Chapter 2: Crime Scene Investigation & Evidence Collection Flashcards
What is the goal of a crime scene investigation?
- to recognize
- to document
- collect evidence
When 2 people come into contact w/ each other a physical transfer occurs. These transferred materials are called _______.
Trace Evidence
- can be found on both ppl (or objects) bc of the cross transfer
Ex. hair, pet hair, paint, chemicals, soil/pollen, finger prints, etc.
Who is Dr. Edmond Locard?
- responsible for trace evidence
- direction of the 1st forensic lab in France
- Locard’s Exchange Principle
What happens during a cross transfer?
- a cross transfer of physical evidence occurs
- the intensity, duration, and nature of the materials in contact determine the extent of the transfer
What are the 2 Types of Evidence?
Direct Evidence
Circumstantial Evidence
Direct Evidence
1st hand observations
- eyewitness accounts
- police dashboard cameras
- confessions
Circumstantial Evidence
Indirect used to imply a tact but doesn’t prove
- provides 2 link between a crime scene and suspect
- trace evidence is an example
- 2 types
What are the 2 Types of Circumstantial Evidence?
Physical and Biological
Physical Circumstantial Evidence
- all types of evidence exempt for fingerprints reduces the # of suspects to a small specific group of ppl
Ex. fingerprints, footprints, shoe prints, tool marks, bullet shell casings
Biological Circumstantial Evidence
Any body fluids
Ex. blood, saliva, vomit, etc
Class Evidence
narrows an identity to a group of persons or things
Ex. ABO blood type found at a crime excludes all other blood types
Individualized Evidence
narrows down to a single person or thing
Who is involved in a crime scene investigation?
Police officers
District Attorney
Crime Scene Investigator
Medical Examiner
Detectives
Specialists
Police Officers
1st to arrive
District Attorney
may be present if a search warrant is necessary
Crime Scene Investigator
- sketch
- record evidence
- collect evidence
- take pictures
Medical Examiner
coroner determines the cause of death
Detectives
interviews witnesses & talks to investigators about the evidence
Specialists
- expertise
Ex. entomologists & forensic psychologists
Steps to Processing a Crime
- Secure the Scene
- Separate the Witnesses
- Scanning the Scene
- Seeing the Scene
- Sketching the Crime Scene
- Searching for Evidence
- Securing & Collecting Evidence
- Secure the Scene
- done by the 1st responding officer
- safety
- preservation of evidence
- prevent authorized ppl from entering the scene
- keep a log of who enters the scene
- may call for more help
- Separate the Witnesses
- witnesses should not talk to each other
- avoids a false story
- when did the crime scene occur?
- where were you?
- who called 911?
- Scanning the Scene
- to determine where the photo should be taken
- establish if there is a primary and secondary crime scene
Primary Crime Scene
location of the crime
Ex. Nicole Simpson murder place
Secondary Crime Scene
location related to the crime where evidence is found
Ex. OJ’s gloves outside of other house
- Seeing the Scene
- overall pictures
- close up pictures
- w/ or w/o rulers
- Sketching the Crime Scene
*- include case #, date, location, and investigator’s name
- accurate rough sketch should be made
- note the position of the body & evidence
- north should be labeled
- scale included
- if outside include the position of trees, cars, hedges & other structures
- more accurate copy is made for court at a later date
- Searching for Evidence
(search patterns)
4 Search Patterns
- 1. Grid
- 2. Linear
- 3. Quadrant or Zone
- 4. Spiral
- Securing & Collecting the Evidence
- all evidence needs to be packaged, sealed & labeled
- liquids & arson remains should be stored in airtight unbreakable containers
- moist biological evidence should be stored in breathable containers so it can dry out
- wet evidence should never be packaged wet
- evidence should be entered into log
How do you package dry evidence?
(lab)
- crease a clean paper & place the evidence in the x position
- fold in the left & right sides, and then fold in the top & bottom - called a bindle
- put the bindle into a plastic or paper evidence bag placing a seal over the opening
- write your name on the seal
What info needs to go into the evidence log?
(lab)
- Case #
- Item Inventory #
- Description
- Name of suspect
- Name of victim
- Date & time recovery
- Signature of the person who recovered the evidence
- Signature of any witness present during the collection
Analyzing the Evidence
(Who does it?)
- Done by a lab
- FBI crime lab
- Lab techs have specialists
- Lab results sent to detectives
- Results lead to crime scene reconstruction
Chain of Custody
- important to present credible evidence in court
- a person bags the evidence, marks it for identification, & signs across the sealed edge
- signed over to a lab tech, who opens it, but not at the sealed edge
- after analysis, lab tech puts the evidence back in the bags, seals it in another bags, and signs the evidence bag
Crime Scene Reconstruction
- forms a hypothesis about the sequence of events
- how does the evidence fit?
- evidence is compared w/ witness statements?
- provides connections
- establishes identities
- confirms testimony
- can be used to find s/o guilty or innocent
Ex. JonBenet house reconstruction, staircase
How to Determine if a Crime Scene is Staged
- evidence doesn’t match witness testimony
- arson
- suicide/murder
- bugerly
- treat all as death investigators
- do the wounds match teh type of weapon
> easily be self-inflicted? - establish a profile of the victim
- evaluate the behavior of the victim/suspect
- corroborate statements w/ evidence
- reconstruct the event
- conduct all forensic examinations to determine the facts of the case
