1. Crime-Scene Investigation and Evidence Collection
Chapter 2

2. Objectives Summarize Locard’s 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.

3. Crime Scene Investigation
Goal: recognize, document, and collect evidence at the scene of a crime
Piece together evidence to form a picture of what happened at the crime scene
Ability to reconstruct the scene

4. Trace Evidence
Small but measureable amounts of physical or biological material found at a crime scene
Examples: pet hair on clothes or rugs, hair on your brush, fingerprints on a glass, soil tracked into a house on your shoes, drop of blood on a t-shirt, broken glass, etc.
Physical transfer of trace evidence occurs when two people come in contact
Dr. Edmond Locard (world’s first forensic lab in Lyon, France) was first to note this condition

5. Trace Evidence

6. Locard’s Exchange Principle
1. When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur
Exchanged materials indicate that the two objects were in contact
Trace evidence can be found on both persons (and/or objects) because of cross-transfer
2. Intensity, duration, and nature of the materials in contact determine the extent of the transfer
i.e. fistfight vs. brushing past another person

7. Types of Evidence Direct Evidence Circumstantial Evidence
Includes firsthand observations
Ex: eyewitness accounts/testimony, police dashboard video cameras, confessions
Circumstantial Evidence
Implies a fact but does not directly prove it
Links crime scene to a suspect
Trace evidence
Physical or biological
Ex: finding a suspect’s gun at the site of a shooting

8. Circumstantial Evidence
Physical Evidence
Impressions – fingerprints, footprints, shoe prints, tire impressions, tool marks
Fibers, weapons, bullets, shell casings
Typically reduces the number of suspects to a specific, smaller group of individuals (exception?)
Biological Evidence
Body fluids, hair, plant parts, natural fibers
May make the group of suspects very small or reduce it to a likely individual
More persuasive in court

9. Types of Evidence Class Evidence Individual Evidence
Narrows an identify to a group of persons or things and excludes others
Ex: ABO blood type
Individual Evidence
Narrows an identity to a single person or thing
Ex: unique combination of characteristics, such as a fingerprint

10. CSI Team Police officers Crime-scene investigators
Typically first to arrive
Crime-scene investigators
Document scene, collect physical evidence
Recorders, sketch artists, photographers, evidence collectors
Medical examiners (coroners)
Determine cause of death
Detectives
Interview witnesses, talk to crime-scene investigators about evidence
Specialists
Consulted if evidence requires their expertise

11. Seven S’s of CSI Securing the scene Separating the witnesses
Scanning the scene
Seeing the scene
Sketching the scene
Searching for evidence
Securing and collecting evidence

12. Securing the Scene Police officer = First responder
First priority: safety
Determine need for medical assistance.
Second priority: preservation of evidence
Restrict unauthorized entry – security log of all who visit
Locard’s exchange principle
Protect from the elements!

13. Separating the Witnesses
Avoid collusion (working together to create a story)
Altering eyewitness testimony
Questions to be asked:
When did the crime occur?
Who called in the crime?
Who is the victim?
Can the perpetrator be identified?
What did you see happen?
Where were you when you observed the crime scene?

14. Scanning the Scene Where should photos be taken?
Primary crime scene – where the crime took place
Secondary crime scene – location other than primary scene where evidence is found

15. Seeing the Scene Photography! Overall view photographs
Items-of-evidence photographs
Close-up views with and without a measuring ruler
Triangulation of stationary objects included as reference points
Several different angles and distances

17. Sketching the Scene Rough sketch Final sketch
Notes position of body and other evidence
Objects measured using two immovable landmarks
Direction should be labeled and scale of distance provided
Other objects in vicinity of crime scene should be included
Final sketch
Typically to scale
Neater! Easier to read
Often on computer
Used in court proceedings

18. Sketching the Scene

19. Searching for Evidence
Systematic pattern for searching so no area goes unsearched
Single Investigator: search in grid pattern, linear pattern, or spiral pattern
Group of Investigators: linear pattern, zone pattern, quadrant pattern
Materials needed: additional light sources/flashlight for examination for trace evidence, forceps for collecting evidence
Oblique lighting!
Practice

20. Searching for Evidence

21. Securing and Collecting Evidence
Specific procedures and techniques based on type of evidence
Ex: liquids and arson in airtight, unbreakable containers, biological evidence in breathable containers to aid in drying and reducing mold
FBI and state police agencies publish descriptions of proper procedures for storing and collecting evidence
Paper bindle: holds biological evidence that has been air dried
Also called a “druggist’s fold”
Placed in plastic or paper container which is sealed with tape and labeled with signature of collector across the tape
Evidence log and chain of custody document attached to container

22. Packaging Evidence
Size of bindle depends on size of evidence (sheet of paper vs. large sheet of wrapping paper, etc.)
Large wet objects should be placed in paper container and sealed to allow to air dry and never packaged in plastic while wet!
DNA can degenerate and evidence can become moldy
Control samples must be obtained from the victim for the purpose of exclusion

23. Packaging Evidence Steps to packaging evidence
Choose appropriate-size sheet of clean paper
Crease the paper into nine sections
Place evidence in center
Fold left and right sides in
Fold in top and bottom
Insert top flap into bottom flap and tape closed
Place bindle inside plastic or paper evidence bag and fold bag closed.
Place a seal over folded edge of evidence bag
Collector writes his or her name over the folded edge

24. Evidence Log Case number Item inventory number Description of evidence
Name of suspect
Name of victim
Date and time of recovery
Signature of person recovering evidence
Signature of any witnesses present during collection

25. Chain of Custody
Final container for evidence is sealed and the collector’s signature is written across the sealed edge
Anyone who comes in contact from that point forward must sign the chain of custody form
When opened in the lab, it is opened at a location other than the sealed edge
Repackage in original packaging, resealed in new packaging with signature, and signs chain of custody

26. Chain of Custody Practice!
Bag the evidence Add identification Seal it Sign it across the sealed edge
Sign over to a lab technician Open bag on non-sealed edge
Return items to the evidence bag Seal evidence bag in another bag Sign the evidence log

27. Analysis of Evidence
Forensic lab technicians are specialized and process one type of evidence at a crime lab
Evansville Crime Lab
Lead detective receives laboratory results
End goal: crime-scene reconstruction
Lab results can:
Show reliability of witness accounts
Establish the identity of suspects or victims
Show suspects to be innocent (exclude them) or link them with a scene or victim

28. Crime Scene Reconstruction
Forming a hypothesis of the sequence of events from before the crime was committed through its commission
Compare evidence with witnesses’ statements and figure out how it all fits together
Maintain an open mind…why?

29. Staged Crime Scenes
Perpetrator makes the scene look like something it’s not
Lab results don’t match up with testimony of witnesses
Common examples:
Arson – staging a fire to cover up another crime
Suicide/murder
Burglary – staging to collect insurance money

30. Staged Crime Scenes
Initially treat all death investigations as homicides
Was the crime scene staged?
Consider…
Does the type of wound match the weapon?
Could the wound be easily self-inflicted?
What were the mood and actions of the victim before the event?
What were the mood and actions of the suspect before the event?
Corroborate statements with evidential facts
Reconstruct the event
Conduct all forensic examinations to determine the facts of the case

31. Case #1 – JonBenet Ramsey
Found dead in the basement of her home 12/26/96. Mother called 911 to say she was missing and that a ransom note was found.
Mistakes: didn’t search the house for 7 hours post- 911 call, only blocked off JonBenet’s bedroom, father found her in basement and covered her with a blanket and moved her to the living room, didn’t separate witnesses (parents) and get full statements, did not secure the house, pathology didn’t examine body for 18 hours after crime
Still unsolved! Maybe we will find out more on Dr. Phil on September 12?! Or CBS on September 18?

32. Case #2 – OJ Simpson
People vs. OJ
7:24-9:35
15:23-17:53
Simpson’s defense poked major holes in the LAPD’s forensic investigation processes that has led to changes in protocol. This is argued as the reason to which OJ Simpson was acquitted.
Documentation.  In 1994, the crime lab did not routinely document its handling of the evidence.  
Chain of Custody.  During the Simpson trial, there was a great deal of evidence that prosecution sought to produce at trial.  However, the source of that evidence was recorded and could not be explained.

33. Case #2 – OJ Simpson
Careful Examination of Evidence.  During the OJ murder investigation, no one noticed any blood on a pair of socks that were collected from Simpson’s bedroom until two months later when the socks were examined in the crime lab.  Defense experts suggested at trial that the blood was smeared on the socks while they were lying flat, not while someone was wearing them.
Proper Evidence Handling.  Forensic technicians were criticized for improperly packaging evidence samples and leaving them in a hot van on a summer day.  A rookie technician had collected most of the evidence in the murder case.  
Contamination of Evidence.  In 1994, a police detective took a blood sample from Simpson, and then carried the vial of Simpson’s blood in his pocket, back to the crime scenes.  At trial, the defense suggested that the blood was brought back to the crime scene for the purposes of planting that evidence at the scene.