1. Crime Scene Investigation and Evidence Collection Lecture Goal to recognize, document and collect evidence at a crime scene

2. Locard’s Principle  Principle of Exchange –Part 1: Trace evidence is transferred upon contact –Person to person –Person to object –Part 2: Extent of transfer depends on –Intensity, duration, nature of materials Example: –Evidence under a fingernail

3. Types of Evidence Direct Circumstantial: indirect evidence firsthand observations: -eyewitness accounts -dashboard video cameras -confessions - used to imply but not prove a fact - may link a suspect and a crime scene ex. Suspect’s gun found at crime scene Physical: Impressions (fingerprints, footprints), fibers, weapons, bullets, shell casings reduces number of suspects to group Biological : may make group of suspects very small or even one individual Body fluids, hair, plant parts, natural fibers

4. Trace evidence: Hair (human or animal) Body fluids Fingerprints Soil tracked inside on shoes Drop of blood on shirt Used facial tissue Paint chips Broken glass Fiber from clothing

5. Forensic Science: Fundamentals & Investigations, Chapter 2 5 Types of Evidence Explain why this would be or would not be trace evidence

6. Individual evidence: single person, DNA, fingerprint, combination of unique traits Class evidence: narrows the identity to a group ex. Blood type ABO

7. Crime Scene Investigation Team: Police Officers: usually first (possibly a DA for a search warrant) Crime Scene Investigators: document crime and collect physical evidence –Recorder –Sketch artist –Photographers –Evidence collectors Medical Examiners: coroners may be necessary to determine cause of death Detectives: look for leads, interview witnesses and talking to the CSI about evidence Specialists: entomologists, psychologists

8. 7 S’s of CSI 1.Securing the Scene 2.Separating the Witnesses 3.Scanning the Scene 4.Seeing the Scene 5.Sketching the Scene 6.Searching for Evidence 7.Securing and Collecting the Evidence

9. Securing the Scene First responding officer’s job #1 SAFETY #2 Preserve evidence –Protect area –Limit exchange –Request team –Logs those that visit

10. Separating the Witnesses 3rd priority; try to prevent collusion –Ask the following questions: When did the crime occur? Who called in the crime? Who is the victim? Can the perpetrator be identified? What did you see happen? Where were you when you observed the crime scene?

11. Scan the scene to determine what photos are needed –May determine primary and secondary crime scene

12. Seeing the Scene Photos of overall area –Close ups w/ and w/out rulers of evidence and bodies Triangulation of stationary objects (reference points) View from different angles and distances

13. Note position of body if applicable and any other evidence Objects measured from 2 immovable landmarks Label N on the sketch and a scale Any objects within the vicinity of crime scene: windows, furniture, doors…. Outside; position of trees, vehicles, shrubs…. Make another final sketch for court Sketching the Scene:

14. Forensic Science: Fundamentals & Investigations, Chapter 2 14 Crime-Scene Sketch Form

17. Searching for Evidence  Depends on number of investigators Walk the scene marking location of evidence, photo, sketch Single investigator: use grid, linear or spiral Group: linear, zone or quadrant pattern Patterns are systematic to ensure no area is left unsearched –Additional light for hair / fibers –Vacuum cleaner –Flashlight and forceps

18. Forensic Science: Fundamentals & Investigations, Chapter 2 18 Crime-Scene Search Patterns

20. Securing and Collecting the Evidence Procedures to package, seal and label –Liquids and arson remains: Airtight, unbreakable container –Biological evidence: Breathable containers to reduce –Mold –DNA degeneration –After dried Paper bindle Plastic/paper bag Evidence tag Signature

21. Evidence Log & Chain of Custody Contains –Case number –Item inventory number –Description of the evidence –Name of the suspect –Name of the victim –Date and Time of recovery –Signature of person recovering evidence –Signature of any witnesses present during collection

22. Forensic Science: Fundamentals & Investigations, Chapter 2 22 Evidence ID Forms

23. Forensic Science: Fundamentals & Investigations, Chapter 2 23 Chain of Custody Maintaining a chain of custody log is essential to present credible evidence in court

24. CHAIN OF CUSTODY Must be maintained to secure evidence 1.Collector finds evidence, bags it in paper or plastic 2.The final container is the collection bag w info 3.Collector’s signature written across sealed edge 4.Taken to a lab and signed over to technician 5.Tech opens bag (tears) somewhere not the sealed edge 6.Technician handles evidence, repackages evidence in original packaging, and then seals in new packaging 7.Sign chain of custody log 8.Ensures responsible handling

25. Analyze Evidence FBI crime is largest forensics lab in the world –Processes all evidence –Each technician has one specialty –Lab results sent to lead detective –Test results lead to crime scene reconstruction Detective tries fit evidence into scenario

26. Crime Scene Reconstruction Hypothetical sequence of events before crime to commission Exam evidence and compare to witness accounts to determine reliability –Evidence does not lie but can be staged

27. Staged Crime Scenes Evidence does not match testimony –Common situations: Arson: Stage fire to cover rubbery, murder Suicide/murder Burglary: Staged to collect insurance money

28. Things to consider when determining staging occurred Initially treat all death investigations as homicide Wounds on victim match weapon? Could the wounds be easily self inflicted? Establish a profile of the victim –Interview friends and family Evaluate the behavior of the victim before the event and the suspects Validate statements with evidential facts Reconstruct the event Determine the facts of the case