SCIENTIFIC DETECTION OF CRIME — SANNIE 351 



century and improved at the beginning of the twentieth are giving 

 more and more reliable results. Sensitive as these methods are, how- 

 ever, they all necessitate the taking of fairly large samples from the 

 organs. It is known that arsenic tends to accumulate in the hair and 

 nails; the quantity of arsenic found in a tuft of hair, at a given point, 

 enables us to ascertain the time when the poison was administered, 

 since we know the speed at which the hair grows (slightly over half 

 an inch in a month). The chemical methods previously available, 

 however, necessitated considerable quantities of hair, from half an 

 inch to a few inches long, and therefore covering a period of one or 

 more months. The development of atomic piles has now provided 

 toxicologists with a neat and infinitely more accurate means of tracing 

 acute or chronic arsenical poisoning. This method, as described by 

 GriU'on and Barbaud, consists in rendering the arsenic contained in 

 the substance of the hair itself artificially radioactive by exposing the 

 hair to the flux of thermic neutrons produced by an atomic pile. Sub- 

 sequent analysis of the radiation from the hair enables us, first, to 

 identify the element by measuring its period and, second, to determine 

 its situation in relation to the length of the hair. It is thus possible, 

 without in any way damaging the sample taken from the living or 

 the dead body, to ascertain the date at which the poison was absorbed, 

 and to trace the course of its impregnation of the organism. 



Such developments are very common in forensic science investiga- 

 tion. We have been able to identify blood for a long time past ; but 

 since microspectroscopes have been introduced and improved, we have 

 been able to identify extremely small quantities (much less than a 

 milligram) with absolute certainty. It is useful, of course, to know 

 that a stain has been made by human blood, but that does not tell us 

 whose blood it is. Is it possible to discover individual characteristics 

 in the blood by which we can answer this question? The research 

 done, over the past 15 years, on blood groups has been the first step 

 toward the solution of this problem. When these methods are applied 

 to dry bloodstains, they help us to decide whether a stain found on 

 the clothing of an accused person may have come from the victim or 

 from the accused himself. 



The research done on the theory of blood groups in human beings 

 has revealed an ever-increasing number of specific factors in the blood, 

 which are inherited according to Mendelian laws. Up to last year, 

 the only blood groups covered by the methods of investigation used 

 on dry bloodstains were the classic A, B, and O groups. Quite re- 

 cently, similar methods have been applied to the Rh factor, and there 

 is little doubt that in future they will be applied in many other ways. 



When scientific methods are introduced, the provisions of a penal or 

 a civil code, drawn up at a time when such ideas were entirely un- 



