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Section 26. (d) The Empirical Method in the Study of Cases.

Properly to bound our discussion of Humian skepticism, a few words have to be said concerning the empirical method of the sciences. We will call those laws purely empirical which, in the study of nature, yield regularities that are demonstrated by observation and experiment, but upon which little or no reliance is placed with regard to cases which differ considerably from the observed. The latter is done because no reason is seen for the existence of such laws. The empirical rule is, therefore, no final law, but is capable of explaining, especially when true, e. g., the succession of a certain condition of weather from certain meteorological signs, the improvement of species through crossing, the fact that some alloys are harder than their components, and so on. Or, to choose examples from our own field, jurisprudence may assert as empirical law that a murderer is a criminal who has gone unpunished for his earlier crimes; that all gamblers show such significant resemblances; that the criminal who has soiled his hands with blood in some violent

crime was accustomed to wipe them on the underside of a table; that the slyest person generally perpetrates some gross stupidity after committing a serious crime, and so renders discovery simpler; that lust and cruelty have a certain relation; that superstition plays a great rôle in crime, etc.

It is of exceeding importance to establish such purely empiric laws in our science, which has done little with such matters because, owing to scanty research into most of them, we need these laws. We know approximately that this and that have come to light so and so often, but we have not reduced to order and studied systematically the cases before us, and we dare not call this knowledge natural law because we have subjected it to no inductive procedure. "The reference of any fact discovered by experience to general laws or rules we call induction. It embraces both observation and deduction." Again, it may be defined as "the generalization or universalization of our experiences; and inference that a phenomenon occurring x times will invariably occur when the essential circumstances remain identical. The earliest investigators started with the simplest inductions,—that fire burns, that water flows downward,—so that new, simple truths were continually discovered. This is the type of scientific induction and it requires further, the addition of certainty and accuracy."[1]

The foregoing might have been written expressly for us lawyers, but we have to bear in mind that we have not proceeded in our own generalizations beyond "fire burns, water flows downward." And such propositions we have only derived from other disciplines. Those derived from our own are very few indeed, and to get more we have very far to go. Moreover, the laws of experience are in no way so certain as they are supposed to be, even when mathematically conceived. The empirical law is established that the sum of the three angles of a triangle is equal to two right angles. And yet nobody, ever since the science of surveying has been invented, has succeeded in discovering 180 degrees in any triangle. Now then, when even such things, supposed ever since our youth to be valid, are not at all true, or true theoretically only, how much more careful must we be in making inferences from much less certain rules, even though we have succeeded in using them before in many analogous cases? The activity of a criminalist is of far too short duration to permit him to experience any more than a very small portion of the possibilities of life, and suggestions from foreign sources are very

rare. The situation is different in other disciplines. "Our experience," says James Sully,"[2] enables us to express a number of additional convictions. We can predict political changes and scientific developments, and can conceive of the geographical conditions at the north pole." Other disciplines are justified to assert such additional propositions, but is ours? A man may have dealt for years with thieves and swindlers, but is he justified in deducing from the inductions made in his experience, the situation of the first murderer he deals with? Is he right in translating things learned by dealing with educated people to cases where only peasants appear? In all these cases what is needed in making deductions is great caution and continual reminder to be very careful, for our work here still lacks the proper material. In addition we have to bear in mind that induction is intimately related to analogy. According to Lipps[3] the ground of one is the ground of the other; they both rest on the same foundation. "If I am still in doubt whether the fact on which a moment ago I depended as the sufficient condition for a judgment may still be so regarded, the induction is uncertain. It is unjustified when I take for sufficiently valid something that as a matter of fact ought not to be so taken." If we bear in mind how much we are warned against the use of analogy, how it is expressly excluded in the application of certain criminal laws, and how dangerous the use of every analogy is, we must be convinced that the use for our cases of both induction and analogy, is always menace. We have at the same time to bear in mind how much use we actually make of both; even our general rules—e. g., concerning false testimony,—bias, reversibility, special inclinations, etc.— and our doctrines concerning the composition and indirection of testimony, even our rules concerning the value of witnesses and confessions, all these depend upon induction and analogy. We pass by their use in every trial from case to case. A means so frequently and universally used must, however, be altogether reliable, or be handled with the greatest care. As it is not the first it must be handled in the second way.

We have yet to indicate the various ways in which induction may be used. Fick has already called attention to the astounding question concluding Mill's system of logic: Why, in many cases, is a single example sufficient to complete induction, while in other

cases myriads of unanimous instances admitting of no single known or suspected exception, make only a small step toward the establishment of a generally valid judgment?

This question is of enormous significance in criminal cases because it is not easy to determine in any particular trial whether we have to deal with a situation of the first sort where a single example is evidential, or a situation of the second sort where a great many examples fail to be evidential. On this difficulty great mistakes depend, particularly mistakes of substitution of the first for the second. We are satisfied in such cases with a few examples and suppose ourselves to have proved the case although nothing whatever has been established.

We must see first of all if it is of any use to refer the difficulty of the matter to the form in which the question is put, and to say: The difficulty results from the question itself. If it be asked, "Are any of the thousand marbles in the bag white marbles?" the question is determined by the first handful, if the latter brings to light a single white marble. If, however, the problem is phrased so: Does the bag contain white marbles only? then, although 999 marbles might already have been drawn from the receptacle, it can not be determined that the last marble of the 1000 is white. In the same way, if people assert that the form of the question determines the answer, it does not follow that the form of the question is itself determined or distinguished inasmuch as the object belongs to the first or the second of the above named categories.

A safe method of distinction consists in calling the first form of the question positive and the second negative. The positive refers to a single unit; the negative to a boundless unit. If then I ask: Are there any white marbles whatever in the bag? the answer is rendered affirmative by the discovery of a single white marble. But if the question is phrased: Are there onlywhite marbles in the bag? merely its form is positive but its intent is negative. To conform the manner of the question to its intent, it would be necessary to ask: Are there no other colors than white among the marbles in the bag? And inasmuch as the negative under given circumstances is in many ways boundless, the question admits of no answer until the last marble has been brought to light. If the total number of marbles is unlimited the question can receive no complete inductive answer in mathematical form; it can be solved only approximately. So again, if one asks: Are there any purely blue birds? the answer is affirmative as soon as a single completely blue bird is brought to

light. But if the question is: Do not also striped birds exist? no answer is possible until the very last bird on earth is exhibited. In that way only could the possibility be excluded that not one of the terrestrial fowls is striped. As a matter of fact we are satisfied with a much less complete induction. So we say: Almost the whole earth has been covered by naturalists and not one of them reports having observed a striped bird; hence there would be none such even in the unexplored parts of the earth. This is an inductive inference and its justification is quite another question.

The above mentioned distinction may be made still clearer if instead of looking back to the form of the question, we study only the answer. We have then to say that positive statements are justified by the existence of a single instance, negative assertions only by the complete enumeration of all possible instances and never at all if the instances be boundless. That the negative proof always requires a series of demonstrations is well known; the one thing which may be firmly believed is the fact that the problem, whether a single example is sufficient, or a million are insufficient, is only a form of the problem of affirmative and negative assertions.

So then, if I ask: Has A ever stolen anything? it is enough to record one judgment against him, or to bring one witness on the matter in order to establish that A committed theft at least once in his life. If, however, it is to be proved that the man has never committed a theft, his whole life must be reviewed point by point, and it must be shown that at no instant of it did he commit larceny. In such cases we are content with much less. We say first of all: We will not inquire whether the man has never stolen. We will see merely whether he was never punished for theft. But here, too, we must beware and not commit ourselves to inquiring of all the authorities in the world, but only of a single authority, who, we assume, ought to know whether A was punished or not. If we go still further, we say that inasmuch as we have not heard from any authorities that the man was ever punished for stealing, we suppose that the man was never punished on that ground; and inasmuch as we have not examined anybody who had seen A steal, we preferably suppose that he has never stolen. This is what we call satisfactory evidence, and with the poor means at our disposal it must suffice.

In most cases we have to deal with mixed evidence, and frequently it has become habitual to change the problem to be solved according to our convenience, or at least to set aside some one thing. Suppose

that the issue deals with a discovered, well-retained footprint of a man. We then suspect somebody and compare the sole of his shoe with the impression. They fit in length and width, in the number of nails and in all the other possible indices, and we therefore assert: It is the footprint of the suspect, for "whose footprint?" is the problem we are troubling ourselves to solve. In truth we have only shown that the particular relations, in the matter of length, breadth, number of nails, etc., agree, and hence we regard the positive part of the evidence as sufficient and neglect the whole troublesome negative part, which might establish the fact that at the time and in the region in question, nobody was or could be whose foot could accurately fit that particular footprint. Therefore we have not proved but have only calculated the probability that at the time there might possibly not have been another person with a shoe of similar length, breadth and number of nails. The probability becomes naturally less as fewer details come to hand. The difficulty lies in finding where such probability, which stands for at least an assumption, must no longer be considered. Suppose, now, that neither shoe-nails nor patches, nor other clear clews can be proved and only length and width agree. If the agreement of the clews were really a substantiation of the proof by evidence, it would have to suffice as positive evidence; but as has been explained, the thing proved is not the point at issue, but another point.

The negative portion of the evidence will naturally be developed with less accuracy. The proof is limited to the assertion that such shoes as were indicated in the evidence were very rarely or never worn in that region, also that no native could have been present that the form of the nails allowed inference of somebody from foreign regions, one of which might be the home of the suspect, etc. Such an examination shows that what we call evidence is only probability or possibility.

Another form which seems to contradict the assertion that negative propositions are infinite is positive evidence in the shape of negation. If we give an expert a stain to examine and ask him whether it is a blood stain, and he tells us: "It is not a blood stain," then this single scientifically established assertion proves that we do not have to deal with blood, and hence "negative" proof seems brought in a single instance. But as a matter of fact we deal here with an actually positive proof, for the expert has given us the deduced proposition, not the essential assertion. He has found the

stain to be a rust stain or a tobacco stain, and hence he may assert and deduce that it is not blood. Even were he a skeptic, he would say, "We have not yet seen the blood of a mammal in which the characteristic signs for recognition were not present, and we have never yet recognized a body without the blood pertaining to it, and hence we may say, we are not dealing with blood because all of us found the characteristics of the stain to be what we have been until now accustomed to call the characteristics of rust stain."

We have still to touch upon the difference between logical connection and experience. If I say, "This mineral tastes salty, therefore it is soluble in water," the inference depends upon logical relationships, for my intent is: "If I perceive a salty taste, it has to be brought to the nerves of taste, which can be done only by the combination of the mineral with the saliva, hence by its solution in the saliva. But if it is soluble in saliva it must also be soluble in water." If I say on the other hand, "This mineral tastes salty, has a hardness of 2, a specific gravity of 2.2, and consequently it crystallizes hexagonally,"—this statement depends on experience, for what I really say is: "I know first of all, that a mineral which has the qualities mentioned must be rock salt; for at the least, we know of no mineral which has these qualities and is not rock salt, and which in the second place crystallizes hexagonally as rock salt does,—a way which, at least, we find rock salt never to have missed." If we examine the matter still more closely we become convinced that in the first case only the formal and logical side, in the second the experiential aspect predominates. The premises of both cases are purely matters of experience and the formal question of inference is a matter of logic. Only,—at one time the first question, at another the second comes more obviously into the foreground. Although this matter appears self-evident it is not indifferent. It is well known that whenever we are powerfully influenced by one thing, things of little intensity are either not experienced at all or only to a very small degree, and are therefore neglected. This is a fact which may indeed be shown mathematically, for infinity plus one equals infinity. When, therefore, we undergo great pain or great joy, any accompanying insignificant pain or any pleasure will be barely felt, just as the horses who drag a very heavy wagon will not notice whether the driver walking beside them adds his coat to the load (cf. Weber's law). Hence, when we criminalists study a difficult case with regard to the question of proof, there are two things to do in order to test the premises for correctness according

to the standards of our other experiences, and to draw logically correct inferences from these premises. If it happens that there are especial difficulties in one direction while by some chance those in the other are easily removed, it becomes surprising how often the latter are entirely ignored. And hence, the adjustment of inferences is naturally false even when the great difficulties of the first type are removed correctly. Therefore, if the establishment of a fact costs a good deal of pains and means the expenditure of much time, the business of logical connection appears so comparatively easy that it is made swiftly and—wrongly.

Mistakes become, at least according to my experience, still more frequent when the difficulty is logical and not empirical. As a matter of honesty, let me say that we criminalists are not trained logicians, however necessary it is that we shall be such, and most of us are satisfied with the barren remainder of what we learned long ago in the Gymnasium and have since forgotten. The difficulties which occur in the more important logical tasks are intelligible when compared with the lesser difficulties; and when one of these larger problems is by good fortune rightly solved, the effort and the work required by the solution make it easy to forget asking whether the premises are correct; they are assumed as self-evident. Hence, in the review of the basis for judgment, it is often discovered that the logical task has been performed with care, with the expenditure of much time, etc., only to be based upon some apparently unessential presupposition which contradicts all experience and is hence materially incorrect. Consequence,—the inference is wrong since the premise was wrong, and the whole work has gone for nothing. Such occurrences convince one that no judge would have been guilty of them if the few difficulties concerning the fact in question were not, because treated in the light of the effort required by the logical work, quite neglected. Nor does this occur unconsciously, or as a consequence of a sort of lapse of memory concerning the meaning or the importance of an empirical problem, it also happens at least half consciously by way of a characteristic psychic process which everybody may identify in his own experience: i. e., the idea occurs, in some degree subconsciously, that the overgreatness of the work done in one direction ought to be corrected by the inadequacy of the work done in the other direction. And this happens in lawyer's work often, and being frequently justifiable, becomes habitual. If I, for example, have examined ten unanimous witnesses concerning the same event and have completely demonstrated

the status of the case, I ought, in examining the last two witnesses, who are perhaps no longer needed but have been summoned and appear, certainly to proceed in a rapid manner. This justifiable neglect is then half unconsciously transferred to other procedures where there is possible no equalization of the hypertrophy of work in one direction with the dwarfing of it in another, and where the mistake causes the result to be wrong. However I may have been bothered by the multiplication of ten groups of factors and whatever accuracy I may have applied to a task can not permit me to relax my attention in the addition of the individual results. If I do I am likely to commit an error and the error renders all the previous labor worthless.

Indeed, it may be asserted that all logic is futile where the premises or a single premise may be wrong. I expect, in truth, that the procedures here described will be doubted to be even possible, but doubters are recommended to examine a few cases for the presence of this sort of thing.