Forensic Science

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. The Value of Physical Evidence Physical Evidence is only valuable when collection is performed with selectivity that is determined by the collector’s knowledge of the capabilities of the crime lab

4. Forensic Science begins at the Crime Scene Physical evidence must be recognized and properly preserved for lab examination or it is useless to investigators and/or prosecutors in a court of law

5. 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

6. 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

7. Once the crime scene has been secured, a Lead Investigator begins the process of evaluating the immediate area as well as adjacent areas to the crime scene.

8. 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

9. Record the Crime Scene • Accurate records are important for investigators and prosecutors • Useful in subsequent investigations • Document the exact condition of crime scene • Mark exact location of physical evidence

10. 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

11. 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

12. 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

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

14. 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

15. 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

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

17. 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

18. Notetaking at a Crime Scene • Tape Recording may also be used to record a crime scene • Videotaping a scene with narration may also be used • All tape/video recordings must be transcribed onto paper for recordkeeping

19. Search for Evidence • Must be thorough and systematic • How the search is carried out depends on the location and size of the area and the actions of the suspect(s) and victim(s)

20. 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

21. 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

22. 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

23. Typical types of Crime-Scene Searches • Quadrant or Zone Search: Investigators divide crime scene into four sections then search one section at a time until the entire area has been searched

24. Typical types of Crime-Scene Searches What type of search conducted depends on: • Size of the crime scene • Complexity of the crime scene • Manpower available to conduct the search

25. Physical Evidence at a Crime Scene • Can be macroscopic to microscopic • Trace evidence may be found on clothing, in automobiles, etc. • All items must be handled and packaged with care to preserve the evidence

26. Physical Evidence at Autopsy • Items routinely sent to the crime lab: • Victim’s clothing • Fingernail scrapings • Head and pubic hairs • Blood (for DNA typing) • Vaginal, anal, and oral swabs for sex crimes • Recovered bullets from body • Hand swabs from shooting victims for gunshot residue

27. Collecting and Packaging Evidence Physical evidence must be collected and packaged carefully to prevent contamination, breakage, evaporation, and accidental scratching and/or bending.

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. Integrity of Evidence • Each different item or similar items collected at different locations must be placed in separate containers • Prevents damage • Prevents cross-contamination of specimens

30. Packaging Evidence • Use forceps for picking up small items • Use unbreakable plastic bottles with pressure lids for hair, glass, fibers, and other small trace evidence • Manila envelopes and screw-cap glass containers may also be used for trace evidence • “Druggist-fold” Envelopes may also be used

31. 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

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

33. 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

34. 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

35. 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

36. Crime Scene Safety • Increased risk of AIDS and Hepatitis B infection to responding officers at a crime scene • Precautions must be taken for officers to protect themselves from all types of hazards

37. 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

38. 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

39. 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.

40. 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

41. 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.

42. 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.