SCIENTIFIC DETECTION OF CRIME — SANNIE 349 



the men of our service work out from the prints the various stages in 

 the tragedy, determining how the murderer fired the two shots. They 

 return to the scene of the crime a few days afterward to complete 

 their observations and draw a full plan. They then note, on one of the 

 photographs taken that day, that there is, in the room in which the 

 tragedy occurred, a chair which had not previously been there. On 

 that chair, which had been deliberately removed immediately after 

 the murder, they find traces of the passage of a projectile. These 

 marks make it possible to show that the murderer's statements during 

 the reconstruction of the crime were untrue, and to establish how the 

 events actually occurred. 



The scene of a crime cannot, however, be photographed in the same 

 way as for ordinary purposes ; and ordinary cameras arc quite inade- 

 quate. The scenes of crimes vary so much, are so differently lighted, 

 and so different in size, that photographers and camera manufacturers 

 have to satisfy unusual and sometimes conflicting demands. The need 

 to use the photographs, or some of them, as evidence at a later date 

 makes it essential that all the details shall be sufficiently clearly defined 

 to allow of considerable enlargement. 



All advances in the technique of lighting make the work of the 

 police easier; and the development of suitable cameras and lenses 

 gives rise to very complicated problems. Difficult research has been 

 necessary to obtain lenses with an angle of field greater than 90°, an 

 adequate relative aperture, and a suitable depth of field. 



If the photographic document is to do all that is required of it, we 

 must be able, with its help, to reconstruct the dimensions of the objects 

 shown in it. Since 1903, when Bertillon first devised a camera and a 

 method of reconstruction intended for use at the scene of crimes, 

 several not entirely satisfactory ways of solving this problem have 

 been suggested. It was never fully solved until the progress of stereo- 

 photogrammetry furnished the photographer with cameras and plot- 

 ting devices suitable for detective work. The Swiss police are equipped 

 with stereophotogrammeters and automatic plotting devices (auto- 

 graphs) ; these are extremely useful, particularly in cases of motor 

 accidents, for they make it possible, with only two photographs, to re- 

 construct a complete plan of the scene, showing measurements, the 

 position of the vehicles, any marks on the ground, etc. 



Even without using complicated and expensive autographs, it is 

 possible, by more or less simple methods of geometrical reconstruc- 

 tion, to work out the measurements of traces found on the ground or 

 on walls. 



The author of an advertising leaflet reproduced in it a photogi'aph 

 of a building and he claimed that it was a nursing home in which he 

 cured cancer by a special method of his own. On the fagade of the 

 building, there was an enormous inscription confirming his claim. 



