Unit 2: Physical Evidence Fingerprinting, Ballistics, & Blood Spatter

1. Unit 2: Physical EvidenceFingerprinting, Ballistics, & Blood Spatter

2. History of Fingerprints Pgs. 134-135

3. Summary of Will West Case Study

4. History of Fingerprints: Cont’d Pg. 134

5. What is a fingerprint?? Develop 6-13 weeks during fetal development • Papillae- boundary between the epidermis and the lower dermis • Forms its own ridge pattern • Sweat gland coats surface of fingers with perspiration • Consists of water, salts, other organic material • Water evaporates and left with fingerprint when fingers touch surface Papillae In order to remove fingerprint, you would have to remove skin BELOW the papillae!

6. Types of Fingerprints • Whorl- core closed in center • ~ 33% of people have these Ridge Core

7. Types of Fingerprints Loop- one or more ridges entering one side, curve, then leave from the same side it entered ~65% population has loop Core Ulnar Loop- Loop extends toward pinky Radial Loop- loop extends toward thumb Right hand

8. Types of Fingerprints Arch- ridges enter one side and exit on the opposite side while rising in the middle ~5% population Plain Arch Tented Arch

9. Fingerprint Ridge Classification: Minutiae Pg. 139

10. Types of Fingerprints Lifted from Crime Scene • Visible- see them • Blood, chalk, grease • Plastic- impressions • Wax, soap • Latent- cannot see • Caused by perspiration, powders, fuming • Visualizing latent prints • Dusting • Hard, non-absorbent surfaces • Different colored powders • Fuming • Nonporous surfaces, super glue • Lasers

11. Fingerprinting • AFIS- automated fingerprint ID system • FBI- keeps and maintains files • Search time- immediate • Matching and legal considerations

12. Ballistics & Firearms • Why are guns/bullets so important to know about in forensics?

13. Forensic Firearm Examiners Analyze 1. Ballistics 2. Guns, Bullets, and Shell Casings Class Evidence: Determine what kind of gun fired the bullet Individual Evidence: Match bullet or shell casing to A specific weapon A sample from a different crime scene to link the two Ballistics: how bullets behave after being fired • Estimate • Distance between gun muzzle and victim • Trajectory of bullets Parabolic Motion

14. Gun Anatomy & Terminology 2. 14. 13. 1. Muzzle: 2. Barrel: 3. Safety: 4. Hammer: 5. Trigger: 6. Magazine: 7. Bore: 8. Land: 9. Groove: Rifling Twist: clockwise or counterclockwise Caliber: Butt stock: 13. Action: 14. Breech: 4. 1. 2. 3. 5. 5. 6. 12. 7. 8. 9.

17. Ammunition Primer Bullet caliber: diameter of bullet

18. Name that Type of Bullet

19. How a Gun Works Breech • Overall: Burn fuel, creates gas pressure, projectile launches • Load ammunition • Pull trigger • Hammer hits cartridge case • Primer ignites, sets off gun powder • Bullet forced forward through grooved barrel spin Longer barrel: from gas pressure- more accurate, travel farther Action

20. Class Characteristics: Match Bullet to Type of Gun • Manufacture • Winchester • Shape • Rimless, rimmed • Caliber • Diameter of bullet • Composition • Brass, steel, plastic

21. Individual Characteristics: Matching a Bullet to a Specific Gun • Striations : Markings on a bullet created by the lands and grooves (rifling) in the barrel as the bullet travels out • No rifling is exactly the same from one gun to the next (like a fingerprint) A B

22. Individual Characteristics: Matching a Bullet to a Specific Gun • Breech marks- marks left on back of cartridge casing • As bullet moves forward, casing moves backward against breech making an impression

23. Individual Characteristics: Matching Bullets to a Specific Gun • Firing pin marks • Marks created by the firing pin as it strikes the bottom of the cartridge when shot • Extractor & ejector marks • Marks left when bullet casing released after gun fired

24. Residue from Guns • Gunpowder thrown backward and forward • Infrared photography reveals residue patterns • Can determine how far away a shot was fired from • Halo of soot around hole = 12-18” away • Halo with specks = 18-25” away • Only specks = 26 +” away

25. Examination & Use in Court • Use of comparison microscope • No rules on number of points of comparison • FBI maintains records of class characteristics of all weapons: IBIS

26. Blood Spatter: Intro • Blood • Surface tension- blood sticks to itself on the outer part • As blood falls, it stays together to form sphere • Force from impact breaks the surface tension creating blood spatter patterns

27. Blood Spatter Analysis Multiple Drop Patterns As one adds more drops of blood to a pool of blood the size of blood on the surface _________ and there are a greater number of ________ ____________ Patterns on Various Surfaces The more porous (more holes on the surface), the more ____________ the blood becomes. Height As height increases, the diameter of the drop __________ and there are a greater number of _________. Porous or nonporous?_________

28. Blood Spatter Analysis Determining the victim’s position 1. Direction of Travel • Tail points in direction of travel 2. Angle of Impact

29. Blood Spatter Analysis Determining the victim’s position: Cont’d 3. Position of Origin • Tracing pattern back to source/area of convergence

30. Blood Spatter Analysis Blood Droplet Speed Before Impact

31. Blood Spatter Analysis Arterial Spurt Arterial Spurt- How blood leaves body: Why leave this way Describe pattern Cast Off Cast off: How to Recognize Pattern

32. Blood Spatter Analysis Transfer Pattern • Transfer pattern: • Draw example of knife transfer Swipe/Wipe • How swipe different from a wipe

33. Blood Spatter Analysis Point of Impact • Point of impact/origin: Shadowing/Ghosting • Shadowing/ghosting: • What is the evidence of shadowing/ghosting?

34. Blood Spatter Analysis From: Science of Murder (Las Vegas TV 13: Crime Team) • Materials used to investigate blood spatter • Why? • Weapon with medium blood spatter • What does stringing tell you? • How to distinguish walking and running person using blood spatter • Chemical to ID blood: • What look like in presence of blood: