Positive identifications of firearms that have led to the solution of major crimes have been made in cases where no suspect gun was found. In some instances fired cartridges, either known to have been fired by the suspect on a previous occasion in a gun which belonged to him or found in the possession of a suspect, have been instrumental in solving the case. In other cases a bullet known to have been fired by the suspect from a firearm known to have belonged to him (or to have been in his possession) furnished the necessary evidence. One of these cases is interesting because of its international character. In a murder case which occurred several years ago in Saskatchewan this procedure was used. A former U.S. citizen from Kentucky had moved to Canada to make his home there and became a suspect in a murder case in which no gun could be found. Diligent inquiry in the locality of his former home in Kentucky disclosed that he had owned a rifle of the same caliber as that used in the commission of the murder. An extensive search of the area where he was known to have fired this gun in target practice before moving to Canada revealed bullets that he had fired. When these were compared with the evidence bullet in Canada they were found to match, and he was convicted of the murder. Determination o f the manufacturer o f ammunition
The manufacturers of cartridges usually identify their product by a mark placed on the head of the cartridge, and these „head stamps," as they are called, serve to identify the maker of the fired shell case. Since there are many manufacturers there are necessarily a great number and variety of head stamps. A well-equipped firearms identification laboratory should have as large a collection as possible of cartridges and cartridge components for identification purposes. Such extensive collections require much time, patience, and expense in collecting. However, there are compilations of reproductions of head stamps and these are of great value in making identifications.
The determination of the manufacturer of a particular fired bullet is not so easy, particularly if it is of foreign make. The practice of putting an identifying letter on the bullet, formerly quite extensively used, has almost disappeared. Bullets of current U.S. manufacture are not so marked.
The type, shape, and number of serrations in the cannelures are sometimes a clue to the manufacturer. The cannelures are made by knurling them into the formed bullet, or they may be formed as the bullet is swaged. Since different manufacturers use different forms of knurls or swages the cannelures will often be quite distinctive. Known samples in the laboratory „ammunition component parts file" frequently lead to the desired answer. Specifications for cannelures furnished by the manufacturer should not be relied on, as they often do not represent actual production procedures and, therefore, may be misleading. Fortunately, the question of who made the bullet is of little if any importance, but it is important to use bullets of similar size, weight, and dimensions in getting test bullets for comparison purposes. The problem as to whether two bullets came from the same source and, particularly, out of the same lot of ammunition is an easier one to solve. Formerly, resort was made to chemical analysis and determination of densities, both very time-consuming and tricky operations requiring a considerable degree of skill. Also, a significant amount of the metal of the bullet would be lost because of the size of the sample required for the chemical analysis. These methods need no longer be used since analysis by means of the spectrograph has become so common. Every modern crime laboratory has one of these instruments, but should a police laboratory not have one there are many commercial laboratories who can furnish the service required. A spectrographic test can be made by an expert in a few minutes. The determination of each and every metallic element present is made both qualitatively and quantitatively, and the amount of the specimen required for the analysis is almost microscopic in size, thus no significant amount of the evidence is destroyed.
If the spectrograms of the evidence bullet and a bullet found in the defendant's possession are identical, qualitatively and quantitatively, it is very good evidence that the two bullets not only came from the same manufacturer but in all probability came from the same batch of metal! Conversely, if the spectrograms are unlike, it is positive proof that the bullets did not come from the same batch of metal. Of course, they could have been made by the same manufacturer but at different times. The manufacturer may get his lead from different sources and, consequently, there will be significant differences (as determined spectrographically) in the bullets he makes. Likewise, different manufacturers may get their lead from different sources, and spectrographic differences will show up in their products.
Fig. 19. Matching of rim fire firing pin impressions. Occasionally the impressions made by a firing pin on a rim fire shell are sufficiently well defined and so repetitive as to permit matching them with the comparison microscope or the comparison camera. Two such matchings are shown.
Three shells (A, B, & C) were fired in the same Remington rifle. The left photo shows Shell A (top) matched with Shell B. At the right is shown the matching of Shell C (top) with Shell A. The photos were made with the comparison camera.
Fig. 20. Matching of rim fire firing pin marks (comparison microscope photo). Matchings of this quality are rarely found on .22 cal. rim fire shells. Inasmuch as they are conclusive evidence a search for matchings should always be made.
Fig. 21. Illustrating variation in point of impact of firing pin. (See text for discussion.)
Fig. 22. Semicircular firing pin impressions. The impression on this shell, fired in an Iver Johnson D.A. Model 1900 revolver, would be classed as „Semicircular." However, the impression of the firing pin made on a thin sheet of copper (shown at the left) shows that the pin actually has a rectangular striking surface, rounded at the lower end. Since only this lower portion of the pin strikes the rim of the shell a semicircular effect is produced. Such vagaries are frequently encountered.
Fig. 23. Semicircular firing pin impressions. The two shells were fired in an Iver Johnson „Supershot Sealed Eight" revolver. Impressions made by the same firing pin on a piece of sheet copper are shown below and demonstrate that the end of the pin is circular and flat. Most semicircular impressions are caused by the end of a round pin striking on the edge of the rim of the shell, as was the case here illustrated.
Fig. 24. Matching of breechblock marks (comparison microscope photos). All four of these matches were obtained on the same pair of shells. Test shell above line of separation in each case.
Fig. 25. Matching of breechblock markings (comparison microscope photo). Showing two matchings obtained on fatal shell (below line) and test shell (above line) fired in Sauer Auto Pistol belonging to suspect. See Fig. 41 for photo of breechblock in this gun.
Fig. 26. Shell heads in Sacco-Vanzetti case. Left: Test shell from Sacco's automatic. Right: Evidence shell.
Comparison microscope was not used in the investigations. Similarities in the breechblock markings are obvious, however.
Fig. 27. A rather unusual number of markings found on each primer of shells fired in this gun.
Fig. 28. Breechblock markings. Left: Test shell fired from suspect's gun. Right: Fatal shell found at murder scene.
Fig. 29. Primers on evidence shell (left) and test shell (right) show same Breechblock marks and same firing pin drag. All test shells fired showed this.
Fig. 30. Matching of breechblock0 markings on rim fire shells. Above: Two shells fired in a Springfield Rifle, Model 4. Below: Comparison microscope photo showing good matching of breechblock markings.
Fig. 31. Matching extractor marks (Rifle). Above line: Mark on test shell. Below line: Mark on fatal shell.
Fig. 32. Matching extractor marks (Pistol). Above line: Mark on test shell. Below line: Mark on fatal shell.
Fig. 33. Matching extractor marks (Shotgun). Above line: Mark on test shell. Below line: Mark on fatal shell.
Fig. 34. Matching of extractor marks (Shotgun). Left: Above line, extractor mark on fatal shell. Below line, mark made by left hand extractor on test shell. Right: Above line, extractor mark on fatal shell. Below line, mark made by right hand extractor on test shell.
Fig. 35. Matching of extractor marks. (An unusual case.) A .30-30 cartridge was fired in a .32 caliber Marlin Mod. 1893 repeating rifle in a murder case. As would be expected, matching of the fatal bullet with test bullets (of either caliber) could not be obtained. Distinctive breechblock markings were absent. But on the fatal shell there was an excellent extractor mark which could be matched with those produced on test shells.
Fig. 36. Matching extractor marks refute statement that suspect did not own rifle. Above line: Mark on a cartridge taken from suspect. Below line: Mark on evidence shell.
Evidence shell and test shells fired from a Winchester Mod. 94 .32 Spl. rifle showed matching extractor marks, but suspect denied ownership or knowedge of the rifle. Inadvertently he dropped two unfired cartridges while being interviewed. Each of these unfired cartridges had obviously been „worked through" the rifle since each of them had extractor marks on their rims which matched those on the evidence shell, thus refuting the suspect's statement. (Photo by courtesy of Wisconsin State Crime Lab.)
Fig. 37. Matching of ejector marks (Shotgun). Above line in all three photos: Ejector mark on fatal shell. Below line: Ejector marks made on three different test shells fired in this gun.
Fig. 38. Matching of loading marks. Comparison microscope photograph showing matching of loading mark on a test shell (above line) with similar mark on evidence shell (below line). Caused by a defect in the loading mechanism of the rifle.
Fig. 39. Scrape marks on primer. Left: Scrape mark on primer of shell fired in a .45 cal. Colt automatic pistol. Right: Two scrape marks made by same pistol matched under comparison microscope.
Fig. 40. An unusual case of „firing pin drag," caused by unlocking of the tip-up barrel of a shotgun at moment of explosion.
Fig. 41. Left: Shell head fired in Sauer Auto Pistol showing cone-shaped mark on primer. Right: Breechblock in Sauer Auto Pistol showing cause of mark.
Fig. 42. Marks made by shell striking slide. In the ejection of shells from some makes of automatic pistols the shell often (if not invariably) strikes the edge of the port in the slide and a distinctive mark often results. In some cases these can be matched, in others they cannot. These two photos show marks produced on shells fired in a 7.65 mm. Dreyse. The marks are about half way up the side of the shell directly below the extractor marks and have the appearance of small gashes. Left hand shell is the evidence shell, test shell is at the right. Similar marks were found on all test shells fired. The extractor marks matched very well, positively identifying the murder gun.
Fig. 43. Enlargement of marks shown in Fig. 42. The photo at the left shows the two gash marks greatly magnified. Mark on evidence shell at the left, test at the right.
The photo at the right shows the two brought together under the comparison microscope in an attempt to get a matching of the marks. The results were not satisfactory, only a general resemblance being shown.
Fig. 44. Identification by markings produced on the side of a fired shell. While this situation seldom occurs, and therefore the procedure is rarely used, such markings may be very useful in making an identification. Above line: Mark produced on body of a test shell fired in a Czech M-27 pistol. Below line: Mark found on evidence shell. (Courtesy of Wisconsin State Crime Lab.)
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