perception should literally undergo examination to make clear his scholarly status and thereby the value of his testimony. Of course, in practice this is not required. First of all, we judge approximately a man's nature and nurture and according to the impression he makes upon us, thence, his intellectual status. This causes great mistakes. But, on the other hand, the testimony is concerned almost always with one or several physical events, so that a simple relational interrogation will establish certainly whether the witness

be

knows and attends to the physical law in question or not. But anyway,
too little is done to determine the means a man uses to reach a certain
perception. If instantaneous contradictions appear, there is little damage,
for in the absence of anything certain, further inferences are fortunately
made in rare cases only. But when the observation is that of one person
alone, or even when more testify but have accidentally the same amount
of knowledge and hence have made the same mistake, and no contradiction
appears, we suppose ourselves to possess the precise truth, confirmed by
several witnesses, and we argue merrily on the basis of it. In the mean-
time we quite forget that contradictions are our salvation from the trusting
acceptance of untruth
and that the absence of contradiction means, as
a rule, the absence of a starting point for further examination. For this
reason and others modern psychology requires us to be cautious.

Among the others is the circumstance that perceptions are rarely pure. Their purity consists in containing nothing else than perception; they are mixed when they are connected with imaginations, judgments, efforts, and volitions. How rarely a perception is pure I have already tried to show; judgments almost always accompany it. I repeat, too, that owing to this circumstance and our ignorance of it, countless testimonies are interpreted altogether falsely. . . .

The individuality of the particular person makes the perception in a still greater degree individual, and makes it almost the creature of him who perceives. . . . The variety is still further increased by means of the comprehensive activity which Fischer presupposes. "Visual per

ception has a comprehensive or compounding activity. We never see any absolute simple and hence do not perceive the elements of things. We see merely a spatial continuum, and that is possible only through comprehensive activity - especially in the case of movement in which the object of movement and the environment must both be perceived." But each individual method of "comprehension" is different. And it is uncertain whether this is purely physical, whether only the memory assists (so that the attention is biased by what has been last perceived), whether imagination is at work or an especial psychical activity must be presupposed in compounding the larger elements. The fact is that men may perceive an enormous variety of things with a single glance. And generally the perceptive power will vary with the skill of the individual. The narrowest, smallest, most particularizing glance is that of the most foolish; and the broadest, most comprehensive, and comparing glance, that of the most wise. This is particularly noticeable when the time of observation is

The one has perceived little and generally the least important; the other has in the same time seen everything from top to bottom and has distinguished between the important and the unimportant, has observed the former rather longer than the latter, and is able to give a better description of what he has seen. And then, when two so different descriptions come before us, we wonder at them and say that one of them is untrue. . . In the variety of perception lies the power of presentation (in our sense of the term). . . .

In this connection there are several more conditions pertaining to general sense perception. First of all there is that so-called vicariousness of the senses which substitutes one sense for another, in representation. The

actual substitution of one sense by another as that of touch and sight, does not belong to the present discussion. The substitution of sound and sight is only apparent. E.g. when I have several times heard the halfnoticed voice of some person without seeing him, I will imagine a definite face and appearance which are pure imagination. So, again, if I hear cries for help near some stream, I see more or less clearly the form of a drowning person, etc. It is quite different in touching and seeing; if I touch a ball, a die, a cat, a cloth, etc., with my eyes closed, then I may so clearly see the color of the object before me that I might be really seeing it. But in this case there is a real substitution of greater or lesser degree. .

The vicariousnesses of visual sensations are the most numerous and the most important. Anybody who has been pushed or beaten, and has felt the blows, will, if other circumstances permit and the impulse is strong enough, be convinced that he has seen his assaulter and the manner of the assault. Sometimes people who are shot at will claim to have seen the flight of the ball. And so again they will have seen in a dark night a comparatively distant wagon, although they have only heard the noise it made and felt the vibration. It is fortunate that, as a rule, such people try to be just in answering to questions which concern this substitution of one sense perception for another. And such questions ought to be urgently put. . .

Still more significant is that characteristic phenomenon, to us of considerable importance, which might be called retrospective illumination of perception. It consists in the appearance of a sense perception under conditions of some noticeable interruption, when the stimulus does not, as a rule, give rise to that perception. . . . In a case in court, there was a shooting in some house and an old peasant woman, who was busy sewing in the room, asserted that she had just before the shooting heard a few steps in the direction from which the shot must have come. Nobody would agree that there was any reason for supposing that the person in question should have made his final steps more noisily than his preceding ones. But I am convinced that the witness told the truth. The steps of the new arrival were perceived subconsciously; the further disturbance of the perception hindered her occupation and finally, when she was frightened by the shot, the upper levels of consciousness were illuminated and the noises which had already reached the subconsciousness passed over the threshold and were consciously perceived.

I learned from an especially significant case, how the same thing could happen with regard to vision. A child was run over and killed by a careless coachman. A pensioned officer saw this through the window. His description was quite characteristic. It was the anniversary of a certain battle. The old gentleman, who stood by the window thinking about it and about his long-dead comrades, was looking blankly out into the street. The horrible cry of the unhappy child woke him up and he really began to see. Then he observed that he had in truth seen everything that had happened before the child was knocked over i.e. for some reason the coachman had turned around, turning the horses in such a way at the same time that the latter jumped sidewise upon the frightened child, and hence the accident. The general expressed himself correctly in this fashion: "I saw it all, but I did not perceive and know that I saw it until after the

scream of the child." . . . His story was confirmed by other witnesses. This psychological process is of significance in criminal trials.

(b) Mistakes of the Senses; Illusions. As sensation is the basis of knowledge, the sensory process must be the basis of the correctness of legal procedure. The information we get from our senses and on which we construct our conclusion, may be said, all in all, to be reliable, so that we are not justified in approaching things we assume to depend on sense perception with exaggerated caution. Nevertheless, this perception is not always completely correct, and the knowledge of its mistakes must help us and even cause us to wonder that we make no greater ones.

Psychological examination of sense perception has been going on since Heraclitus. Most of the mistakes discovered have been used for various purposes, from sport to science. They are surprising and attract and sustain public attention; they have, hence, become familiar, but their influence upon other phenomena and their consequences in the daily life have rarely been studied. For two reasons. First, because such illusions seem to be small and their far-reaching effects are rarely thought of, as when, e.g., a line drawn on paper seems longer or more inclined than it really is. Secondly, it is supposed that the influence of sensory illusions cannot easily make a difference in practical life. If the illusion is observed, it is thereby rendered harmless and can have no effect. If it is not observed and later on leads to serious consequences, their cause cannot possibly be sought out, because it cannot be recognized as such. . . .

Witnesses do not of course know that they have suffered from illusions of sense; we rarely hear them complain of it, anyway. And it is for this very reason that the criminalist must seek it out. The requirement involves great difficulties, for we get very little help from the immense literature on the subject. There are two roads to its fulfillment. In the first place, we must understand the phenomenon as it occurs in our work, and by tracing it back determine whether and which illusion of the sense may have caused an abnormal or otherwise unclear fact. The other road is the theoretical one, which must be called, in this respect, the preparatory road. It requires our mastery of all that is known of sense illusion and particularly of such examples of its hidden nature as exist. Much of the material of this kind is, however, irrelevant to our purpose, particularly all that deals with disease and lies in the field of medicine. It is indubitable that we make many observations in which we get the absolute impression that matters of sensory illusion which do not seem to concern us lie behind some witnesses' observations, etc., although we cannot accurately indicate what they are. The only thing to do when this occurs is either to demonstrate the possibility of their presence or to wait for some later opportunity to test the witness for them.

The apparently most.
But as the bound-

Classification will ease our task a great deal. important divisions are those of normal and abnormal. ary between them is indefinite, it would be well to consider that there is a third class which cannot fall under either heading. This is a class where especially a group of somatic conditions either favor or cause illusory sense perceptions, e.g. a rather over-loaded stomach, a rush of blood to the head, a wakeful night, physical or mental overexertion. . . .

Another question is the limit at which illusions of sense begin, how, in