Forensic Science
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Isolate and secure the scene
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Document the scene
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Search for evidence
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Collect and package the evidence while
maintaining the chain of custody
Submit the evidence for analysis
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A – Assess the crime scene and assist the injured
D – Detain the witness(es)
A – Arrest the perpetrator
P – Protect the crime scene
T – Take notes
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1)
2)
3)
Look for signs of life
Cordon off the scene (only allow
authorized personnel in)
Bodies should be certified as “dead” by a
medical examiner (ME) before being
moved
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A walkthrough is performed by the
crime scene investigator, the first officer,
and sometimes the lead detective
Record initial observations of who, what,
where, when, and how
Make a plan of action
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Record the crime scene and potential
evidence with
 Notes
 Photography
 Sketches
 Videography
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Record the following while at the crime scene
(details are the key):
Date
 Time
 Description of the location, weather, and
environmental conditions
 Description of the crime
 Location of the evidence relative to other key points
 Names of all people involved
 Any other relevant information

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Nothing should be moved until photographed
Take photos of the scene and the surroundings
Photograph entrances and exits
Take wide and close-up photos
Use various angles for each piece of evidence
Use a ruler to show size
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Draw a rough sketch at the scene (reconstruct it
better later)
Include
 Date, time, and location
 Scale
 Recovered items
 Important features
 Accurate distance measurements of objects
(from two fixed points)
 A legend for description of items
 A compass designating north
 Names of investigators, victims, and suspects
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Narrate the video
Be objective
Record from different perspectives
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Triangulation
 For each piece of evidence being recorded,
use two permanent objects as reference
points that are not likely to be moved
 The two reference points and the piece of
evidence form a triangle, hence the term
triangulation
 Whatever object you are measuring to or
from, use the same spot on the object every
time
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Rectangular Coordinates – Baseline
The simplest form of the rectangular coordinate
system
 Using a straight line between two known points,
items are measured along the line and then
measured perpendicular to the line
 Inside or outside of a house, this line can be a
straight wall
 Outdoor scenes can use a string or long measuring
tape as the reference or baseline
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Rectangular Coordinates – Grid
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Measure the distance of items from two
perpendicular baselines
This technique is particularly appropriate in a room
with perpendicular walls or outdoors with
perpendicular streets
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Polar Coordinates
 Measure both the distance and the
direction (angle) an object is from a
known reference point
 For example, 40 feet from the edge of
the house and 15 degrees east of north
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When searching a crime scene, wear the
following, if available, to minimize
contamination
Disposable gloves
 Masks
 Coveralls with a hood
 Slippers
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Depend on the size and the location of the
crime scene and the number of investigators
available
Stick to one pattern and one supervisor
Better to collect everything and not need it than
fail to collect something and need it later
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Spiral – may move inward or outward; best
used where there are no physical barriers
Grid – basically a double-line search; effective,
but time-consuming
Line (Strip) – best in large, outdoor scenes
Zone (Quadrant) – most effective in houses or
buildings; teams are assigned small zones for
searching
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Spiral
Strip or Line
Grid
Quadrant or Zone
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Physical evidence must be packaged and
collected before time and weather can alter it
Physical evidence – any object that can
establish that a crime has been committed or
links a crime and the victim or suspect
The Golden Hour – the window of opportunity
to collect time-sensitive information or
evidence
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Each item must be placed in a separate
container, and sealed and labeled
The most fragile evidence is collected and
packaged first
Different types of evidence require specific or
special collection and packaging techniques
The body is the property of the coroner or
medical examiner; collection of evidence on the
body is done by that department
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Containers such as vials, envelopes, plastic
bags, paper bags, canisters, and cardboard
boxes are good packaging devices
Most items should be placed in a primary
container and then in a secondary container
Trace evidence may be placed on a piece of
paper which is then folded in a “druggist fold”
and placed in a secondary container
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Containers should be sealed with tamper proof
tape, and dated and initialed
Each package should contain
Date, time, and location
 Case number
 Agency and collector’s name
 Victim’s name(s)
 Description of contents
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Never package two items from two different
sources or locations
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There must be a written record of all people
who have had possession of an item of
evidence, beginning at the time of collection
Every person who handled or examined the
evidence must be accounted for
Chain of Custody should include
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Date and time of transfer
Location of transfer
To/From names
Purpose of the transfer
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Crime Scene Investigators can submit evidence
for analysis to several national databases based
on the type of evidence
Examples include
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Automated Fingerprint Identification System (AFIS)
Integrated Automated Fingerprint Identification
System (IAFIS)
Combined DNA Index System (CODIS)
Integrated Ballistics Identification System (IBIS)
International Forensic Automotive Paint Data Query
(PDQ)
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0135158494, Saferstein, Richard. Forensic
Science: An Introduction. New Jersey: Pearson
Prentice Hall, 2008.
0757518257, Ball-Deslich, Barbara and John
Funkhouser. Forensic Science for High School.
2nd Edition. Kenall/Hunt, 2009.
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