Recent Developments in Bullet Search Systems

9 Recent Developments in Bullet Search Systems AL JOHNSON

Downloaded by WEIZMANN INST OF SCIENCE on May 26, 2018 | https://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0013.ch009

Ballistics Section, New York City Police Department, New York, N. Y.

Ever s i n c e the i n t r o d u c t i o n of the comparison microscope i n t o the field of advanced firearms i n d e n t i f i c a t i o n i n about 1925, people engaged i n t h i s work have been processing ballistics evidence, b u l l e t s and s h e l l s , i n e x a c t l y the same manner. T h i s can only be done by examining each p i e c e of evidence s e p a r a t e l y and i n d i v i d u a l l y , one p i e c e at a time, and comparing t h i s evidence, again s e p a r a t e l y and i n d i v i d u a l l y , by the utilization of the comparison microscope. Today, we i n the field of f i r e a r m s indentification still process evidence i n e x a c t l y the same manner u s i n g the same techniques and b a s i c a l l y the same instrument that was a p p l i e d almost fifty years ago. "Because t h i s s c i e n c e is very new, it is still i n the throes of vigorous growth. Important c o n t r i b u t a t i o n s to methods and technique are c o n s t a n t l y being made by prominent p r a c t i t i o n e r s such as Luke S. May of S e a t t l e , whose Magnascope may go a long way towards e l i m i n a t i n g the comparison eyepiece, and Captain C.A. Petersen of Miami, F l o r i d a , whose b u l l e t camera has a moving film geared to the b u l l e t stand i n such a way that it takes a s i n g l e p i c t u r e i n the form of a long s t r i p showing all s i d e s of the b u l l e t at once. As time goes on, instruments and methods are bound to be improved at the hands of such men" (1). T h i s paragraph was w r i t t e n over f o r t y years ago. Time has c e r t a i n l y gone by, a great d e a l to time, but instruments and methods are c e r t a i n l y not much improved! In the past fifty years there have been no a p p r e c i a b l e changes in the instruments or methods of examination employed i n t h i s field. Improvements have been made on some of the equipment utilized by firearms examiners. The most obvious change was made by the updating the examiner's major p i e c e of equipment, the comparison microscope. From its e a r l y beginning as an instrument c o n s i s t i n g of a p a i r of compound microscopes mounted s i d e by s i d e on a stand, connected by a s p e c i a l o p t i c a l bridge fitted with a monocular comparison eyepiece, has evolved a h i g h l y s o p h i s t i c a t e d instrument utilizing s p e c i a l mechanical stages and evidence mounting equipment, standard tungsten i l l u m i n a t i o n or the a p p l i c a t i o n 83

Davies; Forensic Science ACS Symposium Series; American Chemical Society: Washington, DC, 1975.


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of c o l d l i g h t sources ( f i b e r o p t i c s ) . B i n o c u l a r eyepieces and turret-mounted o b j e c t i v e l e n s e s supply the t e c h n i c i a n with the o p t i o n of v a r i o u s m a g n i f i c a t i o n s . Other changes i n c l u d e the u t i l i z a t i o n of e l e c t r o n i c measuring devices i n p l a c e of a n a l y t i c a l balances, and v a r i o u s methods of r e c o v e r i n g t e s t specimens have been employed; but no r e a l changes i n the method of examining and evaluating evidence specimens have r e s u l t e d ' During t h i s past year (1973), the New York C i t y P o l i c e Department B a l l i s t i c s S e c t i o n processed 16,184 cases i n v o l v i n g 16,850 i n d i v i d u a l f i r e a r m s . In a d d i t i o n , personnel at t h i s o f f i c e examined and processed evidence i n 750 homicides by gunshot, 71 s u i c i d e s by gunshot and 1772 f e l o n i o u s a s s a u l t s during the commiss i o n of which firearms were used. T h i s work i n v o l v e d thousands and thousands of microscopic comparisons. T h i s c o n s t i t u t e d a 20% increase i n workload over 1972. Evidence recovered i n these cases and t e s t s from the firearms processed by our u n i t had to be compared with an open evidence f i l e numbering more than 25,000 specimens w i t h i n a t e s t specimen f i l e d a t i n g back to the 1930 s. A l l of t h i s comparison work was performed by s i x m i c r o s c o p i s t s , who, i n a d d i t i o n to t h i s work, made frequent court and Grand Jury appearances to t e s t i f y i n these cases, performed s p e c i a l f i e l d i n v e s t i g a t i o n s , and were a v a i l a b l e f o r l e c t u r i n g assignments. Add to these f i g u r e s the number of requests f o r examinations by other p o l i c e agencies across the n a t i o n and the p r o c e s s i n g of t e s t specimens sent i n f o r comparison with evidence c u r r e n t l y on f i l e i n our o f f i c e . The f i g u r e s f o r the f i r s t h a l f of 1974 show a c o n t i n u a t i o n i n the i n c r e a s e i n case l o a d . The s i t u a t i o n i s the same i n f i r e a r m s i d e n t i f i c a t i o n l a b o r a t o r i e s throughout the country. Obviously, a b e t t e r method must be developed f o r the processing of b a l l i s t i c s evidence than the method c u r r e n t l y being used. What i s needed i s some form of automated b a l l i s t i c s f i l e searching system. The computer could c e r t a i n l y be employed as the storage f a c i l i t y f o r such a system. What has yet to be developed i s the apparatus that w i l l take the information that appears on the s u r f a c e of a f i r e d b u l l e t , separate and i d e n t i f y the i n d i v i d ual t o o l marks ( s t r i a t i o n s ) that appear w i t h i n the lands and grooves of a p a r t i c u l a r b u l l e t , transform t h i s i n f o r m a t i o n i n t o a language that w i l l enable the computer to be u t i l i z e d ; that information may be c l a s s i f i e d , f i l e d and s t o r e d , and then s u p p l i e d to the t e c h n i c i a n on demand. We need a system that w i l l a i d i n examining the enormous amount of evidence and t e s t specimens that have accumulated i n our f i l e s , and to perform p r e l i m i n a r y compari s o n work. I t would be too much to expect the development of equipment that would perform p o s i t i v e comparisons f o r us, that i s s e l e c t the one t e s t specimen that compares p o s i t i v e l y with the evidence specimen. We are working to develop equipment that would perform i n the negative aspect of t h i s work, to r e j e c t those t e s t specimens that do not c l o s e l y compare with the evidence at hand, and that would s e l e c t f o r the examiner a c e r t a i n percentage of f



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specimens having s i m i l a r c h a r a c t e r i s t i c s that would have to be compared on the comparison microscope. T h i s automated system should a l s o permit examiners to transmit the information contained i n the r i f l i n g markings on a b u l l e t or the impressions of the breech of a f i r e a r m that appear on the head of a discharged s h e l l to examiners i n other l o c a l i t i e s , r a p i d l y and a c c u r a t e l y , without the worry of p r e s e r v i n g the c o n t i n u i t y of the chain of evidence that becomes our primary concern when t r a n s p o r t i n g evidence and f i r e a r m s . Various proposals have been made along the l i n e s of an automated b u l l e t i d e n t i f i c a t i o n system based on the computer. One of the most promising of the more recent developments was a proposal made i n 1964 f o r a computer-based b a l l i s t i c s i d e n t i f i c a t i o n system u t i l i z i n g a surface analyzer and a small computer. T h i s u n i t c o n s i s t e d of an electro-mechanical scanning component u t i l i z i n g a s t y l u s , one ten-thousandth of an i n c h i n diameter, that contacted the surface of the b u l l e t . The b u l l e t revolved on i t s own a x i s and the s t y l u s recorded the surface i r r e g u l a r i t i e s on the e n t i r e circumference. I t was p o s s i b l e to scan a s i x land b u l l e t i n ten to f i f t e e n minutes, i n c l u d i n g set-up time. The markings picked up by the s t y l u s were magnified by the e l e c t r o n i c u n i t and p r o j e c t e d as l i n e a r graphs or readouts. In concept, t h i s operated i n much the same manner as the s t r i a g r a p h developed around 1951. The s t r i a g r a p h was a mechanical surface analyzer connected to an o p t i c a l device and prisms that d i r e c t e d l i g h t beams onto photo-sensit i v e paper, producing what was then c a l l e d a shadow-graph". Surface-analyzing (or contour-analyzing) methods are a complet e l y d i f f e r e n t approach i n the examination of firearms evidence. They do not d u p l i c a t e or r e p l a c e the comparison microscope. Instead, they give a t r u e r r e p r e s e n t a t i o n of the surface markings on an evidence b u l l e t than the microscope does. The analyzer w i l l chart every surface c h a r a c t e r i s t i c , however minute, and p r o j e c t a r e p r e s e n t a t i o n of that surface onto a l i n e a r , or perhaps c i r c u l a r , graph. The c i r c u l a r graph appears as a c r o s s - s e c t i o n of the b u l l e t . When using the comparison microscope, the examiner observes patterns of shadows created when a l o w - i n t e n s i t y , h i g h l y d i r e c t i o n a l l i g h t source i s d i r e c t e d across an i r r e g u l a r , s l o p i n g , and at times p o o r l y r e f l e c t i v e surface c o n t a i n i n g the minute t o o l marks (or s t r i a e ) and viewed through r e l a t i v e l y low-powered o p t i c s , u s u a l l y l e s s than 2OX m a g n i f i c a t i o n . Surface a n a l y z i n g techniques aim a t being able to reproduce not only s t r i a e , but a l l surface phenomena, i n c l u d i n g r i d g e s and v a l l e y s whose slopes are too gradual to show up under the compari s o n microscope, and to be able to compare not patterns of l i g h t and shade but a c t u a l three-dimensional s u r f a c e s . Other data-gathering techniques have been attempted a t one time or another s i n c e then, such as the photographic r e c o r d i n g of b a l l i s t i c evidence, followed by overlay comparison procedures, or 11



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scanning methods employing photo-detectors. These instruments produced d i g i t a l i z e d v e r s i o n s of the image from c o n t r a s t informat i o n supplied by the photograph. Replica-producing techniques have been employed using v a r i o u s c a s t i n g m a t e r i a l s to produce an accurate, d e t a i l e d reproduction of the evidence specimen. I f the r e p l i c a were of a high q u a l i t y , comparisons could be made u s i n g the r e p l i c a i n place of the a c t u a l specimen. Techniques u t i l i z i n g holographic recordings have been attempted . These holographic recordings are i n the form of photographic records of c e r t a i n l i g h t waves (beams of monochromatic coherent l i g h t separated i n t o i l l u m i n a t i n g and r e f e r e n c e beams) r e f l e c t e d from the evidence, and p r o j e c t i n g three-dimensional images or r e p l i c a s . I t i s p o s s i b l e to make d i r e c t measurements on holographic images of a specimen b u l l e t . The scanning e l e c t r o n microscope (SEM) has been used with some success. During the SEM process, an image i s formed by scanning a f i n e beam of e l e c t r o n s over the sample surface and r e c o r d i n g the secondary e l e c t r o n s i g n a l . Good r e s u l t s have been achieved using t h i s method on f i r i n g - p i n impressions on c a r t r i d g e case heads. However, the a p p l i c a t i o n i s l i m i t e d when examining b u l l e t s . The e n t i r e surface of the b u l l e t cannot be examined without remounting the b u l l e t on i t s stage. The system i s a l s o very slow due to the n e c e s s i t y of c r e a t i n g a vacuum i n the specimen chamber p r i o r to the examination procedure, Recently, the P o l y t e c h n i c I n s t i t u t e of New York C i t y has extended a prop o s a l to the NYCPD to attempt to develop t h i s SEM system more fully. The l a t e s t , and most current proposal f o r an automated b u l l e t i d e n t i f i c a t i o n system has been made by the N a t i o n a l Aeronautics and Space A d m i n i s t r a t i o n . T h i s proposal was o f f e r e d to my department as a f e a s i b i l i t y study i n t o using an o p t i c a l f o u r i e r transform technique f o r c l a s s i f y i n g and comparing the information that appears on the surface of b u l l e t s . In t h i s system, a c o l l i m a t e d coherent l i g h t beam and simple lens system are used to form a f o u r i e r transform from a photographic t r a n s parency of the specimen b u l l e t . T h i s study was approved by the C i t y of New York and i s underway at t h i s time. A l l of the systems p r e v i o u s l y o u t l i n e d w i l l produce a c c e p t a b l e r e s u l t s when d e a l i n g with t e s t specimens. The 'stumbling b l o c k i s the i n a b i l i t y of these systems to cope with the deformi t y of the evidence specimen. The evidence b u l l e t , i n most i n s t a n c e s , w i l l have s u f f e r e d some deformity from the time i t e x i t e d from a gun b a r r e l u n t i l i t f i n a l l y comes to r e s t . I t may be deformed i n any number of ways, f o r example through contact with hard m a t e r i a l s which may m u t i l a t e areas of the surface or perhaps i t may s u f f e r deformity through compression or expansion of the surface area of b u l l e t which would make the b u l l e t land and groove dimensions wider or narrower, compressing or expanding the p a t t e r n of s t r i a e that appear w i t h i n them. As 1



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sometimes happens, evidence b u l l e t s may become so deformed as to make even o p t i c a l comparison impossible. I t i s the b u l l e t that does s u f f e r from some degree of deformity, but s t i l l r e t a i n s enough of i t s surface c h a r a c t e r i s t i c s ( s t r i a t i o n s ) to make p o s i t i v e comparisons p o s s i b l e , that we should be p r i m a r i l y concerned with. The d i f f i c u l t y i s i n the comparison of areas of t e s t b u l l e t s that most times w i l l be i n the form of true c y l i n d e r s , with moderately, o r , at times, s e v e r l y deformed evidence b u l l e t s . Everyone i n v o l v e d with these v a r i o u s proposals r e a l i z e s the urgent need f o r a more modern system than that c u r r e n t l y i n use. The use of the comparison microscope, and the d i r e c t o p t i c a l comparison i n s p l i t - f i e l d observation of each and every separate p i e c e of evidence i s a tremendously time-consuming process. I t a l s o r e q u i r e s the p h y s i c a l presence of a l l evidence and t e s t specimens. The c i r c u l a t i o n of evidence specimens f o r comparison with evidence or t e s t s on f i l e i n other c i t i e s i s a l s o a very c o s t l y and time-consuming process, not to mention the problems that can a r i s e i n maintaining the c o n t i n u i t y i n the chain of possession of evidence. P r e s e n t l y , each comparison r e q u i r e s a manual search through the b a l l i s t i c s evidence f i l e s . T h i s r e q u i r e s time, personnel, and a great d e a l of space devoted to the storage of evidence f i l e s . I t i s my hope that one of these proposals w i l l produce succ e s s f u l r e s u l t s sometime i n the n o t - t o - d i s t a n t f u t u r e , and we i n the f i e l d of firearms i d e n t i f i c a t i o n w i l l reap the b e n e f i t s . Literature Cited 1.

Hatcher, J.S., "Textbook of Firearms I n v e s t i g a t i o n , I d e n t i fication of Evidence", Small Arms P u b l i s h i n g Co., P l a n t e r ville, S.C., 1935, p l 4 .


Recent Developments in Bullet Search Systems

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