Download Unit 1 Safety Issues

Chapter 5
Forensics/Physical Evidence
Hess 5-1
Introduction
• Evolution of law enforcement has benefited greatly
from forensic science
• Forensic science dates back to 1910 and the “exchange
principle” set forth by French criminologist Edmond
Locard
• Primary purpose of an investigation is to locate, identify
and preserve evidence
Hess 5-2
Definitions
CATEGORIES
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Testimonial
Documentary
Demonstrative
Physical
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Direct
Indirect
Hess 5-3
Investigative Equipment
OVERVIEW
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Selecting equipment
Equipment containers
Transporting equipment
Training in use
Hess 5-4
Crime Scene Integrity and
Contamination of Evidence
VALUE OF EVIDENCE
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Locard’s principle of exchange
Contamination
Integrity of evidence
Chain of evidence
Chain of custody
Hess 5-5
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
DISCOVERING OR RECOGNIZING EVIDENCE
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Legally seized
Properly processed
Use common sense
Standard of comparison
Forensic light sources
Hess 5-6
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
MARKING, IDENTIFYING AND COLLECTING EVIDENCE
• Mark, log, photograph
and collect all objects
• Requires judgment and care
• Avoid cross-contamination
• Make marks recognizable
and small as possible
Hess 5-7
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
PACKAGING AND PRESERVING EVIDENCE
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Package each item separately
Specific requirements for that type of evidence
Both plastic and paper forms of packaging available
Preserve evidence on immovable items at the scene
Transmittal letter
Hess 5-8
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
TRANSPORTING EVIDENCE
• Can deliver personally
• Use fastest method available
PROTECTING, STORING AND MANAGING EVIDENCE
• All evidence received is recorded in a register
• Some evidence requires more care than others
• Automated storage
Hess 5-9
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
EXHIBITING EVIDENCE IN COURT
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Identify the evidence as that found at the scene
Describe exactly where it was found
Establish its custody
Voluntarily explain any changes that have occurred
Hess 5-10
Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
FINAL DISPOSITION OF EVIDENCE
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Evidence must be legally disposed of
Returned to owner
Auctioned
Destroyed
Hess 5-11
Frequently Examined Evidence
FINGERPRINTS
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Latent fingerprints
Visible fingerprints
Plastic fingerprints
Dusting latent
fingerprints
• Lifting prints
Continued
Hess 5-12
Frequently Examined Evidence (Continued)
FINGERPRINTS
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Chemical development
Other methods
Elimination prints
Inked prints
Digital fingerprinting
Continued
Hess 5-13
Frequently Examined Evidence (Continued)
FINGERPRINTS
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Fingerprint patterns, analysis and identification
Usefulness of fingerprints
Admissibility in court
Other types of prints
Hess 5-14
Frequently Examined Evidence
VOICEPRINTS
• Graphic record made by a sound spectrograph
• No two voiceprints are alike
LANGUAGE ANALYSIS
• Psycholinguistics
• Excited utterances
Hess 5-15
Frequently Examined Evidence
HUMAN DNA PROFILING
• Identifying, collecting and preserving DNA evidence
• Moral and ethical issues
BLOOD AND OTHER BODY FLUIDS
• Luminol
• Bloodstains
• Spatter patterns
Hess 5-16
Frequently Examined Evidence
SCENT
• Every person has a unique scent
• Scent pads can be presented to a tracking dog
HAIRS AND FIBERS
• Examining hair
• Examining fibers
Hess 5-17
Frequently Examined Evidence
SHOE AND TIRE PRINTS AND IMPRESSIONS
• Can yield valuable investigative
data
BITE MARKS
• Photograph if too shallow
to cast
• Forensic odontologist
Hess 5-18
Frequently Examined Evidence
TOOLS AND TOOL MARKS
• Common tools are often used in crimes
• Tool mark is an impression left by a tool on a surface
FIREARMS AND AMMUNITION
• Many violent crimes are committed with a firearm
• Gunshot residue (GSR)
• Shooter ID kits
Hess 5-19
Frequently Examined Evidence
GLASS
• High-velocity versus low-velocity impacts
• Glass evidence reference
database
SOILS AND MINERALS
• Forensic geologists
• X-ray diffraction
• Microscope
Hess 5-20
Frequently Examined Evidence
SAFE INSULATION
• Few people normally come into contact with safe insulation
ROPES, STRINGS AND TAPES
• Laboratories have various comparison standards
• Fingerprints can occur on either side of a tape
Hess 5-21
Frequently Examined Evidence
DRUGS
• Put drugs in a bottle and attach label
• Solid drugs in a pillbox
WEAPONS OF MASS DESTRUCTION
• Designed to produce substantial damage
• Acronyms
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CBRNE
Hess 5-22
Frequently Examined Evidence
DOCUMENTS
• Do not touch documents with bare hands
• Identify cellophane/manila envelopes on the outside
DIGITAL EVIDENCE
• Pervasive nature of cell phones
• Digital forensic courses
Hess 5-23
Frequently Examined Evidence
LAUNDRY AND DRY-CLEANING MARKS
• Many launderers and dry cleaners use specific marking
systems
• Submit the entire garment to a laboratory
PAINT
• Paints are complex and are individual
• Use small boxes for submitting paint samples to the crime
lab
Hess 5-24
Frequently Examined Evidence
SKELETAL REMAINS
• Determine whether remains are animal or human
• Forensic anthropology
WOOD
• If found wet, keep it wet
• If found dry, keep it dry
Hess 5-25
Frequently Examined Evidence
OTHER TYPES OF EVIDENCE
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Learn to read product DNA
Manufacturer codes
Discarded items
Lab can provide collecting and packaging instructions
Hess 5-26
Evidence Handling and Infectious Disease
PRECAUTIONS
• Likely to encounter infectious body fluids
• Universal precautions
• Consider all body secretions as potential health
hazards
• Constantly be alert for sharp objects
• After processing, decontaminate the crime scene
Hess 5-27
Summary
• Criminal investigations rely heavily on various types of
evidence
• The more individual the evidence, the greater its value
• Mark or identify each item of evidence
• Package evidence properly
• Document custody of the evidence at every stage
• After a case is closed, evidence is returned to the
owner, auctioned or destroyed
Hess 5-28