criminal psychology-第46节
按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
s； but are simply observations statistically made concerning the number of rainy days； the case is quite different。 The distinction between these two cases is of importance to the criminalist because the substitution of one for the other； or the confusion of one with the other； will cause him to confuse and falsely to interpret the probability before him。 Suppose； e。 g。； that a murder has happened in Vienna； and suppose that I declare immediately after the crime and in full knowledge of the facts； that according to the facts； i。 e。； according to the conditions which lead to the discovery of the criminal； there is such and such a degree of probability for this discovery。 Such a declaration means that I have calculated a conditioned probability。 Suppose that on the other hand； I declare that of the murders occurring in Vienna in the course of ten years； so and so many are unexplained with regard to the personality of the criminal； so and so many were explained within such and such a time；and consequently the probability of a discovery in the case before us is so and so great。 In the latter case I have spoken of unconditioned probability。 Unconditioned probability may be studied by itself and the event compared with it； but it must never be counted on； for the positive cases have already been reckoned with in the unconditioned percentage； and therefore should not be counted another time。 Naturally； in practice； neither form of probability is frequently calculated in figures； only an approximate interpretation of both is made。 Suppose that I hear of a certain crime and the fact that a footprint has been found。 If without knowing further details； I cry out： ‘‘Oh！ Footprints bring little to light！'' I have thereby asserted that the statistical verdict in such cases shows an unfavorable percentage of unconditional probability with regard to positive results。 But suppose that I have examined the footprint and have tested it with regard to the other circumstances； and then declared： ‘‘Under the conditions before us it is to be expected that the footprint will lead to results'' then I have declared； ‘‘According to the conditions the conditioned probability of a positive result is great。'' Both assertions may be correct； but it would be false to unite them and to say； ‘‘The conditions for results are very favorable in the case before us； but generally hardly anything is gained by means of footprints； and hence the probability in this case is small。'' This would be false because the few favorable results as against the many unfavorable ones have already been considered； and have already determined the percentage； so that they should not again be used。
Such mistakes are made particularly when determining the complicity of the accused。 Suppose we say that the manner of the crime makes it highly probable that the criminal should be a skilful； frequently…punished thief； i。 e。； our probability is conditioned。 Now we proceed to unconditioned probability by saying： ‘‘It is a well…known fact that frequently…punished thieves often steal again； and we have therefore two reasons for the assumption that X； of whom both circumstances are true； was the criminal。'' But as a matter of fact we are dealing with only one identical probability which has merely been counted in two ways。 Such inferences are not altogether dangerous because their incorrectness is open to view； but where they are more concealed great harm may be done in this way。
A further subdivision of probability is made by Kirchmann。＇1＇ He distinguished：
＇1＇ ber die Wahrscheinlicbkeit； Leipzig 1875。
（1） General probability； which depends upon the causes or consequences of some single uncertain result； and derives its character from them。 An example of the dependence on causes is the collective weather prophecy； and of dependence on consequences is Aristotle's dictum； that because we see the stars turn the earth must stand still。 Two sciences especially depend upon such probabilities： history and law； more properly the practice and use of criminal law。 Information imparted by men is used in both sciences； this information is made up of effects and hence the occurrence is inferred from as cause。
（2） Inductive probability。 Single events which must be true； form the foundation； and the result passes to a valid universal。 （Especially made use of in the natural sciences； e。 g。； in diseases caused by bacilli； in case X we find the appearance A and in diseases of like cause Y and Z； we also find the appearance A。 It is therefore probable that all diseases caused by bacilli will manifest the symptom A。）
（3） Mathematical Probability。 This infers that A is connected either with B or C or D； and asks the degree of probability。 I。 e。： A woman is brought to bed either with a boy or a girl： therefore the probability that a boy will be born is one…half。
Of these forms of probability the first two are of equal importance to us； the third rarely of value； because we lack arithmetical cases and because probability of that kind is only of transitory worth and has always to be so studied as to lead to an actual counting of cases。 It is of this form of probability that Mill advises to know； before applying a calculation of probability； the necessary facts； i。 e。； the relative frequency with which the various events occur； and to understand clearly the causes of these events。 If statistical tables show that five of every hundred men reach； on an average； seventy years； the inference is valid because it expresses the existent relation between the causes which prolong or shorten life。
A further comparatively self…evident division is made by Cournot； who separates subjective probability from the possible probability pertaining to the events as such。 The latter is objectively defined by Kries＇1＇ in the following example：
＇1＇ J。 v。 Kries： ber die Wahrseheinlichkeit Il。 Mglichkeit u。 ihre Bedeutung in Strafrecht。 Zeitschrift f。 d。 ges。 St。 R。 W。 Vol。 IX； 1889。
‘‘The throw of a regular die will reveal； in the great majority of cases； the same relation； and that will lead the mind to suppose it objectively valid。 It hence follows； that the relation is changed if the shape of the die is changed。'' But how ‘‘this objectively valid relation；'' i。 e。； substantiation of probability； is to be thought of； remains as unclear as the regular results of statistics do anyway。 It is hence a question whether anything is gained when the form of calculation is known。
Kries says； ‘‘Mathematicians； in determining the laws of probability； have subordinated every series of similar cases which take one course or another as if the constancy of general conditions； the independence and chance equivalence of single events； were identical throughout。 Hence； we find there are certain simple rules according to which the probability of a case may be calculated from the number of successes in cases observed until this one and from which； therefore； the probability for the appearance of all similar cases may be derived。 These rules are established without any exception whatever。'' This statement is not inaccurate because the general applicability of the rules is brought forward and its use defended in cases where the presuppositions do not agree。 Hence； there are delusory results； e。 g。； in the calculation of mortality； of the statements of witnesses and judicial deliverances。 These do not proceed according to the schema of the ordinary play of accident。 The application； therefore； can be valid only if the constancy of general conditions may be reliably assumed。
But this evidently is valid only with regard to unconditioned probability which only at great intervals and transiently may influence our practical work。 For； however well I may know that according to statistics every xth witness is punished for perjury； I will not be frightened at the approach of my xth witness though he is likely； according to statistics； to lie。 In such cases we are not fooled； but where events are confused we still are likely to forget that probabilities may be counted only from great series of figures in which the experiences of individuals are quite lost。
Nevertheless figures and the conditions of figures with regard to probability exercise great influence upon everybody； so great indeed； that we really must beware of going too far in the use of figures。 Mill cites a case of a wounded Frenchman。 Suppose a regiment made up of 999 Englishmen and one Frenchman is attacked and one man is wounded。 No one would believe the account that this one Frenchman was the one wounded。 Kant says significantly： ‘‘If anybody sends his doctor 9 ducats by his servant； the doctor certainly supposes that the servant has either lost or otherwise disposed of one ducat。'' These are merely probabilities which depend upon habits。 So； it may be supposed that a handkerchief has been lost if only eleven are found； or people may wonder at the doctor's ordering a tablespoonful every five quarters of an hour； or if a job is announced with 2437 a year as salary。
But just as we presuppose that wherever the human will played any part； regular forms will come to light； so we begin to doubt that such forms will occur where we find that
