SCIENTIFIC DETECTION OF CRIME — SANNIE 343 



or "No" and, by comparing the physiological reactions to "pertinent" 

 and "neutral" questions, it is possible to detect untruthful replies to 

 the former. 



It is quite obvious that, in this case, there is no "forcible entry" into 

 the private recesses of the human personality. The subject is free to 

 accept or refuse the tests; he is master of his own replies, and only his 

 physiological reactions can betray him. If the test is to be of any 

 value, there must be no coercion, and it has in fact never been sug- 

 gested that there should be. Further, it should be noted that this 

 method does not result in a definite confession, but leads to it indirectly 

 by proving that the individual questioned has lied ; the guilty party's 

 ultimate confession is thus only a consequence of the test. 



This form of interrogation with the help of a polygraph has been 

 studied in particular by Prof. F. E. Inbau, of Northwestern Uni- 

 versity. In the United States of America today, some 60 police serv- 

 ices and various private institutions, as well as the army, use Keeler's 

 polygraph to detect falsehoods and test their employees. According 

 to Keeler and Inbau, successful results have been achieved in over 80 

 percent of cases ; it would thus appear to be an extremely effective test. 



The use of this method has, however, given rise to a certain amount 

 of criticism. Some particularly phlegmatic individuals do not show 

 the normal reflexes when telling a lie. Others, on the other hand, are 

 overemotional and the reflexes of these may be misinterpreted. How- 

 ever, no method of interrogation is infallible, and so far no apparatus 

 which will guarantee 100 percent success can be conceived. It is never- 

 theless striking that even a thorough knowledge of the instrument does 

 not enable an experienced subject to prevent it from betraying him. 

 For example, a student who had had a great deal of experience of this 

 apparatus was one day suspected of theft. Despite all the care which 

 he took over lying and controlling his reactions, the polygraph de- 

 tected his lies; it was subsequently proved by the investigation that 

 he had, in fact, stolen. 



Should the polygraph therefore now be employed generally in crim- 

 inal investigation ? There is no doubt that this instrument is particu- 

 larly valuable from the standpoint of research. However, its employ- 

 ment calls for highly competent interrogators, and it does not seem 

 that it can be put into general use before the latter have acquired the 

 necessary experience. 



In any case, the polygraph marks the introduction of purely scien- 

 tific methods into the examination process — methods which will cer- 

 tainly end, one day, by transforming and simplifying it, while 

 increasing its probative value. The past 20 years show, in this respect, 

 an evolution parallel to that which, as we shall now see, has taken 

 place in the realm of facts. 



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