Do now: Why do you think
pictures are so important for a
crime scene investigation?
THE CASE:
A man works with the police to identify criminals. His help is
invaluable even when he hasn’t witnessed a crime. Many
of the criminals he identifies are never caught, but the
police continue to ask the man for help. Coincidentally,
the man’s first name describes what he does to help the
police.
THE MYSTERY:
What is the man’s first name and what is his occupation?
CLUES:
The man’s name is not unusual.
The man is on the police payroll.
The man works with his hands and listens carefully to what
other people have to say.
The man is a trained professional, but also draws on
natural talent.
The man might share his name with the whole department.
The man has a 3 letter name.
First On The Scene
Aim: How does Locard’s Principle
Apply to the Crime Scene?
Ripples in a pond are like traces left at the scene of
a crime, they are produced as a consequence of an
action. They can be far-reaching and often
misleading. The scientist must interpret them
correctly for their true significance.
The exchange of materials
between two objects that come
into contact with one another.
Every Contact Leaves a Trace
“Every Contact Leaves a Trace.”
Sir Edmond Locard (1877-1966)
 Sherlock Holmes of France
 Created a very simple idea, that while
obvious to us now, was (and still is) quite
powerful to the science of Forensics.
 Being able to find the “trace” is only limited
by our abilities, knowledge, and degree of
refinement of techniques & equipment.

Forensic Science: can be defined as any
science as it relates to law. Because of this,
any science can be a “Forensic” science.
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Crime Scene Processing Protocol
Great care must be taken in order
not to contaminate the crime scene.
Locard’s Exchange principle state
that:
When a person has contact with
someone or something, that person
always leaves something behind. It
may be a hair or a skin cell, but
something is there.
Basics of crime scene processing:
1. INTERVIEW
2. EXAMINE
3. PHOTOGRAPH
4. SKETCH
5. PROCESS
Interview: The crime scene technician must
interview the first officer at the scene or the victim
to ascertain the "theory" of the case.
 Examine: Examine the scene to identify possible
items of evidentiary nature, identify point of entry
and point of exit, and getting the general layout of
the crime scene.
 Photograph: Photographing the crime scene to
record a pictorial view of what the scene looks like
and to record items of possible evidence. Crime
scene photographs are generally taken in two
categories, overall views and items of evidence.

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Sketch: A rough sketch is completed by the crime
scene technician to demonstrate the layout of the
crime scene or to identify the exact position of the
deceased victim or evidence within the crime scene.

Process: The crime scene technician will process
the crime scene for evidence, both physical and
testimonial evidence. It is the crime scene
technicians responsibility to identify, evaluate and
collect physical evidence from the crime scene for
further analysis by a crime laboratory.
Chain of evidence:
An unbroken chain of events regarding all evidence
collected. This includes the location of all evidence
from the time collected until submitted in court as well
as the person responsible for the evidence.
1. Do not move anything
2. Take measurements in order to complete a detailed, scaled
sketch. Include the scale on the drawing
3. Record the evidence you would like to see in the future.
You may label any evidence with a note card or record the
number if a note card is already in place.
4. Request additional photographs.
5. Be aware of EVERYTHING. Use your best skills of
observation.
Personnel Duties & Responsibilities
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Team Leader
 Assumes control at scene, conducts initial walkthrough, determines search patterns, designates
individuals for jobs
Photographer
Sketch Artist
Evidence Recorder & Custodian
 Maintain logs & proper packaging
Specialists
Forensic Anthropologist - Blood Spatter Analyst
Bomb Technician - Medical Examiner - Entomologist Odontologist - Engineer - Latent Print Examiner
- Ballistics - Arson - Impression Expert
Case Study
How can Physical Evidence
point investigators in the right
direction?
“Eyewitness” accounts may not
always be truthful!