1. FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS
Forensic Science - Chapter 16
FIREARMS, TOOL MARKS, AND OTHER IMPRESSIONS

2. Famous People Killed / Wounded with Guns
Abraham Lincoln John Lennon John F. Kennedy Robert F. Kennedy Martin Luther King Jr. Pope John Paul ll Mohandas Ghandi Franz Ferdinand Malcolm X Bob Marley Ronald Reagan Theodore Roosevelt 50 Cent The Notorious B.I.G. Tupac Shakur Sean Taylor

3. How many People Die by Guns?
Guns were used in the USA in 11,422 homicides and 19,392 suicides in 2010, according to the CDC.
In Canada where regular citizens are not allowed to have guns the average is 183 deaths per year.
Interesting Gun Facts: Web site link

4. THE JFK ASSASSINATION
On November 22,1963 the President of the United States, John F. Kennedy was shot and killed on the streets of Dallas. The assassin was identified as Lee Harvey Oswald.
video

5. Faces of the Not Famous Gone due to Guns
Sandy Hook Elementary

6. Columbine Colorado

7. Virginia Tech / Aurora Colorado

8. Introduction
Structural variations and irregularities caused by scratches, nicks, breaks, and wear may permit the criminalist to relate:
A bullet to a gun
A scratch or abrasion mark to a single tool
A tire track to a particular automobile
Individualization, a goal of in all areas of criminalistics, frequently becomes an attainable reality in firearm and tool mark examination.

9. Different Tools / Guns
Tools of all types will leave marks that can be traced back to a source in criminal forensics.

10. Gun Barrel Markings
The inner surface of the barrel of a gun leaves its markings on a bullet passing through it.
These markings are peculiar to each gun.
The gun barrel is produced from a solid bar of steel that has been hollowed out by drilling.
The microscopic drill marks left on the barrel’s inner surface are randomly irregular and serve to impart a uniqueness to each barrel.

11. Father of Ballistics
Calvin Goddard, physician , acquired data from all known gun manufacturers in order to develop a comprehensive database. With his partner, Charles Waite, he catalogued the results of test-firings from every type of handgun made by 12 manufacturers. Waite also invented the comparison microscope. With this instrument, two bullets could be laid adjacent to one another for comparative examination.

12. Ballistic Fingerprinting
Ballistic fingerprinting refers to a set of forensic techniques that rely on marks that firearms leave on bullets to match a bullet to the gun it was fired with.

13. Bullet Recovery Tank
Each gun submitted is test fired and the recovered bullets and cartridge cases are retained for use in further analysis.

14. Recovered Bullets

15. The Bore of Guns

16. Gun Barrel Markings
The manufacture of a barrel also requires impressing its inner surface with spiral grooves, a step known as rifling.
The surfaces of the original bore remaining between the grooves are called lands.
The grooves serve to guide a fired bullet through the barrel, imparting a rapid spin to insure accuracy.

17. Riflings in a Barrell
Riflings are the groves that cause a bullet to spin and gain stability for a more accurate shot

18. Lands and Grooves
Land
Diameter
Caliber
Groove

19. Gun Barrel Markings
The diameter of the gun barrel, measured between opposite lands, is known as caliber. Most older guns’ calibers are measured in fraction of inches across the islands. So a 45 caliber bullet is 0.45 inches across. Some newer bullets are measured in millimeters.
Once a manufacturer chooses a rifling process, the class characteristics of the weapon’s barrel will remain consistent, each will have the same number of lands and grooves, with the same approximate width and direction of twist.

20. Striations
Striations, which are fine lines found in the interior of the barrel, are impressed into the metal as the negatives of minute imperfections found on the rifling cutter’s surface, or they are produced by minute chips of steel pushed against the barrel’s inner surface by a moving broach cutter.
These striations form the individual characteristics of the barrel.

21. Bullet Striations from the Barrel
The striations on the bullet can make identifiable and unique markings that trace it back to a particular firearm.

22. Striations
It is the inner surface of the barrel of a gun that leaves its striation markings on a bullet passing through it.
Courtesy of C. Fanning

23. Bullet Examination
No two rifled barrels, even those manufactured in succession, will have identical striation markings.
The number of lands and grooves and their direction of twist are obvious points of comparison during the initial stages of an examination between an evidence bullet and a test-fired bullet.
Any differences in these class characteristics immediately serve to eliminate the possibility that both bullets traveled through the same barrel.

24. The Comparison Microscope
The comparison microscope serves as the single most important tool to a firearms examiner.
Two bullets can be observed and compared simultaneously within the same field of view.
Not only must the lands and grooves of the test and evidence bullet have identical widths, but the longitudinal striations on each must coincide.

25. Comparison of Bullet Marks

26. Bullets become scarred by rifling as they travel down the barrel of a gun

27. Matching Procedure Fire bullets from a suspected weapon
With the aid of a comparison microscope, compare these “test fires” to the suspected bullets
Striations must be identical for a positive match

28. Comparison Microscope
Two scopes- One Field

30. Handguns Semi-automatic
Courtesy of C. Fanning
Courtesy of C. Fanning
Courtesy of C. Fanning

31. Parts of a Semi-auto Handgun

32. Parts of a Semi-auto Pistol

33. 9 mm Glock

34. 25 Auto Bauer
Saturday Night Special
Semi-automatic
Capacity: 10 rounds

35. Parts of a Handgun

36. Handguns Revolver

37. 6 rounds 38 Special with a speed loader

38. 38 Taurus Ultra-lite
6 Rounds

39. 22 Ruger-Old Western Style
Single Action

40. Muzzleloading Rifle

41. Parts of a Bolt Action Rifle

42. Lever Action Rifle
A lever action rifle is one that reloads with the use of a rotating lever handle.

43. Parts of a Semiautomatic Rifle
M1 carbine will fire each time you pull the trigger without manually reloading. The shells are held in the vertical clip under the receiver.

44. Modern Smart Guns
The newest rifles have the same computerized targeting systems as military fighter aircraft. Cost: $27k They can shoot targets 10 football fields away. Video

45. Automatic Assault Rifles
The most deadly gun that is commonly hand carried by the shooter. It can fire many rounds without reloading; as fast as you can pull the trigger and can be set to fully automatic mode.

46. Machine Guns
Fully automatic machine guns can fire up to 1200 bullets per minute.
50 Cal video

47. Rapid Fire Machine Gun
Typical cyclic rates of fire are 500–900 RPM for assault rifles, 900-1,200 RPM for submachine guns and machine pistols, and 600-1,200 RPM for machine guns. M134

48. SHOTGUNS Unlike rifled firearms, a shotgun has a smooth barrel.
Shotguns generally fire small lead balls or pellets that are not impressed with any characteristic markings that can be related back to the weapon.

49. Shotguns
The diameter of the shotgun barrel is expressed by the term gauge. In the lower numbered gauges, it is the number of pellets that are needed to span the internal barrel diameter.
The higher the gauge number, the smaller the barrel’s diameter.

50. Shotgun & Shells

51. Shotgun Impact Patterns
The firing distances involving shotguns must again be related to test firing.
The muzzle to target distances can be established by measuring the spread of the discharged shot.
Full choke goes out to about 50 yards, modified out to about 35 yards, Imp Cylinder about 20 yards, sawed-off about 10 yards.

52. Reloading Shotguns Manual pump ejection out the side of the receiver
Breechloading

53. Firing a Weapon
The act of pulling the trigger serves to release the weapon’s firing pin, causing it to strike the primer, which in turn ignites the powder.
The expanding gases generated by the burning gunpowder propel the bullet forward through the barrel, simultaneously pushing the spent cartridge case or shell back with equal force against the breechblock.

54. Firing a Weapon
The shell is impressed with markings by its contact with the metal surfaces of the weapon’s firing and loading mechanisms.

55. Ammunition

56. Calibers of Bullets

57. Caliber of Gun Bores

58. Ammunition
Components:
Cartridge case
Primer
Propellant
Projectile

59. Cartridge Case Usually brass or nickel-clad brass Head stamps
Rimfire and centerfire cartridges
Class evidence

60. Cartridge Case, continued
Individual characteristics
Firing pin marks
Extractor marks
Breech marks

64. Bullet Design
“Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired
Bullets vary in shape and composition
There exist hundreds of different types of bullets
Most types are variations on three main shapes & three basic compositions

65. Three Main Shapes

66. Round Nose
Maximum penetration
Cheapest shape to manufacture
Easily loads into chambers

67. Hollow Point Spreads or mushrooms on impact
Causes additional damage to target
Inhibits penetration

68. Wad Cutter Used exclusively as a practice load Minimizes penetration
Rips a hole in target paper which is visible by the shooter

69. Three Basic Compositions of Bullets
Lead
½ Jacketed
Jacketed (Full metal jacket)

70. Lead
Cheap
Dense
Soft
Easy to mold

71. ½ Jacketed
A lead bullet coated with copper half way up the exposed portion of the bullet
Used primarily for
hollow points
Copper improves
exit velocity
Lead promotes mushrooming

72. Jacketed A lead bullet completely coated in copper
Copper improves exit velocity and accuracy of the trajectory.
Used to hold the shape of the bullet in an effort to maximize penetration

73. Distance to Target
The Greiss test converts nitrites to an orange-red color.
Sodium rhodizonate reacts with traces of lead to make purple spots.

75. Shotgun injuries

77. Cartridge Case Comparison
The firing pin, breechblock, and ejector and extractor mechanism also offer a highly distinctive signature for individualization of cartridge cases.
Courtesy of C. Fanning

78. Cartridge Case Comparison
The shape of the firing pin will be impressed into the relatively soft metal of the primer on the cartridge case.
The cartridge case, in its rearward thrust, is impressed with the surface markings of the breechblock.

79. Cartridge Case Comparison
Other distinctive markings that may appear on the shell as a result of metal to metal contact are caused by the:
Ejector, which is the mechanism in a firearm that throws the cartridge or fired case from the firearm.
Extractor, which is the mechanism in a firearm by which a cartridge of a fired case is withdrawn from the firing chamber.
Magazine or clip, which is the mechanism that in a firearm holds the bullets.

80. Computerized Imaging for Ammo
The advent of computerized imaging technology has made possible the storage of bullet and cartridge surface characteristics in a manner analogous to automated fingerprint files.

81. Computerized Imaging
IBIS ( Integrated Ballistic ID System) by the ATF was the original database until 1999.
The National Integrated Ballistics Information Network, NIBIN, produces database files from bullets and cartridge casings retrieved from crime scenes or test fires from retrieved firearms, often linking a specific weapon to multiple crimes. Took place of IBIS.
It is important to remember, however, that the ultimate decision for making a final comparison will be determined by the forensic examiner through traditional microscopic methods.

82. NIBIN

83. Gunpowder Residue
When a firearm is discharged, unburned and partially burned particles of gunpowder in addition to smoke are propelled out of the barrel along with the bullet toward the target.
If the muzzle of the weapon is sufficiently close, these products will be deposited onto the target.
The distribution of gunpowder particles and other discharge residues around a bullet hole permits an assessment of the distance from which a handgun or rifle was fired.

84. Gunpowder Residue
The precise distance from which a handgun or rifle has been fired must be determined by means of a careful comparison of the powder-residue pattern located on the victim’s clothing or skin against test patterns made when the suspect weapon is fired at varying distances from a target.
By comparing the test and evidence patterns, the examiner may find enough similarity in shape and density upon which to base an opinion as to the distance from which the shot was fired.
Infrared photography can sometimes show better contrast with the burned powder and the cloth of a victim. Scanning Electron Microscopy and X-ray spectroscopy can identify the residue from a swab of the hands or wound.

85. Gunpowder Residue Detection

86. Gunpowder Residue
In cases where the weapon is held in contact with or less than 1 inch from the target, a star-shaped (stellate) tear pattern around the bullet hole entrance, surrounded by a rim of a smokeless deposit of vaporous lead is usually present.
A halo of vaporous lead (smoke) deposited around a bullet hole is normally indicative of a discharge of 12 to 18 inches or less. This deposits on the hands of a shooter and can be chemically analyzed for proof of shooting a gun.

87. Gun Powder Residue around Wounds

88. Gunpowder Residue
The presence of scattered specks of unburned and partially burned powder grains without any accompanying soot is often observed at distances up to 25 inches (and occasionally as far as 36 inches).
More than 3 feet, will usually not deposit any powder residues, and the only visual indication is a dark ring around the hole, known as a bullet wipe.

89. Gunpowder Residue
When garments or other evidence relevant to a shooting are received in the crime laboratory, the surfaces of all items are first examined microscopically for the presence of gunpowder residue.
Chemical tests, such as the Greiss test, may be needed to detect gunpowder residues that are not visible. Atomic Absorption spectroscopy is also used to prove the presence of gun powder residue. Time is important for analyzing GSR before normal usage wipes off the nitrates.

90. Griess Test
The Griess test is a chemical analysis test which detects the presence of organic nitrite compounds. The Griess diazotization reaction on which the Griess reagent relies was first described in 1858 by Peter Griess.

91. Powder Residue on Clothing

92. Primer Residue on Hands
The firing of a weapon not only propels residues toward the target, but gunpowder and primer residues are also blown back toward the shooter.
As a result, traces of these residues are often deposited on the firing hand of the shooter, and their detection can provide valuable information as to whether or not an individual has recently fired a weapon.

93. Primer Residue on Hands
Examiners measure the amount of barium and antimony on the relevant portion of the suspect’s hands, such as the thumb web, the back of the hand, and the palm.

94. Primer Residue on Hands
They may also characterize the morphology of particles containing these elements to determine whether or not a person has fired, handled a weapon, or was near a discharged firearm.

95. Serial Numbers
Serial numbers are used to trace the ownership of a gun to a suspect or source. Increasingly, the criminalist is requested to restore a serial number when it has been removed or obliterated by grinding, rifling, or punching.
Restoration of serial numbers is possible through chemical etching because the metal crystals in the stamped zone are placed under a permanent strain that extends a short distance beneath the original numbers.

96. Serial Numbers on Guns

97. Firearm Evidence Collection
Firearms are collected by holding the weapon by the edge of the trigger guard or by the checkered portions of the grip.
Before the weapon is sent to the laboratory, all precautions must be taken to prevent accidental discharge of a loaded weapon.
In most cases, it will be necessary to unload the weapon.

98. Firearm Evidence Collection
When a revolver is recovered, the chambers, their positions, and corresponding cartridges must be recorded.
Firearm evidence must be marked for identification (usually a tag on the trigger guard) and a chain of custody must be established.

99. Firearm Evidence Collection
Bullets recovered at the crime scene are scribed with the investigator’s initials, either on the base or the nose of the bullet.
The obliteration of striation markings that may be present on the bullet must be scrupulously avoided.
The investigator must protect the bullet by wrapping it in tissue paper before placing it in a pillbox or an envelope for shipment to the crime laboratory.

100. Firearm Evidence Collection
Fired casings must be identified by the investigator’s initials placed near the outside or inside mouth of the shell.
Discharged shotgun shells are initialed on the paper or plastic tube remaining on the shell or on the metal nearest the mouth of the shell.

101. Tool Marks
A tool mark is considered to be any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object.
A careful examination of the impression can reveal important class characteristics, such as the size and shape of the tool.

102. Tool Marks
But it is the presence of any minute imperfections on a tool that imparts individuality to that tool.
The shape and pattern of such imperfections are further modified by damage and wear during the life of the tool.

103. Tool Marks
The comparison microscope is used to compare crime-scene toolmarks with test impressions made with the suspect tool.
When practical, the entire object or the part of the object bearing the tool mark should be submitted to the crime laboratory for examination.

104. Tool Marks
Under no circumstances must the crime scene investigator attempt to fit the suspect tool into the tool mark.
Any contact between the tool and the marked surface may alter the mark and will, at the least, raise serious questions about the integrity of the evidence.

105. Tool marks on bones
Tool marks on bones can identify the type of tool that was used in the crime and may isolate it down to individual evidence for a trial.

106. Other Impressions
Impressions of other kinds, such as shoe, tire or fabric impressions, may be important evidence.
Before any impression is moved or otherwise handled, it must be photographed (including a scale) to show all the observable details of the impression.
If the impression is on a readily recoverable item, such as glass, paper, or floor tile, the evidence is transported intact to the laboratory.

107. Footprints and Tire Marks

108. Other Impressions
If the surface cannot be submitted to the laboratory, the investigator may be able to preserve the print in a manner similar to lifting a fingerprint.

109. Other Impressions
When shoe and tire marks are impressed into soft earth at a crime scene, their preservation is best accomplished by photography and casting.
In areas where a bloody footwear impression is very faint or where the subject has tracked through blood leaving a trail of bloody impressions, chemical enhancement can visualize latent or nearly invisible blood impressions.

110. Points of Comparison
A sufficient number of points of comparison or the uniqueness of such points will support a finding that both the questioned and test impressions originated from one and only one source.
New computer software and web sites may be able to assist in making shoe print and tire impression comparisons.
Also, bite mark impressions on skin and foodstuffs have proven to be important evidence in a number of homicide and rape cases.

111. Tools often used in burglaries may leave a mark.
Toolmarks
Tools often used in burglaries may leave a mark.
Class characteristics: type, size, shape
Individual characteristics: features from wear and damage

112. Matching Toolmarks ? ?
Photography and casting are important to match tool with mark.

113. Ick.

115. Impressions Class characteristics— manufacturer, type, model, size
Shoeprints
Class characteristics— manufacturer, type, model, size
Individual characteristics— wear patterns, nicks, marks, occlusions (like pebbles or sticks)

116. Impressions, continued
Shoeprints
Captured by oblique-angle photography or chemical enhancement; also by casting in soil, or lifting.

117. Footprint

118. Impressions, continued
Treated much the same as shoeprints
Tire Treads
Class characteristics involve design, size, type, and model.
Wear and damage cause defects that can lead to individualization.

119. Impressions, continued
Tire Treads
TreadMate is a database containing data on more than 5,000 vehicle tires and tread patterns.

120. Tire Treads

121. Impressions, continued
Bite Marks
Result from assault or sexual attack, common in domestic violence
Individual evidence, if enough impressions
Bite marks were the prime evidence in the conviction of serial killer Ted Bundy.

122. Bite mark

123. Bitemarks and Computer Analysis

124. Where is this bite mark located?

125. Most famous bite mark case of the 20th century

126. Comparison of Bundy’s teeth
Wax impression
From victim

127. Impressions, continued
Serial Numbers
Restoration of serial numbers
Items of value may have ID numbers stamped into them.
Grinding is usually used to obliterate identification numbers.
To restore ID numbers on metal, an acid etching solution is employed.
HCl-CuCl2