FORENSIC MICROSCOPY 



Fig. 1. A comparison photomicrograph of a silicone rubber reproduction of an evidence tool mark 

 (left) and test tool mark (right). 



tion procedure is fairly standard throughout 

 comparative micrography and the universal 

 instrument employed for this work is the 

 comparison microscope, made up either as a 

 single unit or constructed by spanning two 

 metallurgical microscopes with a comparison 

 bridge. It is necessary that all optics em- 

 ployed be carefully matched as to magnifica- 

 tion and field and in some instances, it is 

 desirable to employ matched vertical il- 

 luminators such as represented by the 

 Ultrapaks shown in Figure 2. For the most 

 part, low magnification of the order of 10 to 

 20 diameters will be employed for this work. 

 For special problems, it is useful to have 

 paired optics capable of producing compara- 

 tive examinations as high as 200 to 300 

 diameter magnification. 



Although the techniques employed in fire- 

 arms identification are similar to, and prob- 

 ably an offshoot of comparative micrography, 

 nevertheless, this technique is usually given 

 separate identity. Firearms identification — 

 or what is popularly, though erroneously, 

 called "ballistics" — entails more than the 

 simple matching of bullets or cartridge cases. 

 For the sake of simplicity, let us say that a 



Fig. 2. Comparison microscope using metal- 

 lurgical microscopes, comparison eyepiece and 

 paired Ultrapaks. 



of a similar drill bit mark made in soft sheet 

 metal. While the nature of the mark is dic- 

 tated by the tool used, the over-all identifica- 



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