The Crime Scene
Forensic Science:
Fundamentals and
Investigation
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Bertino
The Seven S’s of Crime Scene
Investigation
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Secure the scene
Separate the witnesses
Scan the scene
Seeing the scene
Sketch the scene
Search for evidence
Secure the collected evidence
Forensic Science: Fundamentals & Investigations, Chapter 2
First Responding officer
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First on scene is responsible for:
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Acquiring medical assistance for injured
Detaining any suspects and witness
Secure the scene to greatest extent possible
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Call for any needed personnel
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Look for points of entry and exit
backup or forensic investigator
Forensic Science: Fundamentals & Investigations, Chapter 2
Securing the scene
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A perimeter needs to be set
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Preserves and protects scene and evidence
May be necessary to set up multi level
perimeters
Investigators should never do anything that
might alter the crime scene including
smoking, eating, drinking, or littering.
Forensic Science: Fundamentals & Investigations, Chapter 2
Multi Level Containment
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Forensic Science: Fundamentals & Investigations, Chapter 2
The Crime Scene
Investigation Team
Who is at the crime scene?
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Police and
District attorney (possibly)
Crime scene investigators
Medical examiners
Detectives
Specialists
Forensic Science: Fundamentals & Investigations, Chapter 2
Searching the Scene
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The search for physical evidence at a crime
scene must be thorough and systematic.
The search pattern selected will normally
depend on the size and locale of the scene
and the number of collectors participating in
the search.
Before search begins area should be
surveyed
Forensic Science: Fundamentals & Investigations, Chapter 2
Crime-Scene Search Patterns
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Forensic Science: Fundamentals & Investigations, Chapter 2
Searching the crime scene
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Vehicle Searches
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Investigators search interior and exterior of
vehicle.
The vehicle may be searched at the crime scene
or at the police department or crime laboratory
garage
Forensic Science: Fundamentals & Investigations, Chapter 2
Recording the Crime Scene
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Photography, sketches, and notes are the
three methods for crime-scene recording.
Forensic Science: Fundamentals & Investigations, Chapter 2
Crime Scene Notes
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The crime scene notes should begin with:
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The identity of person who contacted the
investigator
Time of contact and arrival at the crime scene
Preliminary case information
Personnel present on arrival and those being
contacted
Forensic Science: Fundamentals & Investigations, Chapter 2
Crime Notes…
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Notes contain a personnel log, all
observations made by the investigator,
and the time observations were made.
Notes are taken in a uniform layout,
concurrently as the observations are
made.
Notes are written in a bound notebook
in blue or black ink
Forensic Science: Fundamentals & Investigations, Chapter 2
Crime Scene Photography
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Crime scene photographs should record the
area in which the crime actually took place
and all adjacent areas where important acts
occurred.
The most important prerequisite for
photographing a crime scene is for it to be in
unaltered condition
Forensic Science: Fundamentals & Investigations, Chapter 2
Crime Scene Photography
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Required Photographs
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Overview photo
Medium range photo
Close-up photo
Close-up photo with scale
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Crime Scene Sketch
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Clearly show the layout of a crime scene
Illustrate the relationship in space of all significant
items and features
Clarify objects and features already described in
notes or shown in photographs
Show measurements over long distances
and topography of outdoor scenes
Depict possible paths of entry, exit, and
movement through the scene
Forensic Science: Fundamentals & Investigations, Chapter 2
Rough Sketch
• A rough sketch is created at the crime scene
and contains an accurate depiction of the
dimensions of the scene and shows the
location of all pertinent objects and features.
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Forensic Science: Fundamentals & Investigations, Chapter 2
Crime-Scene Sketch Form
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Forensic Science: Fundamentals & Investigations, Chapter 2
Types of Evidence
Direct evidence
Testimony by a
witness about what
that witness saw,
heard, or did
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Forensic Science: Fundamentals & Investigations, Chapter 2
Types of Evidence
Circumstantial evidence
•
also called Indirect
•
trace evidence
Physical evidence
•
e.g., fingerprints
Biological evidence
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Forensic Science: Fundamentals & Investigations, Chapter 2
e.g., blood or hairs
Collecting Evidence
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Often, many items of evidence are clearly
visible but others may be detected only
through examination at the crime laboratory.
Forensic Science: Fundamentals & Investigations, Chapter 2
Collection…
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Investigators handle and process physical
evidence in a way that prevents changes to
the evidence through contamination,
breakage, evaporation, accidental scratching
or bending, or through improper or careless
packaging.
Forensic Science: Fundamentals & Investigations, Chapter 2
Types of Evidence
Explain why this would be or
would not be trace evidence
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Forensic Science: Fundamentals & Investigations, Chapter 2
Packaging the evidence
Crease a clean paper and
place evidence in the X
position
2. Fold in the left and right sides,
and then fold in the top and
bottom
3. Put the bindle into a plastic or
paper evidence bag affixing a
seal over the opening
4. Write your name on the seal
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Evidence ID Forms
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Chain of Custody
Maintaining a chain of custody log is essential to
present credible evidence in court
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Forensic Science: Fundamentals & Investigations, Chapter 2
Chain of Custody (cont’d.)
1. Bag the evidence
Add identification
Seal it
Sign it across the sealed edge
2. Sign over to a lab technician
Open bag on non-sealed edge
3. Return items to the evidence bag
Seal evidence bag in another
bag
Sign the evidence log
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Forensic Science: Fundamentals & Investigations, Chapter 2
Analyze the Evidence
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Facts result from collected evidence
processed by the forensic lab
Lead detective aims to see how facts fit into
the crime scenario
Forensic Science: Fundamentals & Investigations, Chapter 2
Analyze the Evidence
Lab results can:
o Show reliability of witness accounts
o Establish the identity of suspects or victims
o Show suspects to be innocent or link them
with a scene or victim
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Forensic Science: Fundamentals & Investigations, Chapter 2
Crime Scene Reconstruction
Crime scene reconstruction involves:
o Forming a hypothesis of the sequence of
events
o From before the crime was committed
through its commission
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Forensic Science: Fundamentals & Investigations, Chapter 2
Staged Crime Scenes
When lab results don’t match up with the
testimony of witnesses
Common examples:
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Staging a fire—to cover bankruptcy
Staging a suicide—to cover a murder
Staging a burglary—to collect insurance
money
Forensic Science: Fundamentals & Investigations, Chapter 2
Staged Crime Scenes
Was the crime scene staged?
Consider:
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Does the type of wound match the weapon?
Could the wound be easily self-inflicted?
What were the mood and actions of the victim
before the event?
What were the mood and actions of the suspect
before the event?
Forensic Science: Fundamentals & Investigations, Chapter 2
. . . . . . . . . . . . . . Summary . . . .
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Locard’s exchange principle:
• Contact between people and objects can
transfer material that can determine the nature
and duration of the transfer
Evidence can be direct or indirect
• Physical or biological traces
A crime scene investigation team consists of
police, detectives, crime scene investigators,
medical investigators, and specialists.
Forensic Science: Fundamentals & Investigations, Chapter 2
. . . . . . . . . . . . . . . . . Summary
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Investigations consist of recognizing, documenting,
and collecting evidence.
First responding officers identify the extent of the
crime scene, secure it, and segregate witnesses.
Crime scene investigators document the crime
scene.
Evidence is collected, packaged, and labeled.
The evidence is analyzed and interpreted to fit the
crime scenario.
Forensic Science: Fundamentals & Investigations, Chapter 2