Presentation on theme: "How are incidences involving ballistics and arson investigated?"— Presentation transcript:
1How are incidences involving ballistics and arson investigated? Essential Question:How are incidences involving ballistics and arson investigated?
2IntroductionForensic 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.
3Types 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 reloadedSemiautomatic: shoots one cartridge at a timeReloads automaticallyFully automatic weapons keep firing as long as the trigger is held downRevolvers: six shootersRifling decreases wobbling in flight by putting a spin on the projectile like throwing a footballPic- Walther P99 German semiautomatic pistol
4Types of Legal Firearms Rifling: Make spiral grooves to make a bullet spin and thereby have greater accuracy over a long distance.2. RiflesLonger barrelButt stock to steady the firearm and minimize kickbackGreater range & accuracy than a handgunPic-hunting rifle
5Types of legal firearms 3. ShotgunsLike rifles but shoot pack of shot or spherical pelletsBarrel is not rifledBottom Pic-browning A-5 semi automatic shotgun
6Types of Legal Firearms 4. Air guns or BB gunsPellets propelled by pressurized air, spring compression, battery operated or carbon dioxide cartridgesPic-bb pistol w/ CO2 magazines
7AmmunitionAmmunition consists of a cartridge case, primer, propellant, and a projectile (bullet)Ammunition is named by its length and diameter (caliber)over 300 kinds of ammunition for just handgunsDiameter is known as caliber
8Ammunition Most bullets made of lead Vary in shape & size Can be coated with brass, copper, or steelVary in shape & sizeHallow points: hole causes bullet to deform upon impact in order to decrease penetration & cause greater harm
9Forensic Science: Fundamentals & Investigations, Chapter 17 Assignment for TodayWork on Ballistics VocabForensic Science: Fundamentals & Investigations, Chapter 17
10How a Firearm WorksFiring pin of gun hits the base of the cartridge, igniting the primer powder.The ignited primer powder sparks through the flash hole, causing the main propellant supply (gunpowder) to igniteThe pressure of the explosion pushes the bullet from the casing into the barrel.The bullet follows the lands and grooves spiraling out of the barrel.
11CaliberCaliber: 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.
13Grooves, 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
14Bullet Features To Analyze Individual characteristicsScratches or striae on the bullet caused by gun barrelA microscope is used to identify & compare these marksClass characteristicsWeightDimensionsShapeType of bulletUsed to help determine the type of ammunition usedLands and groovesUsed to identify the make and model of a weaponStriae used to match two bullets or match a bullet to a firearmUse size, weight, shape, and dimensions to determine the type of ammunitionEx: .357 magnum weighs 10.2gEx: a standard 9mm weighs 6.5gLands and grovesEx: the .32 caliber S & W handgun has five lands and grooves with a right hand twistEx: the .32 caliber Colt has 6 lands and grooves with a left-hand twist.Matching grooves (indentations)Matching lands (elevations)
15Cartridges 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)
16Cartridge Features To Analyze Class characteristics:DimensionsRimfire or centerfireHead stamp (imprint)Individual characteristics:Impression from firing pinBreech marks & Extractor MarksMarks left by gun as bullet is firedScratches caused by movement in magazine or chamberStriae used to match two bullets or match a bullet to a firearmUse size, weight, shape, and dimensions to determine the type of ammunitionEx: .357 magnum weighs 10.2gEx: a standard 9mm weighs 6.5gLands and grovesEx: the .32 caliber S & W handgun has five lands and grooves with a right hand twistEx: the .32 caliber Colt has 6 lands and grooves with a left-hand twist.
18Methods of analyzing ballistics Ballistic gel blockWater tankGauze packingRubber balls
19Gunshot Residues GSR Found on shooter: Traces on the victim as well Particles of unburned powder and traces of smoke from gunshotFound on shooter:HandArmFaceHairClothingTraces on the victim as wellGSR can be used to determine the distance between the victim and the shooterEasily transferredGSR particles blow back onto the shooter
20Forensic Science: Fundamentals & Investigations, Chapter 17 GSR TestingGreiss TestTest for presence of nitriteCheck for color change: orange-redSodium RhidizonateTest for the presence of leadCheck for color change: purpleForensic Science: Fundamentals & Investigations, Chapter 17
21Gunshot ResiduesResidues 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.
22Trajectory 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.
23Trajectory 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.
24Bullet 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?
25Arson Determine possible cause of fire Establish point of origin Accident, natural or deliberate?
26Arson: 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 igniteColor of flames can be used to tell temp. of fire
27Arson: Terms to Know Point of Origin: location where fire started Burn patterns: noticeable patterns created by fire as it burnsFire normally burns in a V-shaped patternAccelerants: substances, such as gasoline, paint thinner, & alcohol, that accelerate the burning process
28The FIRE TRIANGLE represents the three elements needed for fire to occur: heat, fuel, and oxygenFUELOXYGENHEAT
29The 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
30Motives for Arson Insurance Fraud Attempt to harm person &/or their propertyRevenge: accounts for 50% of arson casesConceal crime: robbery, murderTerrorismPyromania
31Arson Indicators 2 or more points of origin 2 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
32Arson: Methods of Detection Physical evidenceDogs: smell for accelerantsPortable gas detections aka “sniffers”Gas chromatography: chemical analysis of accelerants & burned remains
33Causes of Accidental Fires Heating systemDryerLightningElectronicsSmoking
35Reminder: No talking during Notes (Lecture) You need to remain silent & pay attention during notesYou SHOULD NOT be talking to your neighbors or having “silent” conversions across the roomRaise your hand if you have a question or commentIf I see or hear your talking:Verbal warningSilent lunchClassroom detentionLeave room & write-upCELL PHONES NEED TO BE PUT AWAY!Depending on prior disciplinary actions
36Investigating Criminal Bombing Evidence:Presence of scattered bomb fragmentsTrained dogs detect traces of explosive materialNeed safety precautions for crew due to:structural instability of buildingsdangerous materials such as glass and metalflammable or toxic substancesAlways a possibility that a second deviceMay kill or maim those who respond to the explosion
37Criminal Bombing Richard Reid Shoe bomb attempt Suspicious individual: loner, fidgety, sweatyResult: we take shoes off at the airportEric Rudolph1996 Centennial Olympic Park bombingSuspicious unattended bagKilled 1 and injured 111 peopleGenerally require preventative measuresReid- self proclaimed Al-QaeidaRudolph-Extremist Christian movement-Olympic bombing- originally suspected the officer who found the bomb. He was investigated by FBI for 3 months and ridiculed by the media for longer. Found Rudolph hiding in the woods of North Carolina-he bombed some abortion clinics 2 years later and was linked back to the 1996 bombing.
38Criminal Bombing Ted Kaczynski, the Unabomber Timothy McVeigh Lived in a mountain cabin in MontanaMail bombsKilled 3 and injured 23 peopleTimothy McVeighOklahoma City bombingTruck BombKilled 168 and injured over 800 peopleTed: Sent a narration of his motives to the FBI- They in turn got it published in the Times and Washington Post- Ted’s family recognized his views and beliefs.
39Forensic Science: Fundamentals & Investigations, Chapter 17 End of Unit 5 Notes!Reminders:Do the Ballistics & Arson Review!Study your notes, worksheets, and handouts!Ballistics & Arson Review LabForensic Science: Fundamentals & Investigations, Chapter 17
404 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 bombingSuspect profilingAttending to victimsCollecting/Preserving PhysicalEvidenceFind the corner of the room with the answer you chose
41Jigsaw Read the text provided to your group Create a small poster with vital information about arson to present to the classPoster must include: Use MarkersA titlea picture or diagram related to your topicA brief summary of topic and specific terminology of noteBe prepared to present your topic during the last 15 minutes of class
42Ballistics and Arson Georgia Performance Standards SFS4 Students will evaluate the role of ballistics, tool marks and evidence of arson inforensic investigation.a. Identify firearm lab tests used to distinguish the characteristics of ballistics andcartridge cases.b. Analyze the physics of ballistic trajectory to predict range of firing.d. Evaluate possible indicators of arson and criminal bombing.