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Scenario:
After seeing a movie, you and a
group of friends walk to your car in
the parking lot to find the driver'sside
window shattered and the door wide
open. Looking inside the car, you find
that your stereo/iPod and all of your
belongings have been stolen.
Questions:
- What specific evidence could have been left in or around your
car to help the police find the person or persons who committed
this crime?
- What should you and your friends do to preserve any evidence
that may be present?
- If a friend or family member witnessed the crime, would he or
she be a more or less reliable witness? Why or why not?
- If an eyewitness to a crime is a relative, friend or acquaintance
of the person committing the crime, would he or she be a more or
less reliable witness? Why or why not?
CSI Assignment: Due Friday, Sept. 19th
Read Chapter 2 in your text. Watch an epsiode of CSI, NCIS, or other crime
drama in which they examine crime scenes and evidence. If you cannot
catch one on TV, episodes are available on hulu.com or various other web
sites. In a short paper, discuss/answer the following, including at least 2
quotes or references to your text with page numbers (APA or MLA):
Give the title and explain the general story line of the episode.
What are some examples of direct, indirect, physical, biological,
and/or trace evidence? Be sure to describe which is which.
How was the crime scene secured? What things did they do that
are discussed in your book as appropriate?
What mistakes, if any, were made in securing the crime scene?
What evidence could have been compromised and how?
Extra Credit
Bring in a maximum of 2 magazines (not just small ads
or catalogs). We will be using them so do not expect
them back.
5 points per magazine
Due no later than Monday Sept. 15th
Chapter 2 Crime Scene Investigation
and Evidence Collection
By the end of this chapter you will be able to:
- summarize^ Locardâs^ exchange^ principle
- identify^ four^ examples^ of^ trace^ evidence
- distinguish^ between^ direct^ and^ circumstantial^ evidence
- identify^ the^ type^ of^ professionals^ who^ are^ present^ at^ a^ crime
scene
- summarize^ the^ seven^ steps^ of^ a^ crime^ scene^ investigation
- explain^ the^ importance^ of^ securing^ the^ crime^ scene
- identify^ the^ methods^ by^ which^ a^ crime^ scene^ is^ documented
- demonstrate^ proper^ technique^ in^ collecting^ and^ packaging
trace evidence
- describe^ how^ evidence^ from^ a^ crime^ scene^ is^ analyzed
Crime Scene Investigation A
multidisciplinary approach in which scientific
and legal professionals work together to
solve a crime.
goal is to recognize, document,
and collect evidence at the scene of
a crime
Principle of Exchange
Dr. Edmond Locard, director of the worldâs first
forensic lab (1910, Lyon, France), established the idea of
the exchange principle; namely that:
- When a person comes in contact with an object or
another person, a crosstransfer of physical material can
occur.
- Study of the material can determine the nature and
duration of the transfer.
Trace evidence small but measurable amounts of
physical or biological material found at a crime
scene In addition, the intensity, duration, and nature of the
materials in contact determine the extent of the
transfer.
Types of Evidence
- Statements of a witness in court would be
direct evidence evidence that (if true) proves
an alleged fact.
- Indirect^ or^ circumstantial^ evidence,^ such^ as^ a
fingerprint (physical evidence) or blood or hairs
(biological evidence), would imply a fact but
does not prove it directly. This is trace
evidence
- Class^ evidence^ is^ connected^ to^ a^ certain
group.
- Individual evidence identifies a particular
person or thing.
Types of Evidence
Evidence taken from a crime scene.
Direct or circumstantial evidence?
Physical or biological evidence?
Class or individual evidence?
Explain why this would be or would not be
trace evidence.
Magazine Activity
1. Tape two or four sheets of colored paper together so
you have a large surface area on which to work.
2. Cut out pictures from the magazines and glue/tape
them to the colored paper.
pictures must represent evidence for solving a crime.
you choose at least four pictures for EACH of the
following types of evidence: direct, physical, biological
(you will have 12 pictures total)
3. On the back of the colored paper, you must explain
what each picture represents and the type of evidence it is.
BE SURE TO PUT YOUR NAME ON THE BACK OF THE
PAPER BEFORE YOU TURN IT IN.
The Crime Scene Investigation Team
Who is at the crime scene?
- Police^ usually^ the^ first^ to^ arrive^ (first^ responder)^ and
possibly a district attorney who can determine if a search
warrant is necessary.
- Crime scene investigators document the scene in
detail and collect evidence. May include recorders, sketch
artists, photographers
- Wet evidence put in paper container and allowed to
dry. If not, DNA will degenerate and evidence will
become moldy and useless.
*FBI and state agencies have standards for collecting
and storing all different types of evidence.
Control samples
obtained from victim for exclusionary purposes
if blood found at crime scene if victim's it is excluded
from further study
Packaging the evidence
- Crease^ a^ clean^ paper^ and^ place^ the^ evidence^ in
the X position (as shown above).
- Fold in the left and right sides
- Fold^ in^ the^ top^ and^ bottom.
- Insert^ the^ top^ flap^ into^ the^ bottom^ flap^ then^ tape
closed
- Put the bindle into a plastic or paper evidence bag
- affix^ a^ seal^ over^ the^ opening.
- Write^ your^ name^ on^ the^ seal.
- FBI and state agencies publish standards of
collection for different kinds of evidence
Chain of Custody
In order to present credible evidence in court, a chain of
custody log is essential.
- The^ person^ who^ finds^ the^ evidence,^ bags^ it,^ marks^ it^ for
identification, seals it, and signs it across the sealed edge (above,
left).
- It is signed over to a technician in a lab for analysis who opens it,
but not on the sealed edge.
- After analysis, the technician puts it back in the evidence bag,
seals it in another bag, and signs the evidence log (above, right).
You are crime scene investigators and have found a white shirt belonging to
one of the suspects at the scene of the crime. The shirt and/or the surrounding
area (this classroom) must be examined for trace evidence to link it to one of
the suspects.
All procedures for collecting evidence must be followed.
*Only pick up fibers and hairs from the evidence with forceps (tweezers).
The trace evidence from the shirt must be properly handled, put in paper
bindles, placed in evidence bags along with the completed evidence log, sealed
and labeled.
Once this is completed, you MUST have Mrs. Rynearson check your
evidence bag to ensure you have packaged it properly.
Then trade bags with one other person who has also had their evidence
checked. You are now the technician and must open and reseal the evidence
PROPERLY and fill in the appropriate spaces on the chain of custody at the
bottom of the evidence label.
Once this is complete, you MUST have Mrs. Rynearson check your
second bag to ensure you have done it properly.
Analyze the Evidence
- FBI^ crime^ lab^ is^ one^ of^ the^ largest^ forensic^ labs^ in^ the
world.
- The^ facts^ of^ the^ case^ are^ determined^ when^ the^ forensic
lab processes all the collected evidence.
- Unlike TV, lab technicians are specialized and process
one type of evidence.
- The^ lab^ then^ sends^ the^ results^ to^ the^ lead^ detective^ who
aims to see how it all fits into the crime scenario.
crimescene reconstruction: forming a hypothesis of
the sequence of events from before the crime was
committed through its commission.
evidence does not lie, but investigators must
interpret the evidence.
Analyze the Evidence
The lab results can:
⢠Show^ reliability^ of^ any^ witness
accounts.
⢠Establish^ the^ identity^ of^ suspects^ or
victims.
⢠Show suspects to be innocent or link
them with a scene or victim.
Crime Scene Reconstruction
⢠Evidence could be staged
⢠must^ examine^ all^ possibilities
Staged Crime Scenes
When the lab results do not match up with the
testimony of witnesses, it can mean the crime was
staged; common examples include:
- Staging^ a^ fireâto^ cover^ bankruptcy.
- Staging^ a^ suicideâto^ cover^ a^ murder.
- Staging^ a^ burglaryâto^ collect^ insurance^ money.
Staged Crime Scenes
To help determine whether a crime scene
was staged, consider:
- Whether the type of wound found on the victim matches
the weapon employed.
- Initially treat all death certificates as homicides.
- Profile of the victim through interviews of family/friends.
- Whether the wound could have been easily selfinflicted.
- The mood and actions of the victim before the event.
- The mood and actions of a suspect before the event.
- Whether statements corroborate with evidence
Summary
- Locardâs^ exchange^ principle:^ contact^ between
people and objects can transfer material that can
determine the nature and duration of the transfer.
- Evidence can be direct or indirect (physical or
biological).
- A^ crime^ scene^ investigation^ team^ consists^ of
police, detectives, crime scene investigators,
medical investigators, and specialists.
- The investigation consists of recognizing,
documenting, and collecting evidence.
Summary
- First^ responding^ officers^ identify^ the^ extent^ of^ the
crime scene, secure it, and segregate witnesses.
- Crime scene investigators document the crime
scene.
- Evidence must be collected, packaged, and
labeled.
- The evidence then is analyzed and interpreted to
fit the crime scenario.
