座世界名案分析大纲.ppt

Shooting Case Investigation,Dr. Henry C. Lee Chief Emeritus, State Police Lab Professor, University of New Haven Director, Forensic Research & Training Center,Type of firearms,Handguns Rifles Shotguns Submachine guns Machine guns,COMPONENTS OF A FIREARM,BARREL Rifled or Smooth STOCK OR GRIP FIRING MECHANISM Firing Pin, Breech Lock, Ejector, Extractor LOADING MECHANISM Single, Automatic, double barrel MAGAZINE OR CYLINDER,AMMUNITION COMPONENTS,Projectile Bullet, shot pellets, slug Cartridge Case / Shell Primer Center v. Rim fire Powder Black Powder Smokeless (Nitrocellulose base) Wad,BULLETS - PROJECTILES,CALIBER, GUAGE, SHOT SIZE COMPOSITION CLASS CHARACTERISTICS MANUFACTURER, STYLE TYPE WEAPON FIRED FROM INDIVIDUAL CHARACTERISTICS STRIATIONS FROM LANDS & GROOVES,CARTRIDGE CASES,MANUFACTURER CALIBER & LOAD SPECIFICATIONS FACTORY V. RELOAD INDIVIDUAL CHARACTERISTICS FIRING PIN IMPRESSION BREECHFACE MARK CHAMBER MARKS EXTRACTOR / EJECTOR MARKS,WEAPON EXAMINATIONS,FUNCTIONALITY PROPER TRIGGER PULL TRACE / FINGERPRINTS / DNA OWNERSHIP HISTORY,TOOL MARK COMPARISONS,TYPES Indentations, Striations DOCUMENTATION Photos, Seize item, Casts, REPRODUCTION / EXEMPLARS Suspect tool, similar surface-motion-pressure TRACE ANALYSIS Paint analysis COMPARISON MICROSCOPE NUMBER RESTORATIONS,Serial Number Restoration,Polish surface Apply etching acid,Shooting Incident Reconstruction,Shooter location / position determination Victim location / position determination Homicide / Suicide /Accidental death Trajectory determination Distance determination Spatial and sequence determination,Communication with HQ Aid victims Locate witnesses Secure the scene Transfer officer involved crowd control Documentation of the scene Collection of physical evidence Initiate investigation,Information,witness,statements,Theory,Record File,scene,Laboratory results,Physical evidence,Gunshot wounds,Kinetic Energy Of A Projectile,K.E. = M V,Classification of Gunshot Wounds,Contact wounds Near contact wounds Intermediate Gunshot wounds Distant wounds,Wound Evidence,Entrance wound Abrasion Rings Powder Soot Power particles,Exit Wound Trace Material Pseudo-Powder Tattooing Bullet Wipe,SHOT GUN INJURY PATTERN,TYPES,Contact Discharge Close Discharge Mid-range Discharge Distance Discharge,Contact Discharge,Muzzle against the skin Single and circular wound Entrance hole approximate diameter of bore Little or no soot on skin Little or no burn on skin Muzzle mark on skin GSR in wound track,Close Range Discharge,Muzzle near skin (not a contact) Circular Wound right angle Elliptical wound slanted angle Nibbling / cremation around wound edge Blackened / soot on edge of wound Annular / distant bruising Singeing of hair / skin GSR around wound,Mid-range Discharge,Smoke / soot diminished 20-40cm Muzzle to target 15cm to 2 m Powder tattooing around wound 20-6- cm Cremated / scalloped wound edges One central entrance hole 1m Satellite holes around central hole 1m,Distance Discharge,Muzzle to target - 2m No burning / soot on skin Few GSR particles Wad may be present 5m Central hole diminished 6- 10 m Spread of pellets increase,Trace Evidence in Shooting Cases,Residues on Bullet and Casing Residues along Projectile path GSR on Hands GSR on Clothing GSR on Target Blood Spatters on Body and Scene Trace materials on Clothing Blood, Tissues on Weapon,Trace and Transfer Evidence,Hair Fibers Tissues Salvia,Bloodstains GSR Patterns Soil Stain Grass Stain,GSR (Gun Shot Residue) Deposits,GSR from Muzzle Powder Particles on Target (Body, Wound, Clothing, Object, Surfaces) GSR from Cylinder gap GSR particles on Hands, Clothing,GUN SHOT RESIDUE,BURNED & UNBURNED POWDER PARTICLES PRIMER RESIDUE: LUBRICANTS BARREL RESIDUES / TRANSFERS PROJECTILE WIPES / TRANSFERS,Bullet Trajectory Determination,Probe String laser,Alignment of laser beam Documentation of laser beam Positioning stages Angular information from the aligned beam Interposition of objects in the laser beam The use of hollow probes with laser beam Dual- opposed co-axial laser beam High ambient light level, auxiliary alignment target,Problems associated with shooting reconstructions,Damage to the bullet Through and through shots Alteration of pattern evidence Inability to recover evidence alteration of physical evidence Misinterpreted information,General Consideration of Ricochet,The projectile will lose some energy The depart is usually different than the incident angle The projectile usually has deformation Trace transfer evidence usually presence Impact surface may play important role,Laws of Physics on Ricochet,The Steeper the incident angle, the greater the force acting on the bullet at impact. The greater the impact on the bullet results the greater loss of velocity and the greater deformation to the bullet.,Important Terms,Incident Angle vs. Departure Angle, Critical Angle Pinch Point, Bow effect & Chi sum Trail Lead Splash vs. Lead wipe Hard Surface vs. Soft Surface,Ricochet & Deflection,Ricochet is the continued flight of a rebounded projectile after an actual angle impact of a surface or object. Deflection is a deviation in the projectiles normal path as a consequence of an impact. 1. As a consequence of a ricochet 2. As a consequence of a penetration,Examination of Ricochet Bullet,Bullet Deformation Bullet Destabilization Bullet Deflection,Bullet Ricochet Surface,1. Yielding Surface: Soil, Sand, Water, Tissue, Sheet Metal, Wood, Drywell 2. Frangible Surface: Cinder Blocks, Bricks, Stepping Stone, Procaine Surface 3. Non Yielding Surface: Stone, Concrete, Steel, Heavy Metal,Portland - A Shooting Investigation,D