358 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1954 



niicrocliemical analysis enable us to detect, in such holes, the few 

 thousandths of a milligram of metal left behind by the bullet as it 

 passes through the material. When this degree of accuracy is called 

 for, absolute reliability in the physical or chemical methods used is 

 essential. A microcliemical reaction of mercury, for instance, which 

 is very specific, will detect less than one-millionth of a milligram of 

 mercury. By this means we can trace the mercury derived from the 

 fulminate of a cartridge cap to a distance of more than 30 inches from 

 the mouth of the barrel of a weapon. The following is a very inter- 

 esting instance of the use of this method. 



A man is found dead in bed with two bullet wounds — one in the 

 heart, from which he must have died almost immediately, and the 

 other a mere flesh wound in the abdomen. The weapon lies at the foot 

 of the bed, the last cartridge fired being jammed in the ejection open- 

 ing; the other cartridge is found on the ground. The first investiga- 

 tors, when collecting the cartridges, have mixed them up so that it is 

 no longer possible to say which was jammed in the weapon and was 

 therefore the last fired. The two bullets are found during the autopsy 

 and it is easy to determine which came from which cartridge case, 

 since one is of American and the other of Belgian manufacture. What 

 the investigators have to determine, however, is the order in which the 

 two shots were fired. In the case of a suicide, the fatal shot could only 

 be the second ; if the fatal shot was the first, it was obviously not a case 

 of suicide, since the man could hardly kill himself before wounding 

 himself. 



In an attempt to identify the cartridge first fired, we investigated 

 the mercury in the barrel of the weapon. As we have just said, one 

 of the cartridges was of American origin, and we verified that the 

 cartridge caps of this type of ammunition were made of lead nitride. 

 The other cartridge, which was of Belgian make, had a fulminate of 

 mercury cap. Comparative experiments showed that, if two shots 

 were fired from the same weapon, using one cartridge with a lead 

 nitride cap and one with a fulminate of mercury cap, the quantity of 

 mercury found in the barrel was much greater when the fulminate 

 cartridge was fired last. We were thus able to reconstruct what had 

 happened and to show that the fatal shot was indeed the first, so that 

 suicide was almost excluded. 



We could quote many other examples. The one we have given shows 

 tliat we should always try to solve a scientific problem of detection, 

 oven when it seems insoluble, so long as a sufficiently sensitive and 

 specific method of analysis is available. 



In the scientific detection of crime, we are therefore constantly on 

 the lookout for new methods developed in pure science laboratories. 



