Crime-Scene Investigation and Evidence Collection

1. Crime-Scene Investigation and Evidence Collection

2. Objectives

4. Are there cars parked on the sides of the road? • What color is the pickup truck driving in the road? • Any minivans around? • What does the blue sign say? • What’s the speed limit? • Are there any pedestrians on the road?

5. Locard’s Exchange Principle • When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur • Hair, skin cells, clothing fibers, pollen, glass fragments, debris from clothing, makeup, soil • Called trace evidence • pet hair on clothes • Hair on your brush • Fingerprints on glass • Soil tracked into house • Drop of blood on t-shirt • Used tissue • Paint chips • Broken glass • Fiber from clothing

6. Evidence • Classified two different ways – • Direct evidence • Circumstantial evidence • Physical evidence • Biological evidence • Trace evidence

7. Direct Evidence • Firsthand observations such as eyewitness accounts or police dashboard video cameras • Confessions • Testimony by a witness in court

8. Circumstantial Evidence • Indirect evidence that can be used to imply a fact but that does not directly prove it • Link between crime scene and a suspect • Physical – Impressions, fingerprints, footprints, shoe prints, tire impressions, tool marks, fibers, weapons, bullets, shell casings • Reduces number of suspects to a specific, smaller group • Biological – body fluids, hair, plant parts, natural fibers • Makes the group of suspects very small, or reduces it to a likely individual

9. Class vs. Individual Evidence • Class – narrows identity to a group of persons or things • Ex – blood type • Individual – narrows an identity to a single person or thing • Ex – fingerprints

10. The CSI Team • Police officers • District attorney • Crime scene investigators • Medical examiners • Detectives • Specialists

11. The Crime Scene Investigation Team • Police officers – secure the scene • District attorney – determine whether search warrant is necessary • Crime-scene investigators – document crime scene in detail and collect physical evidence • Recorders, sketch artists, photographers, evidence collectors • Medical examiners – determine cause of death if homicide • Detectives – look for leads by interviewing witnesses and talking to crime-scene investigators about evidence • Specialists – consulted if the evidence requires their expertise • Entomologists, forensic scientists, forensic psychologists, etc.

12. The Seven S’s of Crime Scene Investigation • Securing the scene • Separating the witnesses • Scanning the scene • Seeing the scene • Sketching the scene • Searching for evidence • Securing and collecting evidence

13. 1. Securing the Scene • Responsibility of the first responder (usually a police officer) • Restricts all persons not authorized from entering • Security log of all entering and exiting • May request various experts to be sent to scene • First Priority – safety of all individuals • Second Priority – preservation of evidence

14. 2. Separating Witnesses • Witnesses must not be allowed to talk to one another! • Questions to ask: • When did the crime occur? • Who called in the crime? • Who is the victim? • Can the perpetrator be identified? • Where were you when you observed the crime scene?

15. 3. Scanning the Scene • Scan the scene to determine where photos should be taken • Primary crime scene – where crime took place • Secondary crime scene – location linking to crime • Ex: Primary scene - front of store where robbery took place Secondary scene – home of suspect Ex: Primary scene – location of murder Secondary scene – location where corpse was found

16. 4. Seeing the Scene • Crime examiner needs to see whole scene • NEEDS TO BE IN UNALTERED POSITION!!! • Photos of overall area • Close-up photos • Photos with and without a measuring ruler • View of crime scene from different angles and distances • Close-up photos of any evidence and bodies • Photos need to be taken before evidence or body is moved

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24. Evidence

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38. 5. Sketching the Scene • Rough sketch – notes position of body and any other evidence • All objects measured from two immovable landmarks • North should be labeled, scale included for distance • Doors, windows, furniture • If outdoors, position of trees, vehicles, hedges, other structures • Drawn AT the scene • Also include – name, date, location, conditions outside or inside

39. Figure 2–4  Rough-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com.

40. 5. Sketching the Scene • Final Sketch – include all the aspects of a rough sketch but more accurate • Possible for presentation in court • Computer programs available now • Drawn in the lab AFTER searching the crime scene • Note-taking also occurs throughout entire process

41. Figure 2–5  Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com

42. 6. Searching for evidence • Scene should be walked and location of evidence marked, photographed, and sketched • Patterns: • Spiral • Grid • Linear • Quadrant or Zone • Single investigator – grid, linear, or spiral pattern • Group of investigators – linear, zone, quadrant

44. 7. Securing and Collecting Evidence • All must be properly packaged, sealed, and labeled • Liquids and arson – stored in airtight, unbreakable container • Biological evidence – stored in breathable containers so air can dry out • Wet evidence – stored in paper and allowed to air dry • NEVER place wet evidence in an airtight container; will cause mold and degrade DNA • Paper bindle – paper used to store evidence • Placed into evidence bag and labeled

45. Standards • There are many standards for collecting different types of evidence • Example: National Institute of Justice

46. Control Samples • Obtained from the victim for the purpose of exclusion • Ex - blood samples found on a victim or at crime scene compared to victim’s blood • If they match, sample is victims and no further tests run • If not, may have come from suspect and further testing is completed!

47. Evidence Log • Case number • Item inventory number • Description of evidence • Name of suspect • Name of victim • Date and time of recovery • Signature of person recovering evidence • Signature of any witnesses present during collection

48. Chain of Custody • Each person who handles the evidence must be recorded properly • When evidence is found – marked with proper information and placed in a collection bag • Container is sealed and collector’s signature is written across sealed edge • Next person responsible opens at a location other than sealed edge, completes exam, reseals in new packaging and signs chain of custody log! • Pattern continues!

49. Chain of Custody • EXTREMELY important for courtroom! • All who handled evidence could be asked to appear in court • Process must show evidence was handled properly and every person handling it was recorded