forensic science: fundamentals & investigations, chapter 2 1 what makes a good observer?...

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?


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


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


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


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


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


Types of EvidenceTypes of Evidence

Explain why this would be or would not be trace evidence


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


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


1. Securing the Scene

o First Responder- policepolice• Is it safe?• Preserve any

evidence (prevent transfer, loss or contamination)


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


#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)


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


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)


6. Searching for Evidence

o Walk the grido Vacuums, Lights, Forceps


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


Closure

o Tomorrow’s Crime Scene• Clothing• Observation


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


Evidence ID Forms


Chain of Custody

Maintaining a chain of custody log is essential to present credible evidence in court


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


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


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


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


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


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?


. . . . . . . . . . . . . . . . . . . . . . . . . . . . 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.


. . . . . . . . . . . . . . . . . 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.

forensic science: fundamentals & investigations, chapter 2 1 what makes a good observer?...

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