Post on 02-Jan-2016
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Forensic Science: Fundamentals & Investigations, Chapter 2 1
What Makes a Good Observer?
1. Describe how I moved the first 3 objects in detail.
2. How many steps did I take to get from the desk to the back counter?
3. What color were my shoes
4. What was in my left hand as I walked from the back of the room to the front?
5. How was my hair when you first walked into the room?
6. What is missing from the back of the room?
7. What was the pattern of the eraser blocks on my desk at the start?
8. What was the pattern of the eraser blocks on my desk now (look up)?
9. What are the 4 ways to be a good observer?
Forensic Science: Fundamentals & Investigations, Chapter 2 2
Chapter 2 Crime Scene Investigation and Evidence Collection Objectives:Objectives:
1. Summarize Locard’s exchange principle
2. Identify four examples of trace evidence
3. Distinguish between direct and circumstantial evidence
4. Identify the methods by which a crime scene is documented
Forensic Science: Fundamentals & Investigations, Chapter 2 3
Principle of ExchangePrinciple of Exchange
Established by Dr. Edmond Established by Dr. Edmond LocardLocard, , When a person comes in contact with When a person comes in contact with
an object or another person, aan object or another person, a cross-cross-transfertransfer of physical material can of physical material can occuroccur
Study of the material canStudy of the material can determine determine the nature and duration of the the nature and duration of the transfer transfer
Forensic Science: Fundamentals & Investigations, Chapter 2 4
What could be Transferred?
1. Hair (eyelash)
2. Saliva
3. Skin
4. Blood
5. Fibers
6. Fluids
7. Nails
8. Tooth
9. Jewelry
10. Makeup
11. Scent
12.MANY MORE
Forensic Science: Fundamentals & Investigations, Chapter 2 5
Types of Types of Evidence Evidence
Direct evidence
Testimony by a witness Testimony by a witness about what that about what that
witness saw, heard, or witness saw, heard, or did did
Forensic Science: Fundamentals & Investigations, Chapter 2 6
Types of Types of EvidenceEvidence
CircumstantialCircumstantial evidenceevidence
• also calledalso called IndirectIndirect
• trace evidencetrace evidence
PhysicalPhysical evidence evidence
• e.g., fingerprintse.g., fingerprints
BiologicalBiological evidenceevidence
• e.g., blood or hairse.g., blood or hairs
Forensic Science: Fundamentals & Investigations, Chapter 2 7
Types of EvidenceTypes of Evidence
Explain why this would be or would not be trace evidence
Forensic Science: Fundamentals & Investigations, Chapter 2 8
The Crime Scene The Crime Scene Investigation Team Investigation Team
Who is at the crime scene?
o Police and o District attorney (possibly)o Crime scene investigatorso Medical examinerso Detectiveso Specialists
Forensic Science: Fundamentals & Investigations, Chapter 2 9
The Seven The Seven SS’s of ’s of Crime Scene Crime Scene InvestigationInvestigation
1.1. Secure the sceneSecure the scene2.2. Separate the witnessesSeparate the witnesses3.3. Scan the sceneScan the scene4.4. Seeing the sceneSeeing the scene5.5. Sketch the scene Sketch the scene 6.6. Search for evidenceSearch for evidence7.7. Secure the collected evidenceSecure the collected evidence
Forensic Science: Fundamentals & Investigations, Chapter 2 10
1. Securing the Scene
o First Responder- policepolice• Is it safe?• Preserve any
evidence (prevent transfer, loss or contamination)
Forensic Science: Fundamentals & Investigations, Chapter 2 11
2. Separating the Witnesses
o DO NOT TALK TO EACHOTHERo Asked questions about the crime
• Who called it in• Who did you see• What did you see• Can you identify persons• Where were you
Forensic Science: Fundamentals & Investigations, Chapter 2 12
#3- Scanning the Scene
o Where do you take pictures from?o Primary Vs Secondary Crime Scene
• Primary (Robbery at bank)• Secondary (Suspect’s house)
Forensic Science: Fundamentals & Investigations, Chapter 2 13
4. Seeing the Scene
o All photos taken (with and without rulers)
o Triangulation of stationary objects included in photos• Various angles and
distances• Close ups
Forensic Science: Fundamentals & Investigations, Chapter 2 14
5. Sketching the Scene
o Note all positions, landmarks, Note all positions, landmarks, doorways, windows, trees (outdoors)doorways, windows, trees (outdoors)
o Note all objects (placement is key)
Forensic Science: Fundamentals & Investigations, Chapter 2 15
6. Searching for Evidence
o Walk the grido Vacuums, Lights, Forceps
Forensic Science: Fundamentals & Investigations, Chapter 2 16
7. Securing and Collecting Evidence
o Proper Packaging, sealing, labels• Liquids/Arson airtight & unbreakable container• Biological breathable so it can dry (prevent
mold)
o Paper Bindleso Chain of Custody
• Who did what and when
Forensic Science: Fundamentals & Investigations, Chapter 2 17
Closure
o Tomorrow’s Crime Scene• Clothing• Observation
Forensic Science: Fundamentals & Investigations, Chapter 2 18
Packaging the evidence
1. 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
Forensic Science: Fundamentals & Investigations, Chapter 2 19
Evidence ID Forms
Forensic Science: Fundamentals & Investigations, Chapter 2 20
Chain of Custody
Maintaining a chain of custody log is essential to present credible evidence in court
Forensic Science: Fundamentals & Investigations, Chapter 2 21
Chain of Custody (cont’d.)
1. Bag the evidenceAdd identification Seal itSign it across the sealed edge
2. Sign over to a lab technician Open bag on non-sealed edge
3. Return items to the evidence bagSeal evidence bag in another bagSign the evidence log
Forensic Science: Fundamentals & Investigations, Chapter 2 22
Analyze the EvidenceAnalyze the Evidence
o Facts result from collected evidence processed by the forensic lab
o Lead detective aims to see how facts fit into the crime scenario
Forensic Science: Fundamentals & Investigations, Chapter 2 23
Analyze the EvidenceAnalyze the Evidence
Lab results can: o Show reliability of witness accountso Establish the identity of suspects or victimso Show suspects to be innocent or link them
with a scene or victim
Forensic Science: Fundamentals & Investigations, Chapter 2 24
Crime Scene Reconstruction 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
Forensic Science: Fundamentals & Investigations, Chapter 2 25
Staged Crime Scenes Staged Crime Scenes
When lab results don’t match up with the testimony of witnesses
Common examples:
o Staging a fire—to cover bankruptcyo Staging a suicide—to cover a murdero Staging a burglary—to collect insurance
money
Forensic Science: Fundamentals & Investigations, Chapter 2 26
Staged Crime ScenesStaged Crime Scenes
Was the crime scene staged? Consider:
o Does the type of wound match the weapon?o Could the wound be easily self-inflicted? o What were the mood and actions of the victim
before the event?o What were the mood and actions of the suspect
before the event?
Forensic Science: Fundamentals & Investigations, Chapter 2 27
. . . . . . . . . . . . . . . . . . . . . . . . . . . . SummarySummary . . . . . . . .
o Locard’s exchange principle: • Contact between people and objects can
transfer material that can determine the nature and duration of the transfer
o Evidence can be direct or indirect • Physical or biological traces
o A crime scene investigation team consists of police, detectives, crime scene investigators, medical investigators, and specialists.
Forensic Science: Fundamentals & Investigations, Chapter 2 28
. . . . . . . . . . . . . . . . . Summary. . . . . . . . . . . . . . . . . Summary
o Investigations consist of recognizing, documenting, and collecting evidence.
o First responding officers identify the extent of the crime scene, secure it, and segregate witnesses.
o Crime scene investigators document the crime scene.
o Evidence is collected, packaged, and labeled.o The evidence is analyzed and interpreted to fit the
crime scenario.