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

Crime Scene Evidence Video

Crime Scene Evidence

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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