Chapter 10: Crime Scene Investigation

Textbook page 167

I. Introduction

A. Forensic science begins at the crime scene.

B. Four steps of Crime Scene Investigation (CSI)

1. Recognition—scene survey, documentation, collection

2. Identification—comparison testing

3. Individualization—evaluation, interpretation

4. Reconstruction—reporting and presentation

C. A main goal of CSI is to successfully identify and preserve physical evidence.

1. Two general types of evidence: direct and physical

a. Direct/testimonial = evidence in the form of a statement made under oath.(go to eyewitness slides)

b. Physical evidence = any and all objects and materials that are relevant in a crime (examples: drugs, toxic substances, paints, gunshot residues, firearms and ammunition, impressions, petroleum products, blood, fibers, glass, hair, body fluids, fingerprints, etc.)

I. Introduction (cont.)

VS.

Direct/testimonial evidence extension activity

• Note: The next 10 slides came from The Science Spot website

• http://sciencespot.net/Pages/classforsci.html#crimescene

Testimonial evidence includes oral or written statements given to police as well as testimony in court by people who witnessed an event.

Eyewitness accounts can be a useful tool in helping investigators with analyzing a crime scene, but are not viewed to be highly reliable. In addition, eyewitness identifications (right or wrong) can have a big influence on the outcome of an investigation or trial.

People are likely to view the same scene in different ways depending on their positions, line of sight, familiarity with the area, and other factors that can interfere with a person’s ability to remember details.

What is testimonial evidence?

Directions:

You will have 30 seconds to view the next screen.

Try to memorize all 20 items you see!

You are NOT allowed to write anything down

You CANNOT talk to anyone else.

Memory Challenge

Neuroscience for Kids - http://faculty.washington.edu/chudler/puzmatch1.html

Items to remember ...

What do you remember?You have 2 minutes to list as many of the items as you can!

How did you do?

All 20 – Awesome

15-19 – Great

10-14 – Pretty swell

5-9 – Could be better

4 or Less – Wake up

According to The Innocence Project (2008) "Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in more than 75% of convictions overturned through DNA testing." Still, the criminal justice system profoundly relies on eyewitness identification and testimony for investigating and prosecuting crimes (Wells & Olson, 2003).

Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts

Did you know?

What factors affect a person’s memory and their ability to identify a suspect?

• Age may play a role in the accuracy of an eyewitness’ statement or identification of a suspect. Studies have shown that when a lineup contains the actual culprit, both young children and elderly perform well, but when the lineup does not contain the culprit there is a higher rate of mistaken identifications.

• The race of the witness may also play a role. The Cross Race Effect (CRE) is a phenomenon in which people are better at recognizing faces of their own race rather than those of other races.

• The use of drugs can alter a person’s ability to recall the events of a crime even after they are no longer under the influence.

• A person’s memory of an event can be influenced by other witnesses, investigators, and/or the media. Investigators use open-ended questioning and follow procedures for conducting line-ups to limit their influence on a witness’ memory of an event or identification of a suspect.

Witness Factors

Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts

• A crime that is extremely traumatic for an eyewitness may affect his/her recall of the event. For example, a witness confronted with a weapon tends to focus on the weapon rather than the perpetrator’s face.

• Someone who is able to focus on a perpetrator's face for a minute or longer will tend to have a more accurate memory than someone who saw the person for only a few seconds.

• Studies have shown that faces that are either highly attractive, highly unattractive, or distinctive are more likely to be accurately recognized. Simple disguises, such as hats or sunglasses, can interfere with accurate eyewitness identification. However, body piercings and tattoos increases the likelihood of an accurate identification.

• The time of day in which the crime occurred as well as a person’s view of the scene may affect what a he/she is able to see. In addition, a person who is familiar with the area in which the crime took place, may have a better recall of the positions of the victims or suspects.

Crime Scene & Suspect Factors

Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts

Crime Scene Challenge

• Now that your eyes and brain are warmed up, let’s test your observation skills a bit more.

• You will have 2 minutes to study the photograph of a crime scene on the next slide.

• Try to pay attention to details as you will be asked 10 questions about the crime scene!

• You are not allowed to write anything down until after the time is up.

• Ready?

Answer each question below.

1. What color coffee mug was in the picture? Blue Red Yellow  2. When was the deadline? Yesterday Today Tomorrow 3. What time was on the clock on the wall? 10:40 11:05 1:55  4. How many sticky notes were on the whiteboard? Four Six Eight 5. Which of the following was NOT in the picture? Stapler Trash Can Printer 6. What was the name on the plaque on the desk? Bill Brian Carl  7. What color was the victim's shirt? Black Blue Red 8. How many plants were in the picture? None One Two

9. What was the color of the marker in the desk drawer? Red Blue Green

10. Where was the book in the picture? On a box In the trash can Under the body

Source: http://forensics.rice.edu/html/picture_begin.html

2. Use of physical evidence

a. Prove that a crime has been committed

b. Corroborate testimony

c. Link a suspect with a victim or with a crime scene

d. Establish the identity of persons associated with a crime

e. Allow reconstruction of events of a crime

II. Defining a crime sceneA. Crime scene are diverse and unique . . .

no two scenes are exactly the same

http://www.exposay.com/celebrity-photos/crime-scene-4th-shooting-in-hacney-within-2-weeks-1uvxtj.jpg

http://www.srpublications.com/criminology/item/D/images_D/crime_scene_reconstruction.jpg

B. Classification of crime scenes can be based on . . .

1.location

a.primary: site of original or first criminal activity

b.secondary: any subsequent sites of criminal activity

2.size

a.macroscopic crime scene: composed of many crime scenes (overall area)

b.microscopic crime scene: focused on specific types of physical evidence found at the macroscopic crime scene

II. Defining a crime scene (cont.)

3. type of crime committeda. homicideb. robberyc. sexual assaultd. etc.

4. condition of the crime scenea. organized b. disorganized

6. physical location of crime scenea. indoorsb. outdoorsc. vehicled. etc.

7. others

Note: Each crime scene can be a combination of these classifications. Also as an

investigation proceeds, the definition of the crime scene can be constantly modified.

III. General procedures for CSI (recognition step)

A. Secure and protect the crime scene

1. First responding officer

a. critical role

b. responsibilities include:

i. assist the victim

ii. search for and arrest suspects if possible

iii. detain all witnesses

iv. protect and secure the scene

v. note and communicate to investigators all movements and alterations made to the scene

http://www.fundraw.com/clipart/clip-art/00000898/Police-Officer/

2. Establish crime scene securitya. Why? Locard’s Principleb. Multi-level approach

III. General procedures for CSI A. Secure and protect the crime scene (cont.)

James, S.H., & Nordby, J.J. (2005). Forensic Science: An Introduction to Scientific and Investigative Techniques. 2nd Edition. New York: Taylor & Francis. Pg. 171.

http://shine4ever.files.wordpress.com/2009/08/crime-scene-tape-police-lights.jpg

B. Survey the scene

1. “Walk-through”

2. Note: transient (temporary) or conditional (the result of an action) evidence, points of entry and exit, and initial observations

C. Documenting a crime scene

Four main components = notes, photography, videotape, sketch

(see concept map or web for explanations)

III. General procedures for CSI (cont.)

D. Crime Scene Searches

1. Preliminary searcha. done once the scene is secured

b. purpose = note obvious evidence

2. Post-documentation searcha. intensive search for less obvious/overlook

evidence

b. completed before collection and packaging of evidence

c. evidence found must be documented before collection

III. General procedures for CSI (cont.)

3. Search methods/patterns

a. Purpose = provide systematic search so no evidence missed

b. Organized = everyone on same page and stress no touching or altering evidence (just mark they are there)

c. Six most common search patterns

1. Link

2. Line or Strip

3. Grid

4. Wheel or Ray

5. Spiral

6. Zone

III. General procedures for CSI D. Crime Scene Searches (cont.)

Crime scene search patterns

1. Link

2. Line or strip

3. Grid

4. Wheel or Ray

5. Spiral

6. Zone

1 2

3 4

E. Collection of Evidence

1. Done AFTER crime scene documentation and intensive search for evidence

2. Evidence collector = one person given this job

--Why?

To ensure evidence collected, packaged, marked,

sealed, and preserved in CONSISTENT manner

3. Order of collection

a. no set order

b. depends on nature of the evidence

--example: transient, fragile, or easily lost evidence collected first

4. IMPORTANT: if any new evidence discovered, must first DOCUMENT it before collecting

III. General procedures for CSI (cont.)

5. General collection guidelines

a. Most items packaged in primary container, then placed inside secondary container

b. Outer container

i. completely sealed at time of collection with tamper-resistant tape

ii. marked with: items contained; ID of collector; time, date, and location of collection

c. Each item packaged SEPARATELY to prevent

cross-contamination

III. General procedures for CSI E. Collection of Evidence (cont.)

http://www.fbi.gov/publications/leb/2006/april2006/page25.jpg

6. Ways to package different categories of evidence

a. Biological material

--packaged in a dry paper bag (NOT plastic)

b. Trace evidence (hairs, fibers, etc.)

--packaged in small envelops or tins

--Druggist’s folds used as primary container =

pieces of paper folded around items to hold trace

evidence in place before placed in outer container

c. Fingerprints

--lifted fingerprints are attached to an index card

d. Arson debris

-- packaged in old paint cans or mason jars (sealed

glass jar)

e. Castings

--packaged in a box with cushioning

III. General procedures for CSI E. Collection of Evidence (cont.)

http://www.shenet.org/High/hsacaddept/science/jstdenis/Forensic%20Science/PowerPoint%20Presentation.swf

F. Crime Scene Reconstruction1. The process of analyzing data to ultimately

develop a theory of the crime

2. Stages involved (see diagram and explanations on page 180 of textbook):a. Data collection

b. Conjecture

c. Hypothesis formation

d. Testing

e. Theory formation

III. General procedures for CSI (cont.)

Crime scene sketching directions

Crime scene sketching example

Crime Scene sketchingmethods

Crime Scene SketchingCS sketching is the final step in CS documentationProvides for dimensional relationships

2 views1. Bird’s eye view (top-down/overhead . . .most common)2. Elevation view (side-on)

2 types3. Rough sketch—completed at scene, not to scale4. Final sketch—completed later with lots of time and detail,

drawn to scale

4 techniques for measuring evidence

1. Triangulation (indoor)

2. Rectangular coordinates (indoor)

3. Baseline (outdoor)

4. Polar coordinates (outdoor)

RPRP

evidence

RP

evidence

evidence

evidence

evidence

RP

evidence

RP

CS Sketching Lab Tips Label North Label RP Use rectangular coordinates to

measure evidence Symbols

Evidence in final sketch: Draw in body only, for all

others use LETTERS Measure to center of object Do not include evidence

measurements in sketch, they will be in your evidence table

Use RULER in final sketch and tables

Final sketch drawn to SCALE (include key to scale)

Evidence table

Use detail when including item description (ie. Book . . . What book? Size?—measure dimensions)

Letter Item/description LocationFrom N From W

A

B

C

Body

window

door

CS Sketch Example

= 1foot