Presentation on theme: "Syracuse University June, 2010"— Presentation transcript:
1Syracuse University June, 2010 Firearms and Toolmarks
2Forensic Firearm Analysis WALLIE HOWARD JR.CENTER FOR FORENSIC SCIENCESMatthew KurimskyFirearms Examiner
3FORENSIC FIREARMS IDENTIFICATION A scientific process of determining whether a bullet or cartridge case was fired from a particular weapon. This is done by examining and evaluating the class and individual characteristics imparted onto the bullet or cartridge case.
4FIREARMS SECTION FIREARM IDENTIFICATION OPERABILITY ANALYSIS FIREARM COMPARISONSPHYSICAL MATCH COMPARISONSIBIS ENTRIESSERIAL NUMBER RESTORATIONGUNSHOT RESIDUE DISTANCE DETERMINATION
5FIREARMS IDENTIFICATION Can determine the general condition of a firearm and whether the firearm is mechanically functional.Can determine whether the firearm was altered to fire in full-automatic mode.Can be test fired to obtain known specimens for comparison to evidence ammunition components.
8CLASS CHARACTERISTICS Are measurable features of a specimen that indicate a restricted group source.Result from design factors, and are determined prior to manufacture.Examples are firing pin shape, caliber, and general rifling characteristics.
13COMMON TYPES OF RIFLING BROACH RIFLING:Cuts the grooves by being pushed or pulled through the barrel while being rotated.BUTTON RIFLING: Pushed or pulled through a drilled and reamed barrel so as to cold form the spiral grooves to the desired depth and twist. NOT a cutting process.
14GENERAL RIFLING CHARACTERISTICS The number, width and direction of twist of the rifling grooves in a barrel of a given caliber firearm.
15INDIVIDUAL CHARACTERISTICS Marks produced by the random imperfections or irregularities of tool surfaces.These random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion, or damage.They are unique to that tool and distinguish it from all other tools.
16COMPARISON MICROSCOPE Optically bridged so objects can be viewed side by side.
17CARTRIDGE CASE OR SHOTSHELL EXAMINATION Cartridge case examination can determine the caliber or gauge, and the manufacturer.The images of questioned cartridge cases can be entered into IBIS to compare with evidence from other shooting incidents.The microscopic characteristics of evidence cartridge cases can be examined to determine whether they were fired in a specific firearm.
18CARTRIDGE CASING IDENTIFICATION Parallel breech face marks.
19Circular breech face marks. Granular breech face marks.
22BULLET EXAMINATIONSBullets can be examined to determine the general rifling characteristics.The microscopic characteristics on evidence bullets can be compared to test-fired bullets from a suspect firearm to determine whether the evidence bullet was fired from that firearm.
24Bullet comparisonsThe gun barrel is produced from a solid bar of steel that has been hollowed out by drillingThe microscopic drill marks left on the barrel inner surface are randomly irregular and would in themselves serve to impart a uniqueness to each barrel.Manufacturers make the inner surface of the barrel with spiral groves, a step known as rifling
25Bullet comparisons Why rifling in a barrel? Prevents the bullet from tumbling when it leaves the barrel, more accuracy.
26Bullet comparisonsThe diameter of the gun barrel is measured between opposite lands, this is known as the caliber of the weapon. It is usually expressed in hundredths of an inch (.22) or millimeters (9mm)Caliber - the diameter of the bore of a rifled firearm.
27Bullet comparisonsEvery firearms manufacturer chooses a rifling process that is best suited to meet the production standards and requirements of its product.Once the choice is made, the class characteristics of the weapons barrel will remain consistent; each will have the same number of lands and grooves, the same approximate width and directions of twist.
28Bullet comparisons Ex: .32 caliber Smith & Wesson revolvers have five lands and grooves twisting to the rightEx:.32 caliber Colt revolvers exhibit six lands and grooves twisting to the left
29Bullet comparisonsThere are fine lines or striations, many running the length of the barrel’s lands and grooves.These are caused by 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.The fact is that the random distribution and irregularities of these markings are impossible to duplicate exactly in any two barrels.
30Bullet comparisonsNo two rifled barrels, even those manufactured in succession, will have identical striation markings!These striations form the individual characteristics of the barrel.The number of lands and grooves, and their direction of twist are obvious points of comparison during initial stages of the examination
31Bullet comparisonsBy comparing the lands and grooves and directions of twist, we can eliminate certain weapons.The most important tool for the firearms examiner is the comparison microscope.
36Bullet comparisons With shotguns, most barrels are smooth The diameter of the shotgun barrel is expressed by the term gaugeGauge - the number of lead balls with the same diameter as the barrel that would make a poundex: 20 ga = diameter of lead ball weighing1/20th of a poundException to this is 410 gauge, actually is .410 inch diameter
37PHYSICAL MATCH COMPARISON Physical match comparison can determine whether evidence was joined together and subsequently broken apart.
40INTEGRATED BALLISTICS IDENTIFICATION SYSTEM (IBIS) Images of projectiles and cartridge casings recovered from the crime scene, or produced from evidence weapons are entered into the database and searched.Used to link multiple crimes to a single weapon.
41Potential hits are compared to one another by a firearms examiner on a comparison microscope. Hits are NOT made by simply looking at the images in IBIS.
42SHOT PELLETS, BUCK SHOT, OR SLUGS Examination of shot pellets, buck shot, or slugs can determine the size of the shot or the gauge of the slug, and the manufacturer.
45WADDING EXAMINATIONSExaminations of wadding components can determine the gauge and the manufacturer.
46UNFIRED CARTRIDGES OR SHOTSHELLS Examinations of unfired cartridges or shotshells can determine the caliber or gauge and whether there are marks of value for comparison.Examinations can also determine whether the ammunition was loaded into and extracted from a specific firearm.Unfired and fired cartridges or shotshells can be associated through manufacturing marks.
47SERIAL NUMBER RESTORATIONS Obliterated and/or altered firearm serial numbers can sometimes be restored.Chemical, electrolytic, and magnetic particle inspection are some of the methods used.
53Gunpowder residuesThe accuracy of a distance determination varies according to the circumstances of the caseBecause the spread and density of the residue pattern will vary widely between weapons and ammunition.
54Gunpowder residuesA COMPARISON IS SIGNIFICANT ONLY WHEN IT IS MADE WITH THE SUSPECT WEAPON AND AMMUNITION OR AMMUNITION OF THE SAME MAKE AND TYPE
56Gunpowder residuesItems that influence estimating target distance (amt. Of gunpowder residue)Barrel lengthCalibertype of ammunitionType and condition of the weapon fired
57Gunpowder residues Tests done on garments in the lab Examine microscopically for presenceof gunpowder residueNitrite test - greis testSodium rhodizoante test (lead)Greis test - a chemical test to develop patterns ofgun powder residues around bullet holes
64During the firing process. GSRDuring the firing process.GSR particle.
65CLASS CHARACTERISTICS ToolmarksDefined as any impression, cut, gouge, or abrasioncaused by a tool coming into contact with anotherobjectUSUALLY THERE WILL BECLASS CHARACTERISTICSSIZESHAPE
66Sometimes nicks and wear patterns will individualize a tool ToolmarksSometimes nicks and wear patterns will individualize a toolINDIVIDUAL CHARACTERISTICS ARE HARD TO IDENTIFY BECAUSE OF THE DIFFICULTY OF DUPLICATING THE TOOL MARK IN THE LAB