1. Chapter 2 Crime Scene Investigation and Evidence Collection
SFS1. Students will recognize and classify various types of evidence in relation to the definition and scope of Forensic Science
Compare and contrast the history of scientific forensic techniques used in collecting and submitting evidence for admissibility in court (e.g. Locard’s Exchange Principle, Frye standard, Daubert ruling).
Distinguish and categorize physical and trace evidence (e.g. ballistics, drugs, fibers, fingerprints, glass, hair, metal, lip prints, soil, and toxins).
Determine the proper techniques to search, isolate and record evidence.
Recognize possible evidence at the site of an investigation, evaluate the relevance of the evidence to the investigation, and illustrate the proper techniques for the collection of physical and trace evidence.
Organize relevant information to accurately develop and submit both scene and analysis reports.
Forensic Science: Fundamentals & Investigations, Chapter 2
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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. Transfer
When you pet a dog and get dog hair on your shirt, that is primary transfer.
When you then go and hug someone and some dog hair goes from you to your friend’s shirt, that is secondary transfer.
If your friend then hugged someone and transferred the dog hair, what would that be?
Forensic Science: Fundamentals & Investigations, Chapter 2

4. 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

5. Individual vs Class Evidence
Individual Evidence: material that can be related to a single source; individualization always involves comparison
Class Evidence: material that can be associated only with a group of items that share properties or characteristics
Forensic Science: Fundamentals & Investigations, Chapter 4

6. Class vs Individual Evidence
These fibers are class evidence; there is no way to determine if they came from this garment.
The large piece of glass fits exactly to the bottle; it is individual evidence.
Forensic Science: Fundamentals & Investigations, Chapter 4

7. Types of Evidence
Forensic Science: Fundamentals & Investigations, Chapter 2

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

9. The Crime Scene
The first officer to arrive at the scene is responsible for securing the crime scene.
First priority should be given to obtaining medical assistance for individuals in need of it and to arresting the perpetrator.
Detain and separate witnesses
As soon as it is possible, remove all unauthorized personnel from the scene.

10. The Preliminary Exam
A lead investigator will start the process of evaluating the area.
Determine the boundaries of the scene
Establish the perpetrator’s path of entry and exit.
Do an initial walk-through of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.
Forensic Science: Fundamentals & Investigations, Chapter 2

11. Figure 2–7 Several typical examples of crime-scene search patterns
Figure 2–7  Several typical examples of crime-scene search patterns. The pattern selected normally depends on the size and locale of the scene and the number of collectors participating in the search.
Forensic Science: Fundamentals & Investigations, Chapter 2

13. Forensic Science: Fundamentals & Investigations, Chapter 2

14. Crime Scene Documentation
Videotaping the Crime Scene
Introduce with case #, date, location
Begin with surroundings (include entrance/exits)
Tape Evidence (wide angle, close-up)
Victims viewpoint
DO NOT:
Narrate the video or discuss contents
Edit original video

15. Photography
The most important prerequisite for photographing a crime scene is for it to be in an unaltered condition.
Unless there are injured parties involved, objects must not be moved until they have been photographed from all necessary angles.
Forensic Science: Fundamentals & Investigations, Chapter 2

16. (Columbine High School)

17. Sketches
Rough Sketch - A draft representation of all essential information and measurements at a crime scene. This sketch is drawn at the crime scene.
Finished Sketch - A precise rendering of the crime scene, drawn to scale. It can be done by hand or on a computer.
Forensic Science: Fundamentals & Investigations, Chapter 2

18. Figure 2–4 Rough-sketch diagram of a crime scene
Figure 2–4  Rough-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C.,
Forensic Science: Fundamentals & Investigations, Chapter 2

19. Figure 2–5 Finished-sketch diagram of a crime scene
Figure 2–5  Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C.,
Forensic Science: Fundamentals & Investigations, Chapter 2

20. Packaging
Each different item or similar items collected at different locations must be placed in separate containers.
Forensic Science: Fundamentals & Investigations, Chapter 2

21. Packaging There are many types of packaging materials you can use.
Forensic Science: Fundamentals & Investigations, Chapter 2

22. Packaging
Biological evidence placed in non-airtight container and allowed to dry
Liquid or volatile evidence placed in airtight containers
Forensic Science: Fundamentals & Investigations, Chapter 2

23. Packaging the evidence
Creating a bindle
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.
Forensic Science: Fundamentals & Investigations, Chapter 2

24. Chain of Custody
Chain of Custody—A list of all persons who came into possession of an item of evidence.
Adherence to standard procedures in recording the location of evidence, marking it for identification, and properly completing evidence submission forms for laboratory analysis is critical to chain of custody.
Forensic Science: Fundamentals & Investigations, Chapter 2

25. Chain of Custody
A person bags the evidence, 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).
Forensic Science: Fundamentals & Investigations, Chapter 2

26. 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

27. 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

28. Figure 1–10  An envelope containing anthrax spores along with an anonymous letter was sent to the office of Senator Tom Daschle shortly after the terrorist attacks of September 11, A variety of forensic skills were used to examine the envelope and letter. Also, bar codes placed on the front and back of the envelope by mail-sorting machines contain address information and information about where the envelope was first processed. Courtesy Getty Images, Inc.—Liaison
Forensic Science: Fundamentals & Investigations, Chapter 2

29. 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

30. A laser beam is used to determine the search area for the position of a shooter who has fired a bullet through a window and wounded a victim. The bullet path is determined by lining up the victim’s bullet wound with the bullet hole present in the glass pane.
Forensic Science: Fundamentals & Investigations, Chapter 2

31. 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

32. 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

33. The Crime Lab
At present, around 400 public crime laboratories operate at various levels of government—federal, state, county, and municipal.
Forensic Science: Fundamentals & Investigations, Chapter 2

34. The Crime Lab
The ever increasing number of crime laboratories is partly the result of the following:
Supreme Court decisions in the 1960s responsible for police placing greater emphasis on scientifically evaluated evidence.
Crime laboratories inundated with drug specimens due to accelerated drug abuse.
The advent of DNA profiling.
Forensic Science: Fundamentals & Investigations, Chapter 2