Classics in the History of Psychology

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Christopher D. Green
York University, Toronto, Ontario

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On the Witness Stand:
Essays on Psychology and Crime

Hugo Münsterberg (1908/1925)


LAST summer I had to face a jury as witness in a trial. While I was with my family at the seashore my city house had been burglarised and I was called upon to give an account of my findings against the culprit whom they had caught with a part of the booty. I reported under oath that the burglars had entered through a cellar window, and then described what rooms they had visited. To prove, in answer to a direct question, that they had been there at night, I told that I had found drops of candle wax on the second floor. To show that they intended to return, I reported that they had left a large mantel clock, packed in wrapping paper, on the dining-room table. Finally, as to the amount of clothes which they had taken, I asserted that the burglars did not get more than a specified list which I had given the police.

Only a few days later I found that every one of these statements was wrong. They had not entered through the window, but had broken the [p. 40] lock of the cellar door; the clock was not packed by them in wrapping paper, but in a tablecloth; the candle droppings were not on the second floor, but in the attic; the list of lost garments was to be increased by seven more pieces; and while my story under oath spoke always of two burglars, I do not know that there was more than one. How did all those mistakes occur? I have no right to excuse myself on the plea of a bad memory. During the last eighteen years I have delivered about three thousand university lectures. For those three thousand coherent addresses I had not once a single written or printed line or any notes whatever on the platform; and yet there has never been a moment when I have had to stop for a name or for the connection of the thought. My memory serves me therefore rather generously. I stood there, also, without prejudice against the defendant. Inasmuch as he expects to spend the next twelve years at a place of residence where he will have little chance to read my writings, I may confess frankly that I liked the man. I was thus under the most favourable conditions for speaking the whole truth and nothing but the truth, and, as [p. 41] there is probably no need for the assurance of my best intentions, I felt myself somewhat alarmed in seeing how many illusions had come in.

Of course, I had not made any careful examination of the house. I had rushed in from the seashore as soon as the police notified me, in the fear that valuable contents of the house might have been destroyed or plundered. When I saw that they had treated me mildly, inasmuch as they had started in the wine cellar and had forgotten under its genial influence, on the whole, what they had come for, I had taken only a superficial survey. That a clock was lying on the table, packed ready to be taken away, had impressed itself clearly on my memory; but that it was packed in a tablecloth had made evidently too slight an impression on my consciousness. My imagination gradually substituted the more usual method of packing with wrapping paper, and I was ready to take an oath on it until I went back later, at the end of the summer vacation. In the same way I got a vivid image of the candle droppings on the floor, but as, at the moment of the perception, no interest was attached to the peculiar place where I saw them, [p. 42] I slowly substituted in my memory the second door for the attic, knowing surely from strewn papers and other disorder that they had ransacked both places. As to the clothes, I had simply forgotten that I had put several suits in a remote wardrobe; only later did I find it empty. My other two blunders clearly arose under the influence of suggestion. The police and every one about the house had always taken as a matter of course that the entrance was made by a cellar window, as it would have been much more difficult to use the locked doors. I had thus never examined the other hypothesis, and yet it was found later that they did succeed in removing the lock of a door. And finally, my whole story under oath referred to two burglars, without any doubt at the moment. The fact is, they had caught the gentleman in question when he, a few days later, plundered another house. He then shot a policeman, but was arrested, and in his room they found a jacket with my name written in it by the tailor. That alone gave a hint that my house also had been entered; but from the first moment he insisted that there had been two in this burglary and that the other [p. 43] man had the remainder of the booty. The other has not been found, and he probably still wears my badges; but I never heard any doubt as to his existence, and thus, in mere imitation, I never doubted that there was a companion, in spite of the fact that every part of the performance might just as well have been carried out by one man alone; and, after all, it is not impossible that he should lie as well as shoot and steal.

In this way, in spite of my best intentions, in spite of good memory and calm mood, a whole series of confusions, of illusions, of forgetting, of wrong conclusions, and of yielding to suggestions were mingled with what I had to report under oath, and my only consolation is the fact that in a thousand courts at a thousand places all over the world, witnesses every day affirm by oath in exactly the same way much worse mixtures of truth and untruth, combinations of memory and of illusion, of knowledge and of suggestion, of experience and wrong conclusions. Not one of my mistakes was of the slightest consequence. But is it probable that this is always so? Is it not more natural to suppose that every day errors creep [ p. 44] into the work of justice through wrong evidence which has the outer marks of truth and trust-worthiness? Of course, judge and jury and, later, the newspaper reader try their best to weigh the evidence. Not every sworn statement is accepted as absolute reality. Contradictions between witnesses are too familiar. But the instinctive doubt refers primarily to veracity. The public in the main suspects that the witness lies, while taking for granted that if he is normal and conscious of responsibility he may forget a thing, but it would not believe that he could remember the wrong thing. The confidence in the reliability of memory is so general that the suspicion of memory illusions evidently plays a small rôle in the mind of the juryman, and even the cross-examining lawyer is mostly dominated by the idea that a false statement is the product of intentional falsehood.

All this is a popular illusion against which modern psychology must seriously protest. Justice would less often miscarry if all who are to weigh evidence were more conscious of the treachery of human memory. Yes, it can be said that, while the court makes the fullest use of all the modern scientific [p. 45] methods when, for instance, a drop of dried blood is to be examined in a murder case, the same court is completely satisfied with the most unscientific and haphazard methods of common prejudice and ignorance when a mental product, especially the memory report of a witness, is to be examined. No juryman would be expected to follow his general impressions in the question as to whether the blood on the murderer's shirt is human or animal. But he is expected to make up his mind as to whether the memory ideas of a witness are objective reproductions of earlier experience or are mixed up with associations and suggestions. The court proceeds as if the physiological chemistry of blood examination had made wonderful progress, while experimental psychology, with its efforts to analyse the mental faculties, still stood where it stood two thousand years ago.

The fact is that experimental psychology has not only in general experienced a wonderful progress during the last decades, but has also given in recent years an unusual amount of attention to just those problems which are involved on the witness stand. It is perhaps no exaggeration [p. 46] to say that a new special science has even grown up' which deals exclusively with the reliability of memory. It started in Germany and has had there for some years even a magazine of its own. But many investigations in France and the United States tended from the start in the same direction, and the work spread rapidly over the psychological laboratories of the world. Rich material has been gathered, and yet practical jurisprudence is, on the whole, still unaware of it; and while the alienist is always a welcome guest in the court room, the psychologist is still a stranger there. The Court would rather listen for whole days to the "science" of the handwriting experts than allow a witness to be examined with regard to his memory and his power of perception, his attention and his associations, his volition and his suggestibility, with methods which are in accord with the exact work of experimental psychology. It is so much easier everywhere to be satisfied with sharp demarcation lines and to listen only to a yes or no; the man is sane or insane, and if he is sane, he speaks the truth or he lies. The psychologist would upset this satisfaction completely.

[p. 47] The administration of an oath is partly responsible for the wrong valuation of the evidence. Its seriousness and solemnity suggest that the conditions for complete truth are given if the witness is ready not to lie. We are too easily inclined to confuse the idea of truth in a subjective and in an objective sense. A German proverb says, "Children and fools speak the truth," and with it goes the old "In vino veritas." Of course, no one can suppose that children, fools, and tipsy men have a deeper insight into true relations than the sober and grown-up remainder of mankind. What is meant is only that all the motives are lacking which, in our social turmoil, may lead others to the intentional hiding of the truth. Children do not suppress the truth, because they are naïve; the fools do not suppress it, because they are reckless; and the mind under the influence of wine does not suppress it, because the suppressing mechanism of inhibition is temporarily paralysed by alcohol. The subjective truth may thus be secured, and yet the idle talk of the drunkard and the child and the fool may be objectively untrue from beginning to end. It is in this way only that the oath by its religious [p. 48] background and by its connection with threatened punishment can work for truth. It can and will remove to a high degree the intention to hide the truth, but it may be an open question to what degree it can increase the objective truthfulness.

Of course, everyone knows that the oath helps in at least one more direction in curbing misstatements. It not only suppresses the intentional lie, but it focusses the attention on the details of the statement. It excludes the careless, hasty, chance recollection, and stirs the deliberate attention of the witness. He feels the duty of putting his best will into the effort to reproduce the whole truth and nothing but the truth. No psychologist will deny this effect. He will ask only whether the intention alone is sufficient for success and whether the memory is really improved in every respect by increased attention. We are not always sure that our functions run best when we concentrate our effort on them and turn the full light of attention on the details. We may speak fluently, but the moment we begin to give attention to the special movements of our lips and of our tongue in speaking [p. 49] and make a special effort to produce the movements correctly, we are badly hampered. Is it so sure that our memory works faultlessly simply because we earnestly want it to behave well? We may try hard to think of a name and it will not appear in consciousness; and when we have thought of something else for a long time, the desired name suddenly slips into our mind. May it not be in a similar way that the effort for correct recollection under oath may prove powerless to a degree which public opinion underestimates? And no subjective feeling of certainty can be an objective criterion for the desired truth.

A few years ago a painful scene occurred in Berlin, in the University Seminary of Professor von Liszt, the famous criminologist. The Professor had spoken about a book. One of the older students suddenly shouts, "I wanted to throw light on the matter from the standpoint of Christian morality!" Another student throws in, "I cannot stand that!" The first starts up, exclaiming, "You have insulted me!" The second clenches his fist and cries, "If you say another word --" The first draws a revolver. The second [p. 50] rushes madly upon him. The Professor steps between them and, as he grasps the man's arm, the revolver goes off. General uproar. In that moment Professor Liszt secures order and asks a part of the students to write an exact account of all that has happened. The whole had been a comedy, carefully planned and rehearsed by the three actors for the purpose of studying the exactitude of observation and recollection. Those who did not write the report at once were, part of them, asked to write it the next day or a week later; and others had to depose their observations under cross-examination. The whole objective performance was cut up into fourteen little parts which referred partly to actions, partly to words. As mistakes there were counted the omissions, the wrong additions and the alterations. The smallest number of mistakes gave twenty-six per cent. of [sic] erroneous statements; the largest was eighty per cent. The reports with reference to the second half of the performance, which was more strongly emotional, gave an average of fifteen per cent. more [sic] mistakes than those of the first half. Words were put into the mouths or men who had been [p. 51] silent spectators during the whole short episode; actions were attributed to the chief participants of which not the slightest trace existed; and essential parts of the tragi-comedy were completely eliminated from the memory of a number of witnesses.

This dramatic psychological experiment of six years ago opened up a long series of similar tests in a variety of places, with a steady effort to improve the conditions. The most essential condition remained, of course, always the complete naïveté of the witnesses, as the slightest suspicion on their part would destroy the value of the experiment. It seems desirable even that the writing of the protocol should still be done in a state of belief. There was, for instance, two years ago in Göttingen a meeting of a scientific association, made up of jurists, psychologists, and physicians, all, therefore, men well trained in careful observation. Somewhere in the same street there was that evening a public festivity of the carnival. Suddenly, in the midst of the scholarly meeting, the doors open, a clown in highly coloured costume rushes in in mad excitement, and a negro with a [p. 52] revolver in hand follows him. In the middle of the hall first the one, then the other, shouts wild phrases; then the one falls to the ground, the other jumps on him; then a shot, and suddenly both are out of the room. The whole affair took less than twenty seconds. All were completely taken by surprise, and no one, with the exception of the President, had the slighest [sic] idea that every word and action had been rehearsed beforehand, or that photographs had been taken of the scene. It seemed most natural that the President should beg the members to write down individually an exact report, inasmuch as he felt sure that the matter would come before the courts. Of the forty reports handed in, there was only one whose omissions were calculated as amounting to less than twenty per cent. of the characteristic acts; fourteen had twenty to forty per cent. [sic] of the facts omitted; twelve omitted forty to fifty per cent., and thirteen still more than fifty per cent. But besides the omissions there were only six among the forty which did not contain positively wrong statements; in twenty-four papers up to ten per cent, of the statements were free inventions, [p. 53] and in ten answers -- hat is, in one-fourth of the papers, -- more than ten per cent. [sic] of the statements were absolutely false, in spite of the fact that they all came from scientifically trained observers. Only four persons, for instance, among forty noticed that the negro had nothing on his head; the others gave him a derby, or a high hat, and so on. In addition to this, a red suit, a brown one, a striped one, a coffee-coloured jacket, shirt sleeves, and similar costumes were invented for him. He wore in reality white trousers and a black jacket with a large red necktie. The scientific commission which reported the details of the inquiry came to the general statement that the majority of the observers omitted or falsified about half of the processes which occurred completely in their field of vision. As was to be expected, the judgment as to the time duration of the act varied between a few seconds and several minutes.

It is not necessary to tell more of these dramatic experiments, which have recently become the fashion and almost a sport, and which will still have to be continued with a great variety of conditions [p. 54] if the psychological laws involved are really to be cleared up. There are many points, for instance, in which the results seem still contradictory. In some cases it was shown that the mistakes made after a week were hardly more frequent more than those made after a day. Other experiments seemed to indicate that the number of mistakes steadily increases with the length of time which has elapsed. Again, some experiments suggest that the memory of the two sexes is not essentially different, while the majority of the tests seems to speak for very considerable difference. Experiments with school children, especially, seem to show that the girls have a better memory than the boys as far as omissions are concerned; they forget less. But they have a worse memory than the boys as far as correctness is concerned; they unintentionally falsify more.

We may consider here still another point which is more directly connected with our purpose. A well-known psychologist showed three pictures, rich in detail, but well adapted to the interest of children, to a large number of boys and girls. They looked at each picture for fifteen seconds [p. 55] and then wrote a full report of everything they could remember. After that they were asked to underline those parts of their reports of which they felt so absolutely certain that they would be ready to take an oath before court on the underlined words. The young people put forth their best efforts, and yet the results showed that there were almost as many mistakes in the underlined sentences as in the rest. This experiment has been often repeated and the results make clear that this happens in a smaller and yet still surprising degree in the case of adults also. The grown-up students of my laboratory commit this kind of perjury all the time.

Subtler experiments which were carried on in my laboratory for a long time showed that this subjective feeling of certainty can not only obtain in different degrees, but has, with different individuals, quite different mental structure and meaning. We found that there were, above all, two distinct classes. For one of those types certainty in the recollection of an experience would rest very largely upon the vividness of the image. For the other type it would depend upon the [p. 56] congruity of an image with other previously accepted images; that is, on the absence of conflicts, when the experience judged about is imagined as part of a wide setting of past experiences. But the most surprising result of those studies was perhaps that the feeling of certainty stands in no definite relation to the attention with which the objects are observed. If we turn our attention with strongest effort to certain parts of a complex impression, we may yet feel in our recollection more certain about those parts of which we hardly took notice than about those to which we devoted our attention. The correlations between attention, recollection, and feeling of certainty become the more complex the more we carefully study them. Not only the self-made psychology of the average juryman, but also the scanty psychological statements which judge and attorney find in the large compendiums on Evidence [sic] fall to pieces if a careful examination approaches the mental facts.

The sources of error begin, of course, before the recollection sets in. The observation itself may be defective and illusory; wrong associations [p. 57] may make it imperfect; judgments may misinterpret the experience; and suggestive influences may falsify the data of the senses. Everyone knows the almost unlimited individual differences in the power of correct observation and judgment. Everyone knows that there are persons who, under favourable conditions, see what they are expected to see. The prestidigitateurs, [sic] the fakirs, the spiritualists could not play their tricks if they could not rely on associations and suggestions, and it would not be so difficult to read proofs if we did not usually see the letters which we expect. But we can abstract here from the distortions which enter into the perception itself; we have discussed them before. The mistakes of recollection alone are now the object of our inquiry and we may throw light on them from still another side.

Many of us remember minutes in which we passed through an experience with a distinct and almost uncanny feeling of having passed through it once before. The words which we hear, the actions which we see, we remember exactly that we experienced them a long time ago. The case is rare with men, but with women extremely [p. 58] frequent, and there are few women who do not know the state. An idea is there distinctly coupled with the feeling of remembrance and recognition, and yet it is only an-associated sensation, resulting from fatigue or excitement, and without the slightest objective basis in the past. The psychologist feels no difficulty in explaining it, but it ought to stand as a great warning signal before the minds of those who believe that the feeling of certainty in recollection secures objective truth. There is no new principle involved, of course, when the ideas which stream into consciousness spring from one's own imagination instead of being produced by the outer impressions of our surroundings. Any imaginative thought may slip into our consciousness and may carry with it in the same way that curious feeling that it is merely the repetition of something we have experienced before.

A striking illustration is well known to those who have ever taken the trouble to approach the depressing literature of modern mysticism. There we find an abundance of cases reported which seem to prove that either prophetic fortune [p. 59] tellers or inspired dreams have anticipated the real future of a man's life with the subtlest details and with the most uncanny foresight. But as soon as we examine these wonderful stories, we find that the coincidences are surprising only in those cases in which the dreams and the prophecies have been written down after the realisation. Whenever the visions were given to the protocol before-hand, the percentage of true realisations remains completely within the narrow limits of chance coincidents and natural probability. In other words, there cannot be any doubt that the reports of such prophecies which are communicated after having been realised are falsified. That does not reflect in the least on the subjective veracity; our satisfied client of the clever fortune teller would feel ready to take oath to his illusions of memory; but illusions they remain. He also, in most cases, feels sure that he told the dream to the whole family the next morning exactly as it happened; only when it is possible to call the members of the family to a scientific witness stand, does it become evident that the essentials of the dream varied in all directions from the real later occurrence. The [p. 60] real present occurrence completely transforms the reminiscences of the past prophecy and every happening is apperceived with the illusory overtone of having been foreseen.

We must always keep in mind that a content of consciousness is in itself independent of its relation to the past and has thus in itself no mark which can indicate whether it was experienced once before or not. The feeling of belonging to our past life may associate itself thus just as well with a perfectly new idea of our imagination as with a real reproduction of an earlier state of mind. As a matter of course, the opposite can thus happen, too; that is, an earlier experience may come to our memory stripped of every reference to the past, standing before our mind like a completely new product of imagination. To point again to an apparently mysterious experience: the crystal gazer feels in his half hypnotic state a free play of inspired imagination, and yet in reality he experiences only a stirring up of the deeper layers of memory pictures. They rush to his mind without any reference to their past origin, picturing a timeless truth which is surprisingly correct only [p. 61] because it is the result of a sharpened memory. Yes, we fill the blanks of our perceptions constantly with bits of reproduced memory material and take those reproductions for immediate impressions. In short, we never know from the material itself whether we remember, perceive, or imagine, and in the borderland regions there must result plenty of confusion which cannot always remain without dangerous consequences in the court-room.

Still another phenomenon is fairly familiar to everyone, and only the courts have not yet discovered it. There are different types of memory, which in a very crude and superficial classification might be grouped as visual, acoustical, and motor types. There are persons who can reproduce a landscape or a painting in full vivid colours and with sharp outlines throughout the field, while they would be unable to hear internally a melody or the sound of a voice. There are others with whom every tune can easily resound in recollection and who can hardly read a letter of a friend without hearing his voice in every word, while they are utterly unable to awake an optical [p. 62] image. There are others again whose sensorial reproduction is poor in both respects; they feel intentions of movement, as of speaking, of writing, of acting, whenever they reconstruct past experience. In reality the number of types is much larger. Scores of memory variations can be discriminated. Let your friends describe how they have before their minds yesterday's dinner table and the conversation around it, and there will no be two whose memory shows the same scheme and method. Now we should not ask a short-sighted man for the slight visual details of a far distant scene, yet it cannot be safer to ask a man of the acoustical memory type for strictly optical recollections. No one on the witness stand is to-day examined to ascertain in what directions his memory is probably trustworthy and reliable; he may be asked what he has seen, what he has heard, what he as spoken, how he has acted, and yet even a most superficial test might show that the mechanism of his memory would be excellent for one of these four groups of questions and utterly useless for the others, however solemnly he might keep his oath.

[p. 63] The courts will have to learn, sooner or later, that the individual differences of men can be tested to-day by the methods of experimental psychology far beyond anything which common sense and social experience suggest. Modern law welcomes, for instance, for identification of criminals all the discoveries of anatomists and physiologists as to the individual differences; even the different play of lines in the thumb is carefully registered in wax. But no one asks for the striking differences as to those mental details which the psychological experiments on memory and attention, on feeling and imagination, on perception and discrimination, on judgment and suggestion, on emotion and volition, have brought out in the last decade. Other sciences are less slow to learn. It has been found, for instance, that the psychological speech impulse has for every individual a special character as to intonation and melody. At once the philologists came and made the most brilliant use of this psychological discovery. They have taken, for instance, whole epic texts and examined those lines as to which it was doubtful whether they belonged originally to the poem or were later interpolations. [p. 64] Wherever the speech intonation agreed with that of the whole song, they acknowledged the authentic origin, and where it did not agree they recognised an interpolation of the text. Yet the lawyers might learn endlessly more from the psychologists about individual differences than the philologians [sic] have done. They must only understand that the working of the mental mechanism in a personality depends on the constant coöperation of simple and elementary functions which the modern laboratory experiment can isolate and test. If those simplest elements are understood, their complex combination becomes necessary; just as the whole of a geometrical curve becomes necessary as soon as its analytical formula is understood for the smallest part.

But the psychological assistance ought not to be confined to the discrimination of memory types and other individual differences. The experimentalist cannot forget how abundant are the new facts of memory variations which have come out of experiments on attention and inhibition. We know and can test with the subtlest means the waves of fluctuating attention through which [p. 65] ideas become reinforced and weakened. We know, above all, the inhibitory influences which result from excitements and emotions which may completely change the products of an otherwise faithful memory.

A concrete illustration may indicate the method of the experimenters. The judge has to make up his mind as soon as there is any doubt on which side the evidence on an issue of fact preponderates. If it can be presupposed that both sides intend to speak the truth he is ready to consider that the one side had, perhaps, a more frequent opportunity to watch the facts in question, the other side, perhaps, saw them more recently; the one saw them, perhaps, under especially impressive circumstances, the other, perhaps, with further knowledge of the whole situation, and so on. Of course, his buckram-bound volumes of old decisions guide him, but those decisions report again only that the one or the other judge, relying on his common-sense, thought recency more weighty than frequency, or frequency more important than impressiveness, or perhaps the opposite. It is the same way in which common-sense [p. 66] tells a man what kind of diet is most nourishing. Yet what responsible physician would ignore the painstaking experiments of the physiological laboratory, determining exactly the quantitative results as to the nourishing value of eggs or milk or meat or bread? The judges ignore the fact that with the same accuracy their common-sense can be transformed into careful measurements the results of which may widely differ from haphazard opinion. The psychologist, of course, has to reduce the complex facts to simple principles and elements. An investigation, devoted to this problem of the relative effectiveness of recency, frequency, and vividness was carried on in my psychological laboratory. Here we used simple pairs of coloured papers and printed figures, or colours and words, or words and figures, or colours and forms, and so on. A series of ten such pairs may be exposed successively in a lighted field, each time one colour and one figure of two digits. But one pair, perhaps the third, is repeated as the seventh, and thus impresses itself by its frequency; another pair, perhaps the fifth, comes with impressive vividness, [p. 67] from the fact that instead of two digits, suddenly three are used. The last pair has, of course, the advantage in that it sticks to the mind from its position at the end; it remains the most recent, which is not inhibited by any following pair. After a pause the colours are shown again and every one of the subjects has to write down the figures together with which he believes himself to have seen the particular colours. Is the vivid pair, or the frequently repeated pair, or the recent pair better remembered? Of course, the experiment was made under most different conditions, with different pauses, different material, different length of the series, different influences, different distribution, different subjects, but after some years of work, facts showed themselves which can stand as facts. The relative value of the various conditions for exact recollection became really measurable. They may and must be corrected by further experiments, but they are raised from the first above the level of the chance opinions of the lawyer-psychologist.

All this remains entirely within the limits of the normal healthy individuality. Nothing of all that [p. 68] we have mentioned belongs to the domain of the physician. Where the alienist has to speak, that is, where pathological amnesia destroys the memory of the witness, or where hallucinations of disease, or fixed ideas deprive the witness's remembrance of their value, there the psychologist is not needed. It is in normal mental life and its border-land regions that the progress of psychological science cannot be further ignored. No railroad or ship company would appoint to a responsible post in its service men whose eyesight had not been tested for colour blindness. There may be only one among thirty or forty who cannot distinguish at a distance the red from the green lantern. Yet if he slips into the service without being tested, his slight defect, which does not disturb him in practical life and which he may never have noticed if he was not just picking red strawberries among green leaves, may be sufficient to bring about the most disastrous wrecking of two trains or the most horrible collision of steamers. In the life of justice trains are wrecked and ships are colliding too often, simply because the law does not care to examine the mental colour blindness [p. 69] of the witness's memory. And yet we have not even touched one factor which, more than anything else, devastates memory and plays havoc with our best intended recollections: that is, the power of suggestion.