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Essential Question: How are incidences involving ballistics and arson investigated? 1 Ballistics and Arson.

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Presentation on theme: "Essential Question: How are incidences involving ballistics and arson investigated? 1 Ballistics and Arson."— Presentation transcript:

1 Essential Question: How are incidences involving ballistics and arson investigated? 1 Ballistics and Arson

2 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. The number of bullets fired. Physical position of the shooter. Whether a weapon was fired recently. If a firearm was used in previous crimes. 2

3 Types of Legal Firearms 1. 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 3

4 2. Rifles – Longer barrel – Butt stock to steady the firearm and minimize kickback – Greater range & accuracy than a handgun 4 Types of Legal Firearms Rifling: Make spiral grooves to make a bullet spin and thereby have greater accuracy over a long distance.

5 Types of legal firearms 3. Shotguns – Like rifles but shoot pack of shot or spherical pellets – Barrel is not rifled 5

6 4. Air guns or BB guns – Pellets propelled by pressurized air, spring compression, battery operated or carbon dioxide cartridges 6 Types of Legal Firearms

7 Ammunition Ammunition consists of a cartridge case, primer, propellant, and a projectile (bullet) Ammunition is named by its length and diameter (caliber) 7

8 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

9 Assignment for Today Work on Ballistics Vocab Forensic Science: Fundamentals & Investigations, Chapter 17 9

10 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. 10

11 Caliber Caliber: measure of the diameter of the bullet cartridge (also the diameter of the firearms barrel or bore) Measured in hundredths of an inch. Common calibers include 0.22, 0.25, 0.357, 0.38, 0.44, and


13 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

14 Bullet Features To Analyze Individual 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)

15 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) 15

16 Cartridge Features To Analyze Class 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


18 Methods of analyzing ballistics Ballistic gel block Water tank Gauze packing Rubber balls

19 Gunshot Residues GSR Particles of unburned powder and traces of smoke from gunshot Found on shooter: Hand Arm Face Hair Clothing Traces on the victim as well GSR can be used to determine the distance between the victim and the shooter Easily transferred 19

20 GSR Testing Greiss Test Test for presence of nitrite Check for color change: orange-red Sodium Rhidizonate Test for the presence of lead Check for color change: purple Forensic Science: Fundamentals & Investigations, Chapter 17 20

21 Gunshot Residues Residues from gunshots = particles of unburned powder and traces of smoke They 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. 21

22 Trajectory Two reference points are needed to define the trajectory. Investigators can figure the shooter discharged the firearm somewhere along that line. 22 Path of bullet Horizon Wind shield Distance along path of bullet to window, 23.9 Distance along horizon to window, 23.5 y x 60 feet

23 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. 23

24 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 victims 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? 24

25 Arson 25 Establish point of origin Determine possible cause of fire Accident, natural or deliberate?

26 Arson: Terms to Know Arson: crime of maliciously, voluntarily & willfully setting fire to property Fire: 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 26

27 Arson: Terms to Know Point of Origin: location where fire started Burn 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 27

28 FUEL OXYGENHEAT The FIRE TRIANGLE represents the three elements needed for fire to occur: heat, fuel, and oxygen

29 The Fire Triangle Oxygen: enough O 2 must be present to sustain combustion (at least 16%) Fuel: some sort of flammable fuel must be present Heat: enough heat must be produced to ignite the fuel source 29

30 Motives for Arson Insurance Fraud Attempt to harm person &/or their property Revenge: accounts for 50% of arson cases Conceal crime: robbery, murder Terrorism Pyromania 30

31 Arson Indicators 2 or more points of origin 2 separate, non-related fires Trailers = ribbon or linear pattern of spread of fire: indicates that fire followed an accelerant Odors: gas, kerosene or other accelerants Furnishings & valuables removed Locked windows & blocked doors 31

32 Arson: Methods of Detection Physical evidence Dogs: smell for accelerants Portable gas detections aka sniffers Gas chromatography: chemical analysis of accelerants & burned remains 32

33 Causes of Accidental Fires Heating system Dryer Lightning Electronics Smoking 33

34 Assignments for Today Fire Crossword Puzzle Begin Ballistics & Arson Review Forensic Science: Fundamentals & Investigations, Chapter 17 34

35 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 warning 2.Silent lunch 3.Classroom detention 4.Leave room & write-up CELL PHONES NEED TO BE PUT AWAY! Reminder: No talking during Notes (Lecture) Depending on prior disciplinary actions

36 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

37 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

38 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

39 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 39

40 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 40

41 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

42 Ballistics and Arson Georgia 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. 42

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