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Crime Scene Investigation Basic Concepts
B.M.C. Durfee High School
Objectives • Understand and discuss what happens at a
crime scene
• Differentiate between various types of crime scenes
• Describe the steps in surveying a crime scene
• Identify different methods used in searches for physical evidence
What Happens At A Crime Scene
• The first responding officer will:
o Check the victim, call an ambulance if needed
o Secure the scene
o Apprehend any suspects
o Interview witnesses
o Report to superior officers about the incident
• One of the most important duties of the first responding officer is to secure and protect the integrity of the crime scene
o The evidence cannot be disturbed
What Happens At A Crime Scene…
• Next to arrive are the criminal investigators:
o Police detectives
o Crime scene investigators
• The investigators:
o Gather information
o Search for, document, collect, and preserve any evidence
o Conduct field tests and reconstruct the sequence of events
What Happens At A Crime Scene…
• The “chain of custody” of the evidence needs to be maintained
o If not, the evidence may not be admissible in court
Types of Crime Scenes • Can be classified where the crime was
committed and where the physical evidence has been found
o Primary scene
Where the criminal act occurred
o Secondary scene
Where the body was dumped
Anywhere evidence was found, such as a victims hair found at the suspects home
There can be several secondary scenes
Types of Crime Scenes… • Classify based on the type of crime
o Murder
o Robbery
• Classify based on the location of the crime
o Indoor
o Outdoor
• Classify based on the condition of the crime scene, (organized or disorganized)
• Classify based on the activity of the crime scene (active or passive)
• A crime scene can be as large as a whole building or as small as a broken fingernail
General Crime Scene Procedures
• The CSI team seeks to discover:
o The nature and patterns of the crime
o The different types of physical evidence left behind by the suspect and the victim
• They seek to answer:
o Who did it?
o How did they do it?
o Why did they do it?
o When and where was the crime committed?
Surveying The Crime Scene • The lead investigators and case officers
conduct a preliminary survey of the crime scene known as the “walk-through”
o Determine what type of crime scene it is
o Note the different types of evidence present at the crime scene. Note the weather conditions, open doors, light switches etc.
o Make a mental note of point of entry & exit
o Begin to mentally reconstruct the events that might of lead up to the crime
• During the walk-through the investigators try to answer the questions: Who? What? Where? How? And Why?
Documenting The Crime Scene • Documenting the crime scene serves three
purposes:
o To record & document the location of physical evidence
o To record & memorize the overall condition of the crime scene
o To allow investigators, forensic scientist, and attorneys to go back and “revisit the crime scene”
Methods Used To Document The Crime Scene
• Taking meticulous notes
o Need to write down the date and time of the investigation
oWhen they arrived and who was already there
o A description of the crime scene (weather, smells, location)
o A description of the victim: clothing, position, & wounds)
o Other observations: doors ajar windows broken, stains on the carpet etc.
Methods Used To Document The Crime Scene…
• Videotaping the crime scene
o Allows investigators to review the video evidence with advanced technology
o Should be done without any verbal commentary (except factual info like date and time etc.)
o The video should include a view of the crime scene from the point of view of the victim
Methods Used To Document The Crime Scene…
• Photographing the crime scene
o Still photography is important
o Do immediately after videotaping
o Get a visual record of crime scene and evidence
o Better to take too many photographs
o Something might become important later
Methods Used To Document The Crime Scene…
• Making a diagram of the crime scene
o Diagram or sketch the crime scene
o Show spatial relationship of objects
o Hard to get scale in photography
o How do rooms relate to each other?
Searching For Physical Evidence
• After careful documentation, begin detailed methodological search for physical evidence of a crime
• Physical evidence can tell many things about a crime: how a crime was committed, MO (mode of operation) of a particular criminal, tells how people, objects and places are linked to one another; helps identify unknown substances at a crime scene
• Provides investigative leads, help investigators reconstruct what happened during a crime
Searching For Physical Evidence…
• Physical evidence can link suspect and victim to one another and to the crime scenes
• Look for what is missing too! Like a wallet
• There are different patterns that can be used when searching for evidence (line, strip, grid, wheel, spiral (contracting or expanding)
Review • What happens at a crime
scene:
• Differentiate between various types of crime scenes:
• The first responding officer will:
o Check the victim
o Secure the scene
o Apprehend any suspects
o Interview witnesses
o Report to superior officers about the incident
• Next to arrive are the criminal investigators:
• Classify based where the evidence was found
• Classify based on the type of crime
• Classify based on the location of the crime
• Classify based on the condition of the crime scene
• Classify based on the activity of the crime scene
Review… • Describe the steps in
surveying a crime scene:
• Identify different methods used in searches for physical evidence:
• Lead investigators and case officers conduct a preliminary survey of the crime scene known as the “walk-through”
• They try to answer the questions: Who? What? Where? How? And Why?
• There are different patterns that can be used when searching for evidence:
o Line
o Strip
o Grid
o Wheel
o Spiral (contracting or expanding)
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