1. CSI and Evidence

2. Principle of Exchange
Dr. Edmond Locard, director of the world’s 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 cross-transfer of physical material can occur.
Study of the material can determine the nature and duration of the transfer.
Forensic Science: Fundamentals & Investigations, Chapter 2

3. The Crime Scene Investigation Team
Who is at the crime scene?
Police and possibly a district attorney.
Crime scene investigators.
Medical examiners.
Detectives.
Specialists.
Forensic Science: Fundamentals & Investigations, Chapter 2

4. The Seven S’s of Crime Scene Investigation
Secure the scene
Separate the witnesses.
Scan the scene.
See to it that the crime scene examiners receive overall and close up photos with and without measuring rulers.
Sketch the scene.
Search for evidence.
Secure the collected evidence.
Forensic Science: Fundamentals & Investigations, Chapter 2

5. Securing Preserve and protect the area
Exclusion of unauthorized personnel
Isolate the area
Separate the witnesses.
Scan the scene.
See to it that the crime scene examiners receive overall and close up photos with and without measuring rulers.
Forensic Science: Fundamentals & Investigations, Chapter 2

6. Recording the Scene
Very important to document the condition of the scene and to delineate the location of physical evidence.
Photography, sketches, and notes are the 3 methods for crime-scene recording
Must be very detailed throughout the process
Forensic Science: Fundamentals & Investigations, Chapter 2

7. Photography
All objects must be photographed from all angles before moving anything
If items are moved, positions changed, or items added, the photographs may NOT be admissible in court
When the size of an item is significant , a ruler may be inserted near the object and included in the photo as a frame of reference.
Every photo, positioning, angles, and movement of the photographer should be recorded in the notes along with detailed pictures and descriptions of the scene, adjacent, areas, entrances and exits, and any other evidence
Forensic Science: Fundamentals & Investigations, Chapter 2

8. Sketching the Scene Rough Sketch
A Rough sketch must contain an accurate depiction of the dimensions of the scene and show the locations of all objects.
Objects are located in the sketch by distance measurements from 2 fixed points, such as the walls of a room.
All measurements must be accurate with no estimations
A legend is placed below the sketch that correlates the item letter or number to the description.
There should be a compass heading designating North
Finished Sketch
Must reflect information from the rough sketch in order to be admissible evidence in court.
Forensic Science: Fundamentals & Investigations, Chapter 2

9. Forensic Science: Fundamentals & Investigations, Chapter 2

10. Forensic Science: Fundamentals & Investigations, Chapter 2

11. Types of Evidence
Statements of a witness in court would be direct evidence.
Indirect or circumstantial evidence, such as a fingerprint (physical evidence) or blood or hairs (biological evidence), would imply something, and is called trace evidence.
Forensic Science: Fundamentals & Investigations, Chapter 2

12. Examples of Trace Evidence
Pet hair on clothes or rugs
Fingerprints on a glass
Soiled tracks in the house
Blood on a shirt
Used Tissue
Paint chips
Forensic Science: Fundamentals & Investigations, Chapter 2

13. 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.
Forensic Science: Fundamentals & Investigations, Chapter 2

14. Search for Evidence
Investigator in charge assigns personnel to search a scene
If possible, one person should supervise and coordinate the collection of evidence
May subdivide the scene into segments and search individually or the search may start at the outward points and gradual move toward the center in a circular fashion
The methods used should be documented along with steps within the scene
Forensic Science: Fundamentals & Investigations, Chapter 2

15. Forensic Science: Fundamentals & Investigations, Chapter 2

16. Evidence Collection
Integrity of evidence MUST be maintained when an item is collected
All clothing MUST be placed in air-dried containers and placed in separate bags to ensure constant circulation of air
Bloodstained materials should be in airtight containers to prevent the accumulation of moisture produces mold and mildew
**If additional evidence needs to be collected after the initial timeframe, a search warrant must be presented.
Forensic Science: Fundamentals & Investigations, Chapter 2

17. Packaging the evidence – “druggist fold”
Crease a clean paper and place the evidence in the X position (as shown above).
Fold in the left and right sides, and then fold in the top and bottom.
Put the bindle into a plastic or paper evidence bag affixing a seal over the opening.
Write your name on the seal.
Used for small amounts of trace evidence
Forensic Science: Fundamentals & Investigations, Chapter 2

18. Chain of Custody
In order to present credible evidence in court, a chain of custody log is essential.
A person bags the evidence, marks it for identification, seals it, and signs it across the sealed edge (above, left). They must also include the location and date collected.
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).
Every individual who possesses the evidence must maintain a written record of its acquisition and deposition.
Forensic Science: Fundamentals & Investigations, Chapter 2

19. Analyze the Evidence
The facts of the case are determined when the forensic lab processes all the collected evidence.
The lab then sends the results to the lead detective who aims to see how it all fits into the crime scenario.
Forensic Science: Fundamentals & Investigations, Chapter 2

20. Analyze the Evidence The lab results can:
Show how reliable are any witness accounts.
Establish the identity of suspects or victims.
Show suspects to be innocent or link them with a scene or victim.
Forensic Science: Fundamentals & Investigations, Chapter 2

21. Crime Scene Reconstruction
Crime scene reconstruction involves:
forming a hypothesis
of the sequence of events
from before the crime was committed
through its commission.
Forensic Science: Fundamentals & Investigations, Chapter 2

22. 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 fire—to cover bankruptcy.
Staging a suicide—to cover a murder.
Staging a burglary—to collect insurance money.
Forensic Science: Fundamentals & Investigations, Chapter 2

23. 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.
Whether the wound could have been easily self-inflicted.
The mood and actions of the victim before the event.
The mood and actions of a suspect before the event.
Forensic Science: Fundamentals & Investigations, Chapter 2