Ballistics and Arson Essential Question How are incidences

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

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

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

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

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

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

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

Ammunition • 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

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

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

Caliber: 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. 11

Grooves, Lands, & Rifling l Grooves and lands in the barrel of a gun produce the twisting that adds accuracy. l The rifling leaves a pattern on the bullet which can be traced back to the specific gun

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 Matching lands (elevations) Matching grooves (indentations) 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

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

Cartridge Features To Analyze Class characteristics: Individual characteristics: • Dimensions • Impression from firing pin • Rimfire or centerfire • Head stamp (imprint) • 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 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

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

Gunshot 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

Trajectory Wind shield Distance along path of bullet to window, 23. 9” Path of bullet x y 60 feet Horizon Distance along horizon to window, 23. 5” Two reference points are needed to define the trajectory. Investigators can figure the shooter discharged the firearm somewhere along that line. 22

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

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? 24

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

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

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

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

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

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

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

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

Causes of Accidental Fires Heating system Dryer Lightning Electronics Smoking 33

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

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

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 Mc. Veigh – 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 39

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 Physical. Evidence • Find the corner of the room with the answer you chose 40

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 Arson Georgia Performance Standards • SFS 4 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