essential question:
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Essential Question:. Ballistics and Arson. How are incidences involving ballistics and arson investigated?. Introduction. Forensic ballistics : the science of analyzing firearm usage in crimes Ballistic evidence helps explain: What type of firearm was used. The caliber of the bullet. - PowerPoint PPT PresentationTRANSCRIPT
Essential Question:How are incidences involving
ballistics and arson investigated?
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Ballistics and Arson
Introduction Introduction Forensic ballistics: the science of analyzing firearm usage in
crimesBallistic evidence helps explain:
What type of firearm was used. The caliber of the bullet. The number of bullets fired. Physical position of the shooter. Whether a weapon was fired recently. If a firearm was used in previous crimes.
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Types of Legal Firearms1. Handguns and pistols: designed to be
handheld (rifled to increase accuracy)– Revolvers: has a cylinder that hold
the bullets (usually 6)• Manually reloaded
– Semiautomatic: shoots one cartridge at a time
• Reloads automatically• Fully automatic weapons keep firing as
long as the trigger is held down
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2. Rifles– Longer barrel– Butt stock to steady the firearm and minimize
kickback– Greater range & accuracy than a handgun
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Types of Legal FirearmsRifling: Make spiral grooves to make a bullet spin and thereby have greater accuracy over a long distance.
Types of legal firearms
3. Shotguns–Like rifles but shoot pack of shot or
spherical pellets–Barrel is not rifled
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4. Air guns or BB guns–Pellets propelled by pressurized air,
spring compression, battery operated or carbon dioxide cartridges
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Types of Legal Firearms
Ammunition Ammunition • Ammunition consists of a cartridge case,
primer, propellant, and a projectile (bullet)• Ammunition is named by its length and
diameter (caliber)
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• Most bullets made of lead– Can be coated with brass,
copper, or steel
• Vary in shape & size– Hallow points: hole causes
bullet to deform upon impact in order to decrease penetration & cause greater harm
Ammunition Ammunition
Assignment for Today
• Work on Ballistics Vocab
Forensic Science: Fundamentals & Investigations, Chapter 17
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How a Firearm Works 1. Firing pin of gun hits the base of
the cartridge, igniting the primer powder.
2. The ignited primer powder sparks through the flash hole, causing the main propellant supply (gunpowder) to ignite
3. The pressure of the explosion pushes the bullet from the casing into the barrel.
4. The bullet follows the lands and grooves spiraling out of the barrel.
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CaliberCaliber: measure of the diameter of the bullet cartridge (also the diameter of the firearm’s barrel or bore)Measured in hundredths of an inch.Common calibers include 0.22, 0.25, 0.357, 0.38, 0.44, and 0.45.
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Grooves, Lands, & Rifling
Grooves and lands in the barrel of a gun produce the twisting that adds accuracy.
The rifling leaves a pattern on the bullet which can be traced back to the specific gun
Bullet Features To AnalyzeIndividual
characteristics• Scratches or striae on
the bullet caused by gun barrel– A microscope is used
to identify & compare these marks
Class characteristics• Weight• Dimensions• Shape• Type of bullet
– Used to help determine the type of ammunition used
• Lands and grooves– Used to identify the make and model of
a weapon
Matching grooves (indentations)
Matching lands (elevations)
Cartridges Cartridges
• Consist of: bullet & case that contains the powder & primer• Most cartridges have primer in the center (centerfire); some
use primer on the circumference of the base (rimfire)
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Cartridge Features To AnalyzeClass characteristics:• Dimensions• Rimfire or centerfire• Head stamp (imprint)
Individual characteristics:• Impression from firing pin
• Breech marks & Extractor Marks– Marks left by gun as bullet is fired
• Scratches caused by movement in magazine or chamber
Methods of analyzing ballistics
• Ballistic gel block• Water tank• Gauze packing• Rubber balls
Gunshot Residues Gunshot Residues
GSRParticles of unburned powder and traces of smoke from gunshot
Found on shooter: HandArmFaceHairClothing
Traces on the victim as well GSR can be used to determine the distance between the victim and the shooterEasily transferred 19
GSR Testing
Greiss TestTest for presence of nitriteCheck for color change: orange-red
Sodium RhidizonateTest for the presence of leadCheck for color change: purple
Forensic Science: Fundamentals & Investigations, Chapter 17
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Gunshot Residues Gunshot Residues Residues from gunshots = particles of unburned powder and traces of smokeThey can leave a trace on the hand, arm, face, hair, or clothing of the shooter. They can also leave a trace on the victim. Chemical testing often can detect residue even if removal is attempted. The distance from the victim to the shooter can be determined by examination of the residue pattern on the victim.
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Trajectory Trajectory
Two reference points are needed to define the trajectory. Investigators can figure the shooter discharged the firearm somewhere along that line.
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Path of bullet
Horizon
Wind shield
Distance along path of bullet to window, 23.9”
Distance along horizon to window, 23.5”
yx
60 feet
Trajectory 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.
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Bullet Wounds Bullet Wounds 1. Why do entrance wounds tend to be smaller than
exit wounds?
2. If the bullet penetrates clothing, what can fibers embedded in the wound indicate?
3. Where is gunshot residue usually found?
4. If the gun is fired with the muzzle touching the victim’s skin, what telltale mark may show up?
5. Will larger or will smaller caliber bullets tend to lodge within the body rather than passing through? Why?
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Arson
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Establish point of origin
Determine possible cause of
fire
Accident, natural or deliberate?
Arson: Terms to KnowArson: crime of maliciously, voluntarily & willfully setting fire to propertyFire: produced when a substance undergoes rapid oxidation involving heat and light. Flashpoint: lowest temperature at which a substance can ignite
Color of flames can be used to tell temp. of fire
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Arson: Terms to KnowPoint of Origin: location where fire startedBurn patterns: noticeable patterns created by fire as it burns
Fire normally burns in a V-shaped pattern
Accelerants: substances, such as gasoline, paint thinner, & alcohol, that accelerate the burning process
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FUEL
OXYGENHEAT
The FIRE TRIANGLE represents the three elements needed for fire to occur:
heat, fuel, and oxygen
The Fire TriangleOxygen: enough O2 must be present to sustain combustion (at least 16%)Fuel: some sort of flammable fuel must be presentHeat: enough heat must be produced to ignite the fuel source
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Motives for ArsonInsurance FraudAttempt to harm person &/or their propertyRevenge: accounts for 50% of arson casesConceal crime: robbery, murderTerrorismPyromania
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Arson Indicators2 or more points of origin2 separate, non-related firesTrailers = ribbon or linear pattern of spread of fire: indicates that fire followed an accelerantOdors: gas, kerosene or other accelerantsFurnishings & valuables removedLocked windows & blocked doors
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Arson: Methods of DetectionPhysical evidenceDogs: smell for accelerantsPortable gas detections aka “sniffers”Gas chromatography: chemical analysis of accelerants & burned remains
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Causes of Accidental FiresHeating systemDryerLightningElectronicsSmoking
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Assignments for Today
• Fire Crossword Puzzle• Begin Ballistics & Arson Review
Forensic Science: Fundamentals & Investigations, Chapter 17
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• You need to remain silent & pay attention during notes• You SHOULD NOT be talking to your neighbors or having “silent” conversions
across the room• Raise your hand if you have a question or comment• If I see or hear your talking:
1. Verbal warning2. Silent lunch3. Classroom detention4. Leave room & write-up
• CELL PHONES NEED TO BE PUT AWAY!
Reminder: No talking during Notes (Lecture)
Depending on prior disciplinary actions
Investigating Criminal Bombing
• Evidence:– Presence of scattered bomb fragments– Trained dogs detect traces of explosive material
• Need safety precautions for crew due to:– structural instability of buildings– dangerous materials such as glass and metal– flammable or toxic substances
• Always a possibility that a second device – May kill or maim those who respond to the explosion
Criminal Bombing
• Richard Reid • Shoe bomb attempt• Suspicious individual: loner, fidgety, sweaty• Result: we take shoes off at the airport
• Eric Rudolph• 1996 Centennial Olympic Park bombing• Suspicious unattended bag• Killed 1 and injured 111 people
Criminal Bombing• Ted Kaczynski, the Unabomber
– Lived in a mountain cabin in Montana– Mail bombs– Killed 3 and injured 23 people
• Timothy McVeigh– Oklahoma City bombing– Truck Bomb– Killed 168 and injured over 800 people
End of Unit 5 Notes!
• Reminders: – Do the Ballistics & Arson Review!– Study your notes, worksheets, and handouts!
• Ballistics & Arson Review Lab
Forensic Science: Fundamentals & Investigations, Chapter 17
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4 Corners• You have two minutes to contemplate this
question:– Which of these factors of investigating criminal
bombing is most important?• Crew Safety: protecting those investigating the
bombing• Suspect profiling• Attending to victims• Collecting/Preserving PhysicalEvidence
• Find the corner of the room with the answer you chose
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Jigsaw• Read the text provided to your group• Create a small poster with vital information
about arson to present to the class• Poster must include: Use Markers
– A title– a picture or diagram related to your topic– A brief summary of topic and specific
terminology of note
• Be prepared to present your topic during the last 15 minutes of class 41
Ballistics and ArsonGeorgia Performance Standards
• SFS4 Students will evaluate the role of ballistics, tool marks and evidence of arson in
• forensic investigation.• a. Identify firearm lab tests used to distinguish the characteristics
of ballistics and • cartridge cases.• b. Analyze the physics of ballistic trajectory to predict range of
firing.• d. Evaluate possible indicators of arson and criminal bombing.
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