3 Inside the Oakland Crime lab- ballisticsBritain’s CSI School- ballistics
4 JFK Assasination (3 min in- also power point- lindbeck Cold case JFK Nova
5 Bullet Comparison Firearms Identification: people identify whether a bullet/cartridge was fired by a weaponIdentifier has knowledge of types of weapons, serial # restoration, gunpowder detection, distance determinationFirearms Identification System (IBIS)Ballistic Identification system (same)
7 Grooves: Rifling: Bore: Cuts or low lying portions between lands in the barrel of the gunRifling:Spiral grooves that are formed in the bore of the barrel to impact a spin to the projectileBore:Interior of fire arm barrel
8 Lands: Caliber: The raised portion between grooves Diameter of the bore (distance between opposite lands) measured in 100th of an inch or mm (Typical: .22,.32,.38,.45 or 9mm)
10 Rifling ProcessBroach cutter (series of concentric rings, each bigger than the next)button process(steel plug w/ grooves forced through barrel, no cutting)mandrel rifling (rod of steel is inserved into oversized barrel which is compressed)
11 No two rifled barrels, even those manufactured in succession, will have identical striation markings Riflings (pitch and twist), lands and caliber are class characteristics while striations are individual to a barrel. These characteristics are impressed onto bulletsExamine test and evidence bullets w/ a comparison microscope
12 ShotgunsMost have smooth barrels w/ diameter in gauge (Note: can have rifled shotgun barrels)Higher the gauge the smaller the diameter
13 Note: FBI maintains General Rifling Characteristics File ( data on known weapons)
14 Cartridge Cases Breechblock: rear part of firearm barrel Extractor: mechanism in a firearm by which a cartridge of a fired case is withdrawn from the chamberEjector: mechanism in a firearm that throws the cartridge or fired case from the firearm
15 The act of pulling a 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 with equal force against the breechblock. The shell is impressed with markings by its contact with the metal surfaces of the weapons firing and loading mechanisms
17 BreechblockThe breechblock has striations from the machining process that individualize its surface
18 Breech face marksThe cartridge head is seated against the breechblock of the weapon.When the bullet is fired, the cartridge case is shoved back into the breechblock with the same amount of force. This imprints the striations of the breechblock onto the cartridge casing.
19 Ejector MarksImparted to the cartridge case when it is ejected out of the weapon.
20 Extractor marksImparted onto the cartridge case when the case is extracted from the barrel.
21 Cartridge case is impressed w/ markings by contact w/ the firing pins and loading mechanism (individual char.)Firing PinBreechblock
22 Firing pin, breechblock, extractor and ejector marks may also be impressed onto shotgun shells Cases give distinctive points of comparison for individualization (get random striations markings, imperfections, surface markings)
23 Bullet Characteristics ClassNumber, width,depth of lands and grooves (on a bullet the lands will be an indentation the grooves a raised portion)twistIndividualStriae impressed by barrelStriae due to wear and useStriae due to neglect and abuse
24 Cartridge Case Characteristics ClassTrademarks (manufacturer’s name, head stamp)Shape (rimmed, rimless, straight)CalibercompositionIndividualFiring pin impressionsBreech face marksEjector marksExtractor marks
25 Forensic Chemistry Lab (starts with striations, ends with serial id)
26 Automated Firearm Search Systems Allows FBI to store bullet and cartridge surface characteristicsAllows a network of jurisdictions to share info
27 IBIS: Integrated Ballistic ID system DRUGFIRE: FBI system emphasizing unique markings on cases (esp. guns w/ gang or drug background)IBIS: Integrated Ballistic ID systemDigital microscopic images of identifying features on expended bullets & cartridge casesSoftware used: Bulletproof & Brasscatcher
29 Gunpowder residueFiring distances are approximated by the study of spread and density of gunshot residue (GSR)Chemicals Left Behind:Unburned & partially burned particles of gunpowder and smoke (get deposited on hands, clothes)Vaporous leadAmmunition is a blend of lead, BaNO3, antimony sulfide
40 Studying Gunpowder on Clothing Examine microscopicallyIf lack of color contrast or blood is present – use infrared photographyChemical Test (for nitrates)Gneiss- develops patternSodium Rhodizonate w/ acidGSR
46 Serial Number Restoration Serial #’s are found on engine blocks, firearms, other manufactured itemsCriminalist is called in when # is obliteratedStamping of serial # causes a permanent strain which extends into the metal surface (beneath the original #’s)Chemical treatment w/ etching agents makes obliterated #’s appearEtching agents dissolve faster in strained areas-but if obliteration is below zone of strain-NO HELP
48 Trajectory Two reference points are needed to define the trajectory. Path of bulletHorizonWind shieldDistance along path ofbullet to window, 23.9”Distance alonghorizon towindow, 23.5”yx60 feetTwo reference points are needed to define the trajectory.Investigators can figure the shooter discharged the firearm somewhere along that line.
49 Trajectory Reference points can be bullet holes in objects or victims. An entry point and exit point on a victim can be used.Gunshot residue or spent cartridge casings can be less specific reference points.Investigators can use lasers to trace a straight-line path to help determine the position of the shooter.
50 Trajectory Determining the Location of the Shooter Using the illustration on Slide 11 and adding that the shot came from a nearby building, these conclusions can be made:Since the building is about 60 feet away, the shooter was about 11 feet above the bullet hole in the seat, which was 4 feet above the ground.This height of about 15 feet off the ground puts the shooter on the second floor in that building.
51 Bullet WoundsWhy do entrance wounds tend to be smaller than exit wounds?If the bullet penetrates clothing, what can fibers embedded in the wound indicate?Where is gunshot residue usually found?If the gun is fired with the muzzle touching the victim’s skin, what telltale mark may show up?Will larger or will smaller caliber bullets tend to lodge within the body rather than passing through? Why?
52 Front line (18 min)Trayvon Martin- bullet distance intermediate -cnn (hoodie/florida 2012)Washington post may 18-“A lab report, based on an examination of the two sweatshirts Martin was wearing, found holes and gunshot residue consistent with a “contact shot,” meaning the gun was pressed against Martin’s chest. An autopsy report said that the gunshot wound indicated he was shot from an “intermediate range,” which experts say is between one and 18 inches away.”