1. Chapter 5
Forensics/Physical Evidence
Hess 5-1

2. 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
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3. Definitions
CATEGORIES
• Testimonial
• Documentary
• Demonstrative
• Physical

Direct

Indirect
Hess 5-3

4. Investigative Equipment
OVERVIEW
• Selecting equipment
• Equipment containers
• Transporting equipment
• Training in use
Hess 5-4

5. Crime Scene Integrity and
Contamination of Evidence
VALUE OF EVIDENCE
• Locard’s principle of exchange
• Contamination
• Integrity of evidence
• Chain of evidence
• Chain of custody
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6. Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
DISCOVERING OR RECOGNIZING EVIDENCE
• Legally seized
• Properly processed
• Use common sense
• Standard of comparison
• Forensic light sources
Hess 5-6

7. 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

8. Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
PACKAGING AND PRESERVING EVIDENCE
• 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

9. 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

10. Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
EXHIBITING EVIDENCE IN COURT
• 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

11. Processing Evidence: Maintaining the Chain
of Custody from Discovery to Disposal
FINAL DISPOSITION OF EVIDENCE
• Evidence must be legally disposed of
• Returned to owner
• Auctioned
• Destroyed
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12. Frequently Examined Evidence
FINGERPRINTS
• Latent fingerprints
• Visible fingerprints
• Plastic fingerprints
• Dusting latent
fingerprints
• Lifting prints
Continued
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13. Frequently Examined Evidence (Continued)
FINGERPRINTS
• Chemical development
• Other methods
• Elimination prints
• Inked prints
• Digital fingerprinting
Continued
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14. Frequently Examined Evidence (Continued)
FINGERPRINTS
• Fingerprint patterns, analysis and identification
• Usefulness of fingerprints
• Admissibility in court
• Other types of prints
Hess 5-14

15. Frequently Examined Evidence
VOICEPRINTS
• Graphic record made by a sound spectrograph
• No two voiceprints are alike
LANGUAGE ANALYSIS
• Psycholinguistics
• Excited utterances
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16. 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
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17. 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
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18. 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

19. 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

20. 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

21. 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

22. 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
 CBRNE
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23. 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

24. 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
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25. 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

26. Frequently Examined Evidence
OTHER TYPES OF EVIDENCE
• Learn to read product DNA
• Manufacturer codes
• Discarded items
• Lab can provide collecting and packaging instructions
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27. 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

28. 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