Forensic Science Fundamentals: Crime Scene Investigation

1. CRIME SCENE INVESTIGATION UNIT 2

2. Before we begin • Automobiles run on gasoline, crime laboratories “run” on physical evidence • Crime laboratories do not solvecrimes… they analyze evidence • Forensic Science is a piece of the total investigative process Forensic Science: Fundamentals & Investigations, Chapter 2

3. The Crime Scene Investigation Team Who is at the crime scene? • Police and possibly a district attorney. • Crime scene investigators. • Evidence Collectors • Detectives • Photographers • Sketchers & Measurers • Specialists • Medical examiners • Entomologists

4. Important vocab to know • Fungible evidence – evidence that is easily mistaken for other evidence • (ketchup for blood) • Transient evidence – evidence that could move or disappear due to weather or time • Modus Operandi – preferred method of operation Forensic Science: Fundamentals & Investigations, Chapter 2

5. The Seven S’s of Crime Scene Investigation • Secure the scene. 1 - Help victims 2 - Arrest perpetrator • Separate the witnesses. • Scan the scene. • See with photos. • Sketch the scene (& measure). • Search for evidence. • “Sack” the found evidence.

6. Packaged evidence is sent to crime lab to be processed Forensic Science: Fundamentals & Investigations, Chapter 2

7. How to Package Evidence • Crease a clean paper and place the evidence in the X position (as shown above). • Fold in the left and right sides, and then fold in the top and bottom. • Put the bindle into a plastic or paper evidence bag affixing a seal over the opening. • Write appropriate info on the bag & your name over the seal.

8. Maintaining Chain of Custody • Forensic Laboratory opens evidence bag creating a new opening in the bag (leaving original opening intact) • Lab processes evidence • Returns evidence to original bag, reseals over new hole with tape signs over tape (legible) • Creates new evid. bag as if the original was the evidence. All info goes on new bag

9. Chain of Custody In order to present credible evidence in court, a chain of custody log is essential. • A person bags the evidence, marks it for identification, seals it, and signs it across the sealed edge (above, left). • It is signed over to a technician in a lab for analysis who opens it, but not on the sealed edge. • After analysis, the technician puts it back in the evidence bag, seals it in another bag, and signs the evidence log (above, right). Forensic Science: Fundamentals & Investigations, Chapter 2

10. What goes where? • AIR TIGHT CONTAINER • Arson evidence (fumes) • STUFF THAT WILL LOOSE ITS QUALITY OVERTIME • BREATHABLE CONTAINER • STUFF THAT CAN GET MOLDY • BLOOD Forensic Science: Fundamentals & Investigations, Chapter 2

11. Analyze the Evidence • The facts of the case are determined when the forensic lab processes all the collected evidence. • The lab then sends the results (lab report) to the lead detective who aims to see how it all fits into the crime scenario. Forensic Science: Fundamentals & Investigations, Chapter 2

12. Analyze the Evidence The lab results can: • Show how reliable are any witness accounts. • Establish the identity of suspects or victims. • Show suspects to be innocent or link them with a scene or victim. Forensic Science: Fundamentals & Investigations, Chapter 2

13. Crime Scene Reconstruction Final step in forensic crime scene invest. Crime scene reconstruction involves: • forming a hypothesis of the sequence of events • Including all events from before the crime was committed through its commission. Forensic Science: Fundamentals & Investigations, Chapter 2

14. Staged Crime Scenes When the lab results do not match up with the testimony of witnesses, it can mean the crime was staged; common examples include: • Staging a fire—to cover bankruptcy. • Staging a suicide—to cover a murder. • Staging a burglary—to collect insurance money. Forensic Science: Fundamentals & Investigations, Chapter 2

15. Staged Crime Scenes To help determine whether a crime scene was staged, consider: • Whether the type of wound found on a victim matches the weapon employed. • Whether the wound could have been easily self-inflicted. • The mood and actions of the victim before the event. • The mood and actions of a suspect before the event. Forensic Science: Fundamentals & Investigations, Chapter 2

16. Kinds of search patterns • Linear • Grid • Quadrant • Spiral • Line

17. Linear search pattern • Good for small evidence Forensic Science: Fundamentals & Investigations, Chapter 2

18. Grid search pattern • Good for finding evidence but easy to get off track Forensic Science: Fundamentals & Investigations, Chapter 2

19. Quadrant search patterns • Good for large areas A B C D E F G 1 2 3 4 5

20. Spiral search Forensic Science: Fundamentals & Investigations, Chapter 2

21. . . . . . . . . . . Summary . . . . . . . . • Locard’s exchange principle: contact between people and objects can transfer material that can determine the nature and duration of the transfer. • Evidence can be direct or indirect (physical or biological traces). • A crime scene investigation team consists of police, detectives, crime scene investigators, medical investigators, and specialists. • The investigation consists of recognizing, documenting, and collecting evidence. Forensic Science: Fundamentals & Investigations, Chapter 2

22. . . . . . . . . . . . . . . . . . Summary • First responding officers identify the extent of the crime scene, secure it, and segregate witnesses. • Crime scene investigators document the crime scene. • Evidence must be collected, packaged, and labeled. • The evidence then is analyzed and interpreted to fit the crime scenario. Forensic Science: Fundamentals & Investigations, Chapter 2