ForensicsPhysical Evidence

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Chapter 5

• Forensics/Physical Evidence

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Types of Evidence

• Physical Evidence
• Anything that is real (it has substance)
• Can be seen, touched, smelled, or tasted
• Direct Evidence
• Establishes proof of a fact without other
  evidence
• Circumstantial/Indirect Evidence
• Evidence from which inferences are drawn

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Types of Evidence cont.

• Trace Evidence
• Extremely small items like hairs and fibers
• Prima Facie Evidence
• Evidence established by law
• 0.8 BAC intoxication
• Associative Evidence
• Links a suspect with a crime
• Fingerprints, bloodstains, hairs and fibers

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Types of Evidence cont.

• Corpus Delicti Evidence
• Establishes that a crime has been committed
• Supports the elements of the crime
• Exculpatory Evidence
• Physical evidence that clears one of blame

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Processing Physical Evidence

• Discovering, recognizing and examining it
• Collecting, recording and identifying it
• Packaging, conveying and storing it
• Exhibiting it in court and
• Disposing of it when the case is closed.

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Evidence

• Material Evidence evidence that is relevant to
  the specific case and forms a substantive part of
  the case or that has a legitimate and effective
  influence on the decision of the case
• Relevant Evidence evidence that applies to the
  matter in question
• Competent Evidence evidence that has been
  properly collected, identified, files and
  continuously secured

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Common Errors in Collecting Evidence

• Not collecting enough of the sample
• Not obtaining standards of comparison
• Not maintaining the integrity of the evidence

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Daubert Standard

• Two-prong standard
• Expert testimony must be reliable.
• Expert testimony must be relevant.

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Determining Reliability

• Can the scientific theory or technique be tested
  and has it been tested?
• Has it been the subject of publication or peer
  review?
• What is the known or potential rate of error?
• What are the standards controlling the
  techniques operation?
• Has the theory or technique been generally
  accepted in the scientific community?

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Frequently Examined Evidence
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Types of Fingerprints

• Latent fingerprints impressions transferred to a
  surface
• Visible fingerprints prints made when fingers
  are dirty or stained

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Types of Fingerprints cont.

• Plastic fingerprints impressions left in soft
  substances
• Invisible fingerprints prints that are not
  readily seen but can be developed through powders
  or chemicals

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Dusting for Fingerprints

• Make sure the brush is clean
• Shake the powder can to loosen powder
• Remove all excess powder
• Photograph

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Frequently Examined Evidence I

• Fingerprints
• Voiceprints
• Language Analysis
• DNA Profiling
• Blood and Other Body Fluids
• Hairs and Fibers

• Shoe and Tire Impressions
• Bite Marks
• Tools and Tool Marks
• Firearms and Ammunition

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DNA-deoxyribonucleic acid

• Genetic fingerprint to positively identify a
  person
• Nuclear DNA
• Blood, saliva, semen, body tissue, hair root
• Mitochondrial DNA
• Bones, teeth, hair fragments, naturally shed hair

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Blood

• Blood
• Establish if violent crime was committed
• Recreates movements of suspect/victim
• Eliminate suspects
• Luminol
• Presumptive positive test for blood
• Causes blood to fluoresce pale blue color
• Detect blood diluted up to 10,000 times
• Does not harm DNA in blood

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Hairs and Fibers

• Hair examination
• Determine if animal or human
• What part of body it came from
• Dyed or bleached
• Freshly cut, pulled or burned
• Race, sex and age cannot be determined

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Hairs and Fibers cont.

• Fibers
• Four groups of fibers
• Mineral (Asbestos and glass)
• Vegetable (Cotton and Hemp)
• Animal (Wool and Silk)
• Synthetic (Rayon, polyester, and nylon)
• More distinguishable than hair
• Can be tested for origin and color
• Most frequently located microscopic evidence

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Firearm Properties

• Make
• Serial Number
• Caliber
• Model
• Type
• Finish
• Any Unusual Characteristics

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Firearm Terminology

• Bore the diameter of the inside of a weapons
  barrel
• Lands two opposing ridges in the barrel
• Striations scratches on recovered bullets
• Caliber the diameter of the bullet intended to
  be used with a specific weapon

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Firearms-Evidence Collection

• NEVER put an object inside the barrel to pick it
  up
• Marking made by rifling, extraction, and ejection
  mechanisms can ID weapon
• Gunshot Residue (GSR)
• Discharged gunpowder and primer causes gaseous
  cloud up to 5 ft from firearm
• Settles on shooter (hands, face, sleeves, etc.)
• Abundance of GSR on victim suicide

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Firearms-Evidence Collection cont.

• Laboratory examination of GSR
• Scanning electron microscope (SEM)
• Locates and identifies specific residue particles
  and their composition
• ATF and NIBIN (National Integrated Ballistic
  Information Network)
• National database created to link firearms with
  offenders

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Frequently Examined Evidence II

• Glass
• Soils and Minerals
• Safe Insulation
• Ropes, Strings, and Tapes
• Documents
• Best evidence rule

• Drugs
• Laundry and Dry-cleaning Marks
• Paint
• Skeletal Remains
• Wood
• Other types

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Glass

• Microscopic examination proves that two pieces
  were once one piece
• Spectrographic analysis determines the elements
  of the glass
• Physical comparisons

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Skeletal Remains

• Forensic anthropology uses techniques that have
  been developed during decades of research by
  physical anthropologists and archaeologists
• Lab exam can determine
• Animal or human
• Sex, race, approx. age
• Approx. height and approx. time since death

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Skeletal Remains cont.

• Forensic entomology the science of studying
  insects found at the scene of a death

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Evidence Admissibility in Court

• Identify the evidence as that found at the crime
  scene
• Describe where it was found
• Establish the chain of custody from discovery to
  the present
• Explain any changes that have occurred in the
  evidence

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