1. The Crime Scene
Chapter 2

2. Physical Evidence
Any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator.
The recognition of physical evidence is essential to the success of the crime lab.
Types
Direct (testimonial)
first-hand observations, confessions, video
Circumstantial
Indirect evidence can imply a fact but not prove it
Suspects fingerprints at the scene

3. Class vs. Individual Class evidence Individual evidence
Narrows identity to a group of items of people
Individual evidence
Narrows identity to a single person or thing

4. Classification of Evidence
Circumstantial
Class
Individual
Direct

5. No amount of expensive, sophisticated lab equipment can salvage the investigation if physical evidence is not recognized and correctly collected and preserved.
In reality only crimes of a serious nature will require evidence collection

6. What is a crime scene?
Primary crime scene—site of the original criminal activity
Ex:site of homicide
Secondary crime scene—site of any subsequent crime. Can be multiple in number
Ex: Where the body was dumped
All crime scenes are unique and the boundaries of a crime scene are flexible.

7. ADAPT
A Assess the crime scene and assist those hurt (Saving lives is most important)
D Detain the witness (need these guys for questioning)
A Arrest the perpetrator (many times they will hang around to admire their handy work)
P Protect the crime scene (this is where the yellow tape comes in)
T Take notes (notes are very important especially when the case goes to court)

8. Securing the Crime Scene
Anyone who enters the crime scene can alter or change the scene and its evidence
Access should be limited to crime scene personal and a contamination log should be kept.
Witnesses are separated to prevent collusion.
Must be guarded 24hrs a day until released
A walk-through should be completed

9. Walkthrough Preliminary scene survey
Mentally reconstruct the crime (this can be changed or adapted)
Determine the boundaries
Note any temporary evidence that requires immediate processing or protection
Make a note of weather conditions and take precautions if necessary

10. Record the Scene To preserve the original state of the scene
The original state will only be available for a limited amount of time
Tools:
Photography
Sketches
Videography
Notes

11. Notes
Must include a detailed written description of the scene with the locations of where physical evidence was recovered
Must identify the time physical evidence was recovered, by whom, how, and by whom it was packaged and marked
Tape-recording and narrating a video tape can be faster than writing.
At some points notes must be transcribed

12. Videography
Done without verbal commentary except for factual info such as date and time
Should include both general and specific areas
View of the crime scene from the victim’s point of view

13. Photography Done immediately after videotaping
Better to take too many than to few
If an object has been moved it can not be returned to be photographed

14. Diagram
Make a diagram or sketch that shows the spatial relationships that a photograph cannot

15. Search for Evidence Depends on the location of the crime
Evidence searched for depends on the nature of the crime
Important to note what is missing as well

16. Uses for Physical Evidence
Info on modus operandi
Info on corpus delicti
Info used to determine the essential facts of an investigation
Linking persons, scenes, and objects
Verifying witness statements
ID suspects
AFIS
CODIS
ID unknown Substances
Crime Reconstruction

17. Theories behind searches
The Linkage Theory
The theory that if investigators can establish positive links between evidence, the crime scene, and the suspect then the case may be solved
Ex: Bloody fingerprints on the victim’s wrist and on the door knob would be useful while bloody fingerprints on only the doorknob would be less useful.

18. Theories behind searches
Locard’s Theory of Exchange
Transfer evidence is created whenever two objects come into contact with each other.
Primary transfer---victim bleeding onto floor
Secondary transfer---suspect steps in blood on the floor and tracks it through the crime scene

19. Search Patterns

20. Search Methods
Line
Lots of people walk side by side across some large area like a field.
Very easy and works well in outdoor areas
Can be modified into the strip method by dividing the area into a rectangle which is then divided into strips

21. Search Methods
Grid
After the line method has been used the area is searched perpendicular to the original area so that if the searches were over laid they would form a grid
Benefit is that two different people search the same area

22. Search Methods Wheel Spiral method
Viewed as a wagon wheel with spokes. Begin at the center and move outward
Not useful in large areas because the gaps between searchers become too great.
Spiral method
Scene is viewed as a circle. Begin in the center and spiral out or vice versa

23. Search Methods Zone method Link Method
Crime scene is divided into zones. Each zone is searched by an investigator then when finished another investigator searches the zone. Works well indoors
Link Method
Does not follow a geometric pattern. Works with the linkage theory. Once an item is found investigators then search for the next logical item. Such as if they find a tool mark then they search for the tool that made it.

24. Evidence from the victim
The following should be collected:
Victim’s clothing
Fingernail scrapings
Hair samples
Blood
Hand swabs (gunshot residue)
Bullets from the body
Vaginal and oral swabs (if appropriate)

25. Collect and Package Evidence
Must be handled and packaged in a way that prevents any change from taking place between when it is removed from the crime scene and delivered to the crime lab.

26. Evidence
Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

27. Packaging Evidence 1. Choose the right size paper for a bindle.
2. Place evidence into paper bindle and tape closed.
3. Place bindle inside a paper/plastic evidence bag. Fold bag closed.
4. Place seal over folded edge.
5. Collector should write his or her name over the folder edge.

28. Let’s Make a Bindle

30. Bloodstained materials
Packaging of manila envelopes, paper bags or wrapping papers are used to prevent mold contamination
Allow to air dry first

31. Charred Debris
Sealed in an air tight container to prevent the evaporation of petroleum residues

32. Chain of Custody
A list of all persons who came into possession of an item of evidence
Should be kept to a minimum

33. Standard/Reference Samples
Physical Evidence whose origin is known that can be compared with crime scene evidence
Substrate controls
Uncontaminated surface material close to an area where physical evidence has been deposited (particularly used in arson investigation and bloodstain analysis)

34. Legal Considerations Fourth Amendment Right Warrant-less search
Emergency circumstances
Prevent immediate loss or destruction of property
Incident of lawful arrest
Consent of parties involved
However, when time and circumstances permit a search warrant must be obtained

35. Mincey V. Arizona
Four day search conducted without a warrant after the death of an undercover officer during a narcotics raid of Mincey’s apartment.
Mincey released on appeal due to warrantless search
“No exigent circumstances to justify a warrantless search”.

36. Michigan v Tyler Business destroyed by fire suspected to be arson
Warrantless searches conducted 4, 7, and 25 days after the fire
Conviction was overturned.
Entry due to fire required no warrant but subsequent searches had to follow warrant procedures.