This document provides guidance on processing crime scenes and securing physical evidence. Key steps include prioritizing medical aid, arresting perpetrators, securing the scene to preserve evidence, taking photographs to document locations and details, creating sketches of the scene, conducting systematic searches, carefully collecting and packaging all potential evidence while maintaining chain of custody, and considering legal and safety issues. Court decisions provide parameters around warrantless searches.

1. Processing the Crime Scene
Securing
Physical
Evidence
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2. What is Physical Evidence?
 Any and all objects that can:
 establish that a crime has been
committed
 link a crime and a victim
 link a crime and the perpetrator
 Selectivity is the key
 You can’t collect everything!

3. Priorities at the Crime Scene
 Obtain medical aid for those in need
 Arrest the perpetrator
 Secure the crime scene
 Exclude unauthorized personnel
 Remember Locard’s Exchange Principle!
 Determine crime scene boundaries
 Locate path of entry and exit

4. Photography
 Scene must be unaltered!
 If objects are removed,
positions changed, or items
added photos may be
inadmissable
 If items were moved (eg.
Securing a firearm) note it in
the report, do not put it back!
 Physical evidence must be
photographed to show:
 Position and location relative to
the scene
 Close-ups to show detail
 Scale to show size

5. Sketches
 Rough sketch records
 Dimensions of crime scene and
surroundings
 Location of each piece of physical
evidence
 Distances from two points
 Finished sketch
 Represents crime scene to the jury

6. Systematic Search Patterns
 Spiral search
 Grid method
 Strip of line search
 Quadrant or zone
search
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7. Evidence Collection
 Must collect all
possible carriers of
evidence
 Clothing
 Package each item
separately
 Cross-
contamination
 Sweepings
 Collect and package
each area
separately
 Fingernail scrapings

8. Evidence Collection
 Must collect all possible carriers of
evidence
 Head and pubic hairs
 For comparison purposes
 Blood or cheek swab for DNA
 Vaginal, anal and oral swabs
 For sex crimes
 Recovered bullets from the body
 Hand swabs for gunshot residue

9. Special Considerations for Arson
 Accelerants
 Volatile, evaporate
easily
 Collect ash and
debris for traces
 Store in airtight
paint cans with
vapor
concentrators

10. Standard/Reference Samples
 To show provenance  Substrate Controls
you need known  Samples of materials
reference samples to near where physical
compare to evidence was
 Hair deposited
 Fiber
 Want to show tests
for physical evidence
 Glass
don’t produce false
 DNA positives
 Blood  Untouched
wallboard in arson
 Background fabric
for blood test

11. Chain of Custody
 Key point of attack for the defense
 Every person who handled or
examined the evidence must be
accounted for
 Must be a written record of each hand-
off
 Each time container is opened a fresh
seal must be made and initialed

12. Safety Considerations
 AIDS and other infectious materials
 Double gloves, shoe covers, Tyvek suit
 Blood must be dried
 Biohazard bags
 Air-borne particulates and dust
 Particle mask, respirator, goggles, face shield
 Sharps and blood contamination
 No eating, drinking, smoking, putting on
make-up

13. Legal Considerations
 4th Amendment Rights
 Right against unreasonable search and
seizure
 Probable cause
 Description of place to be searched
 Description of persons or things to be
seized

14. Searching without a warrant
 Emergency circumstances
 Prevent loss or destruction of
evidence
 Search of person and property during
an arrest
 Search made with consent

15. Key Court Decisions
 Mincey v. Arizona
 Undercover cop killed trying to buy drugs
 Police search scene for four days without
obtaining a warrant
 Supreme Court throws out the evidence
found
 “No exigent circumstances”

16. Key Court Decisions
 Michigan v. Tyler
 Arson at a place of business
 Police search scene looking for arson but
leave scene unattended for several hours
 Return several times over next 4 weeks
to collect evidence without warrant
 Initial warrantless search is OK after fire
 Later searches thrown out