Friday, September 9, 2011

1. Friday, September 9, 2011 How does new evidence affect what you think happened in a crime? Go Stow! Beat Firestone!

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3. Crime Scene Investigation & Evidence Collection Chapter 2

4. Ch. 2 Crime Scene Investigation and Evidence CollectionBy the end of this Chapter you will be able to: • Summarize Locard’s exchange principle • Identify four examples of trace evidence • Distinguish between direct and circumstantial evidence • Identify the type of professionals who are present at a crime scene • Describe how evidence from a crime scene is analyzed

5. Summarize the three steps of a crime scene investigation • Explain the importance of securing the crime scene • Identify the methods by which a crime scene is documented • Demonstrate proper technique in collecting and packaging trace evidence

6. The Goal of Crime-Scene Investigation To recognize, document, and collect evidence at the scene of a crime.

7. What is a crime? • Crime – An offense against the public at large, proclaimed in a law and punishable by a governing body. • Criminal Law – The body of lawthat, for the purpose of preventing harm to society defines what behavior is criminal and prescribes the punishment to be imposed for such behavior

8. Court Roles

9. Classification of Crimes • Felony – A relatively serious criminal offense punishable by deathor imprisonmentfor more than a year in a state or federal prison • Misdemeanor – Aless serious crime that is generally punishable by a prison sentence of not more than one year in a county or city jail

10. Criminal Investigation • The lawful searchfor people and things to reconstruct the circumstances of an illegal act, apprehend or determinethe guilty party, and aid in the state’s prosecutionof the offender(s).

11. Deductive vs. Inductive Reasoning • Deductive Reasoning: • The drawing ofconclusionsfromlogically related events or observations

12. Deductive vs. Inductive Reasoning • Inductive Reasoning: • The making of inferencesfrom apparentlyseparateobservations or pieces of evidence.

13. The Scientific Method • Formulate a questionworthy of investigation. • Formulate areasonable hypothesisto answer the question. • Testthe hypothesis through experimentation. • Upon validationof the hypothesis, it becomes suitableas scientific evidence.

14. Locard’s Exchange Principle When a person comes in contact with an object or another person, material can be transferred. More intense interactions result in greater exchange. Transferred material is known as trace evidence.

16. Types of Evidence • Direct evidence–Firsthand observations • Examples: eyewitness accounts, video, etc. • Circumstantial evidence–Indirect physical or biological evidence that can link a person to a crime, but don’t directly prove guilt. • Physical examples: bullets, weapons, fibers, tool marks, etc. • Biological examples: body fluids, hair, plant parts, etc.

17. Types of Evidence

18. Explain why this would be or would not be trace evidence

19. Types of Evidence • Class evidence– narrowsan identity to a groupof persons or things. • Example: Paint chip from a blue 1987 Toyota. • Individual evidence– narrowsan identity to a singleperson. • Example: DNA sample

20. Bell Work: 9/11/13 • What is Locard’s Exchange Principle?

21. The Crime-Scene Investigation Team Who is at the crime scene? • Police and … • District attorney (possibly) • Crime scene investigators • Medical examiners • Detectives • Specialists

22. The Seven S’s of Crime Scene Investigation 1. Securing the Scene • Responsibility of the first responder • Restrictsentrance to scene • Starts log of all persons entering • May send for additional experts or officers

23. The Seven S’s of Crime Scene Investigation 2. Separate and question the witnesses • When did the crime occur? • Who called it in? • Who is the victim? • Can the perpetrator be identified? • What did you see happen? • Where were you when you observed the crime scene?

24. The Seven S’s of Crime Scene Investigation • Scanning the Scene • Determine where photosshould be taken • Determine if the location is a primarycrime scene (wherethe crime occurred), or a secondary location (such as where a body was moved).

25. The Seven S’s of Crime Scene Investigation 4. Seeing the Scene • Takephotos, including close-up pictures with and without rulers for scale.

26. The Seven S’s of Crime Scene Investigation • Sketching the Scene • Drawn to scale • All objects should be measured from two immovable objects • Direction of Northshould be included • Scaleof drawing, date, and location should be included.

27. Crime Scene Sketch Form

29. The Seven S’s of Crime Scene Investigation • Searching for Evidence- • Tools such as flashlights, UV lights, or vacuums may be used. • Investigators walk patterns to avoid missing anything

30. Search Patterns

31. The Seven S’s of Crime Scene Investigation 7. Securing and Collecting Evidence – • Liquids and arson remains are stored in airtight, unbreakable containers. • Biologicalevidence is placed in a breathablecontainer to dry.

32. After drying, biological evidence is transferred to a paper bindleand sealed in a bag.

33. Packaging the Evidence • Crease a clean paper and place evidence in the X position • 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 your name on the seal

34. Each different item or similar items collected at different locations must be placed in separatecontainers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

35. Chain of Custody—A list of all persons who came into possession of an item of evidence. • Continuity of possession, or the chain of custody, must be established whenever evidence is presented in court as an exhibit.

36. This means that everyperson who handledor examinedthe evidence and where it is at all times must be accountedfor. • Maintaining a chain of custody log is essential to present credible evidencein court

37. Bag the evidenceAdd identification Seal itSign it across the sealed edge • Sign over to a lab technician Open bag on non-sealed edge • Return items to the evidence bagSeal evidence bag in another bagSign the evidence log

38. Evidence ID Forms

39. Analyze the Evidence After a crime-scene investigation, forensic lab work begins. Test results lead to a crime scene reconstruction. Test results can be used to identify staged crime scenes.

40. Facts result from collected evidence processed by the forensic lab • Lead detective aims to see how factsfit into the crime scenario

41. Lab results can: • Show reliabilityof witness accounts • Establish the identity of suspects or victims • Show suspects to be innocentor link them with a scene or victim

42. Crime Scene Reconstruction Crime scene reconstruction involves: • Forming a hypothesis of the sequence of eventsfrom before the crime was committed through its commission

43. Staged Crime Scenes When lab results don’t match up with the testimony of witnesses Common examples: • Staging a fire—to cover bankruptcy • Staging a suicide—to cover a murder • Staging a burglary—to collect insurance money

44. Was the crime scene staged? Consider: • Does the type of wound match the weapon? • Could the wound be easily self-inflicted? • What were the mood and actions of the victim before the event? • What were the mood and actions of the suspect before the event?