1. Forensic Science
Criminalistics
Chapter 2
The Crime Scene

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

3. Securing and Isolating a Crime Scene
Duties of the Arriving Officer:
Get medical attention for suspect or victim
Arrest perpetrator if remaining on premises
Secure the Crime Scene

4. Securing and Isolating a Crime Scene
The Arriving Officer must prevent unauthorized or unneeded access:
Unnecessary police officers
Neighbors/Onlookers
Members of the Media
Every individual entering a crime scene can potentially destroy important evidence

5. Evaluate the Crime Scene
The Lead Investigator will:
Determine the boundaries of the scene
Document and photograph obvious evidence
Develop a strategy for a systematic examination and documentation of entire scene

6. Methods of Crime Scene Recording
Photography & Videography
May be limited by budget/personnel
Detailed Sketches with accurate measurements
Detailed Notetaking with descriptions of evidence collected

7. Crime Scene Photography
The crime scene must be unaltered and in the original state found by investigators
Must be photographed from all necessary angles
Evidence must not be moved prior to photography: if it has been moved, it cannot be reintroduced into the scene for photo purposes

8. Crime Scene Photography
Photos must be taken of the entire room and all rooms adjacent to initial crime scene
Close-up photos and panoramic photos are taken and sometimes include a ruler for scale
All pieces of physical evidence are photographed prior to removal

9. Crime Scene Videography
Increasingly popular due to affordable cost
Long-shots and close-ups are taken of scene
Narrations are often included as a method of note-taking

10. Crime Scene Sketching Rough Sketch:
An accurate depiction of dimensions of the scene, showing the location of all objects that may have implications to the crime.
Done at the scene and used for finished sketch later

12. Rough Sketches
Objects are depicted from two fixed locations at the scene
Accurate measurements must be taken with a tape measure
Sketch evidence by using letters or numbers and a legend at the bottom
Sketch should always depict the NORTH direction

13. Finished Sketch A precise depiction of the crime scene, drawn to scale
Sometimes drawn with the aid of a computer
CAD: Computer-aided drafting

14. Notetaking at a Crime Scene
Constant activity at a crime scene that includes the following:
A written description of the scene in a narrative format
Location of physical evidence items recovered
Time evidence discovered and by whom
The condition of the evidence recovered

16. Typical types of Crime-Scene Searches
Spiral Search Method: Begins from one point of the crime scene and continues in a spiral fashion to another point

17. Typical types of Crime-Scene Searches
Strip or Line Search: Several investigators begin side-by-side and search in a straight line and turn around and continue back on an adjacent part of the area

18. Typical types of Crime-Scene Searches
Grid Search: Investigators begin a search in an S-pattern from the a border of a crime scene and overlap the S-pattern on return

19. Typical types of Crime-Scene Searches
Quadrant or Zone:
A small area or room is searched. It's used in homicides, rape, drug and bomb searches. 

20. Types of Physical Evidence to Look For:
1. Blood, semen, saliva, sweat 

21. 2. Hair/Fibers

22. 3. Documents

23. 4. Fingerprints

24. 5. Glass/Paint/Powder Residues

25. 6. Victim’s clothing

26. 7. Fingernail Scrapings

27. 8. Recovered bullets from the body

28. Integrity of Evidence
Blood, hairs/fibers, soil and dust should be submitted intact and should not be removed from garments or surfaces
When these items are found on large objects that cannot be removed easily, evidence can be removed carefully using forceps or swabs

29. Packaging Evidence
Use wrapping paper, manila envelopes, paper bags are used for blood stained material
Airtight containers are never used because they can readily grow molds and destroy evidence
Airdry wet/bloody clothing and place in paper bags

30. Packaging Evidence
Use airtight containers for charred evidence from fires
Prevents evaporation of accelerant
Common packaging:
Empty, unused paint cans
Tightly sealed jars

31. Chain of Custody
A list of all persons who came into possession of an item of evidence
May include: collector, carrier, lab tech, evidence storage officer, investigator, medical examiner, etc
Unnecessary personnel should not handle evidence without justification prevents contamination

32. This is an example of a chain of custody tag that should be attached to each piece of evidence to show who all has had possession of the evidence.

33. Standard/Reference Samples
Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared with crime scene evidence
Used as a comparison method to incriminate or exonerate a suspect or to identify a victim

34. Submitting Evidence to a Lab
May be completed by delivery or by mail
Should be done by someone familiar with the case
Includes an “Evidence Submission Form” stating the case history and type of exam requested
Must maintain Chain of Custody in all cases

35. Evidence Submission Form

36. Crime Scene Safety: Ways to Reduce Risks
Wear double gloves, protective footwear and clothing
Use masks/respirators, goggles or face shields
Be alert to sharp objects such as knives, needles, razor blades, etc.
Dispose of contaminated objects such as soiled gloves and clothing items that were worn by personnel

37. Crime Scene Safety: Ways to Reduce Risks
Complete notetaking with uncontaminated gloves to prevent contamination of pens and notebooks
Remove torn or contaminated material and discard immediately
No eating, drinking or smoking at the scene
All nondisposable linens or clothing should be labeled and laundered properly

38. Legal Considerations at the Crime Scene
All removal of evidence from a person or from the scene must conform to the Fourth Amendment:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

39. Warrantless Searches Existence of emergency situations
Prevent the immediate loss or destruction of evidence
Search of a person or property following a lawful arrest
Search by consent

40. Mincey v. Arizona
After a homicide, police searched a scene for four days. Evidence collected was found to be inadmissible in court because the court did not feel that evidence would have been lost or destroyed in the time needed to obtain a legal search warrant.

41. Michigan v. Tyler
Fire destroyed a building and evidence was collected the first day at the scene. After the initial entry, later entries into the building produced evidence. All evidence from later entries to the property were deemed inadmissible in court.