Physical Evidence bsapp.com.

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Presentation transcript:

Physical Evidence bsapp.com

Types of Analysis Comparison Visual Microscopic Chemical bsapp.com

Most types of evidence require a control with which to be compared Comparison bsapp.com Most types of evidence require a control with which to be compared

Evidence utilized through unaided observation Visual Analysis Evidence utilized through unaided observation bsapp.com

Evidence observed with the use of some type of microscope Microscopic Analysis Evidence observed with the use of some type of microscope bsapp.com

Evidence subjected to any type of chemical procedure Chemical Analysis Evidence subjected to any type of chemical procedure bsapp.com

Types of Evidence bsapp.com

Documents Hand written Type or Printed Authenticity? bsapp.com

Glass How broken? (Small hole? Big pieces? Inside or outside?) Link a suspect to a crime scene Fingerprints Blood bsapp.com

Soils, Minerals, Wood, and Other Vegetative Matter. Location Link suspect Trace Evidence bsapp.com

Fingerprints Mainstay of Forensics Who is on file? bsapp.com

Hair What type? How removed? Match to a person DNA bsapp.com

Fibers Link suspect to a location or victim Origin? bsapp.com

Firearms and Ammunition Circumstances of discharge Link to suspect Link to weapon Link to victim bsapp.com

Powder Residue GSR Test Evidence of shooting Circumstances of shooting Type of weapon bsapp.com

Explosives & Propellants Link to suspect or victim Origin bsapp.com

Tool Marks Match tool to scars bsapp.com

Impressions bsapp.com

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Drugs Type of Drug? Strength? Origin? Legal? bsapp.com

Paint Origin Match bsapp.com

Blood, Semen, Saliva, Organs, & other Physiological Fluids Origin DNA Condition bsapp.com

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1. What are the four types of analysis. 2 1.What are the four types of analysis? 2.Explain what “tool marks” are and how they are used in CSI.

What does a CSI observe with each of the following evidences? Documents Broken glass Vegetative & soil samples Hair Fiber Firearms and ammunition Powder residue Impressions Drug samples Body fluid

Glass Fractures bsapp.com

A burglar shatters a window A burglar shatters a window. Later, police discover glass fragments embedded in his shoes and jacket. A shooter fires bullets through a window but claims someone inside shot at him first. Cracked, fractured or shattered glass yields crucial clues for investigations of crimes and accidents. Forensic glass analysis uncovers those clues using a variety of scientific processes. Forensic analysis of glass fractures reveals clues about projectiles, weapons and direction of force.

Glass How broken? Link a suspect to a crime scene Fingerprints Blood bsapp.com

Radial cracks look like spokes in a bicycle tire, while concentric cracks resemble ripples in a pond. Add gunpowder residue, and there is no doubt someone fired a gun.

Fractures Concentric Radial bsapp.com

Direction of Penetration Glass bends in response to a force exerted on its surface. When the limit of its elasticity is reached the glass will fracture. A projectile hole is inevitably wider at the exit side. Often difficult to determine the size and shape of hole in glass whether it was made by bullet or by some other projectile. bsapp.com

Stress Marks A projectile hole is inevitably wider at the exit side, and hence its examination is an important factor when determining the direction of impact. bsapp.com

Direction of Penetration Radial Concentric bsapp.com

Radials Produced first Form on side of glass OPPOSITE to where impact originated. Like spider webs that spread outward from the impact hole bsapp.com

Concentric Form SECOND Encircle the projectile hole Start on the same side as that of the force. bsapp.com

Successive Penetrations A fracture always terminates at an existing line of fracture bsapp.com

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Glass fragments from a crime or accident scene sometimes stick to weapons, tools, automobiles or clothing. Forensic glass examiners compare the density of glass fragments--typically, one sample from a suspect and one from the scene of the accident or crime. If the densities fail to match, police may have enough information to exclude fragments as coming from the crime scene source. However, identical densities do not indicate a match, since many types and samples of glass may share the same density. Therefore, forensic glass examiners also analyze the refractive index of both samples. Refractive index measures the ratio of the velocity of light as it passes through a medium versus through a vacuum. A match in refractive index may mean that two glass samples came from the same source, although no glass expert can proclaim that with 100 percent certainty.