The Crime Scene
Chapter Two
Forensic Science
Physical Evidence
• Any object that can establish a crime
has been committed or can link a crime
and its victim and its perpetrator
• You must be able to recognize and
properly preserve physical evidence at
a crime scene
The Crime Scene
• Step 1: Secure and isolate the crime
scene to prevent contamination,
destruction of evidence
• Step 2: Record the scene – take lots of
notes
• Step 3: Photograph or video the scene before it is disturbed – close-up and
distance shots (p46)
• Step 4: Sketch the crime scene - rough
sketch first; then finished sketch
incorporating the notes (p 47-8)
Value of Physical Evidence
• Physical evidence is used to
• Show that a suspect where they had no right
to be.
• Establish a suspect's presence at the crime
scene.
• Establish probable cause (motive) for the
event.
• Establish proof beyond a reasonable doubt of
YOUR version of the event.
Value of Physical Evidence
Human factor of physical evidence:
•Physical evidence "can't lie, quit, die, forget, or
get fired”
•Testimonial evidence may change or source
may become "nonexistent' between original and
court version
Physical properties of physical evidence:
•Cannot change
•But the identification or interpretation of the
evidence can change or be incorrect
"Golden Rule" of Crime Scene Management
"Never touch, change, or alter anything until it has been
documented, identified, measured, and photographed . . .
when a body or article has been moved, it can never be
restored to its original position.”
Exceptions to the Golden Rule:
(1) If a weapon could be used to cause harm/death to
someone at the scene.
(2) If the potential exists for an item/evidence to be lost,
contaminated or destroyed (weather, traffic, etc)
Transient evidence is that type of short-lived
evidence subject to damage or destruction by
exposure to the elements.
Evidence which changes with the passage of time.
Crime Scene Search
FIRST OFFICER on the scene MUST
• Secure and protect the scene.
･To "secure" is to close access
･To "protect" is to deny access.
• Identify, remove, and separate the witnesses
from the scene.
Other actions may include:
• Perform preliminary survey of the scene.
• Establish control of the scene
• Determine extent of search
Crime Scene Management
Crime Scene Investigators
• Develop preliminary theory.
• Identify physical evidence.
• Begin documentation.
• Record narrative of the scene.
Notes - keep forever.
Audiotape - use new tape, maintain tape in
chain of custody as evidence, transcribe.
Videotape (sight/sound) - "hears all, sees
all," disconnect sound.
Photographic record of the
scene.
Record the scene with
photographs and video if
available,
Photograph the scene
in progressive sequence
Overview (entire scene)
ending with close-up of
each item.
First without measurement
scale, then with.
• Finished sketch
SKETCHING THE CRIME
SCENE
• Draw a Rough Sketch of the scene.
• Document the relationship physical
evidence items, including locations and
distances from FIXED OBJECTS.
• Experience helps to develop ability to
identify the most useful items at the
scene.
CRIME SCENE SEARCH
General Rules:
•Detailed search of scene, leave "No stone
unturned”
•Record, collect, mark, and preserve evidence.
•Be aware that collecting one type of evidence
may destroy another type.
•Choose the appropriate search pattern.
•Perform final survey of the scene and doublecheck documentation and thoroughness of
search.
Inward Spiral Search Pattern
• The inward spiral
search:
• The CSI starts at the
perimeter of the scene
and works toward the
center.
• Spiral patterns are a
good method to use
when there is only one
CSI at the scene.
Outward Spiral Search
• The outward spiral
search:
• The CSI starts at the
center of scene (or
at the body) and
works outward.
Parallel Search
• The parallel search:
• All of the members
of the CSI team form
a line.
• They walk in a
straight line, at the
same speed, from
one end of crime
scene to the other.
Grid Search Pattern
• The grid search:
• A grid search is
simply two parallel
searches, offset by
90 degrees,
performed one after
the other.
Zone Search Pattern
• The zone search:
• In a zone search, the
CSI in charge divides
the crime scene into
sectors, and each team
member takes one
sector.
• Team members may
then switch sectors and
search again to ensure
complete coverage.
Are the doors and windows locked or unlocked? Open or shut? Are there signs of forced entry, such as
tool marks or broken locks
Is the house in good order? If not, does it look like there was a struggle or was the victim just messy?
Is there mail lying around? Has it been opened?
Is the kitchen in good order? Is there any partially eaten food? Is the table set? If so, for how many
people?
Are there signs of a party, such as empty glasses or bottles or full ashtrays?r full ashtrays
If there are full ashtrays, what brands of cigarettes present? Are there any lipstick or teeth marks on
the butts?
Is there anything that seems out of place? A glass with lipstick marks in a man's apartment, or the
toilet seat up in a woman's apartment? Is there a couch blocking a doorway?
Is there trash in the trash cans? Is there anything out of the ordinary in the trash? Is the trash in the
right chronological order according to dates on mail and other papers? If not, someone might have
been looking for something in the victim's trash.
Do the clocks show the right time?
Are the bathroom towels wet? Are the bathroom towels missing? Are there any signs of a cleanup?
If the crime is a shooting, how many shots were fired? The CSI will try to locate the gun, each
bullet, each shell casing and each bullet hole.
If the crime is a stabbing, is a knife obviously missing from victim's kitchen? If so, the crime may
not have been premeditated.
Are there any shoe prints on tile, wood or linoleum floors or in the area immediately outside the
building?
Are there any tire marks in the driveway or in the area around the building?
Is there any blood splatter on floors, walls or ceilings?lls or ceilings
Procedures for Evidence Collection
• Physical evidence must be
collected INDIVIDUALLY
• Packaging is VERY
important:
• Ashes – clean paint can
• Bloodstained items (dry)paper bag
• Bloodstain items (wet)paper bag
• Dirt – manila envelope
• MUST label each item
• Items MUST be sealed
• Chain of Custody
Evidence Collection
• Item should be kept • Bloodstains and other
biological evidence
in as original
should be collected in
condition as
paper bags, manilla
possible
envelopes or druggist
folds to prevent the
• Evidence should be
growth of mold.
submitted as intact
• Stained clothing should
as possible
be air dried before
• Each item collected
wrapping
should be bagged
• Charred debris from a
separately
fire must be placed in
airtight containers
Chain of Custody
• All evidence MUST be
sealed at the time of
collection
• All evidence has a
complete list of anyone
who comes in contact with
the item
Medical Examiner/Forensic
Pathologist
Answers basic questions:
• Who was the victim?
• What injuries are
present?
• When did the injuries
occur?
• Why and how were the
injures produced?
Performs autopsy to
establish cause of death
Estimates TOD (time of
death)
Post Mortem Terms
• Rigor mortis muscles relax then
stiffen occurs between
24-36 hours (“stiff”)
• Livor mortis - blood
pools closest to the
ground when the heart
stops beating leaving
• Algor mortis - body
temperature drops at a
rate of 1-1/2 degrees F
per hour until it reaches
ambient temperature
Forensic Anthropologist
• Identification and
examination of
human skeletal
remains
• Bones can reveal
sex, approximate
age, race,and
skeletal injury
• Create facial
reconstructions
Ex: Case Study
(pages 60-1)
Forensic Entomologist
• Examines insects
and their relation to
criminal
investigation
• Blowflies, bottle
flies, house flies, lay
eggs, which hatch
into maggots, then
grow into adult flies
Ex: The number of eggs,
maggots &adult flies can
determine the approximate
TOD and length of
decomposition time.
EDMUND LOCARD
France’s “Father of
Forensics” in Lyon,
France.
Dr. Locard was a
medical examiner
during WWI.
Believed that every
contact produced
an exchange of
physical material.
• Locard’s Exchange
Principal
• Any action of an
individual, and
obviously the violent
action constituting a
crime, cannot occur
without leaving a trace.”