Essential Question:

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

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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

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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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