CRIME SCENE INVESTIGATION UNIT 2 1 Before we

CRIME SCENE INVESTIGATION UNIT 2 1

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

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

Important vocab to know l Fungible evidence – evidence that is easily mistaken for other evidence – l l 4 (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

The Seven S’s of Crime Scene Investigation 1. Secure the scene. 1 - Help victims 2 - Arrest perpetrator 2. Separate the witnesses. 3. Scan the scene. 4. See with photos. 5. Sketch the scene (& measure). 6. Search for evidence. 7. “Sack” the found evidence. 5

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

How to Package Evidence 1. Crease a clean paper and place the evidence 7 in the X position (as shown above). 2. Fold in the left and right sides, and then fold in the top and bottom. 3. Put the bindle into a plastic or paper evidence bag affixing a seal over the opening. 4. Write appropriate info on the bag & your name over the seal.

Maintaining Chain of Custody l l 8 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

Chain of Custody 1. 2. 3. 9 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

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

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

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

Crime Scene Reconstruction Final step in forensic crime scene invest. Crime scene reconstruction involves: – – 13 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

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: 14 § 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

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

Kinds of search patterns l l l 16 Linear Grid Quadrant Spiral Line

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

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

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

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

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

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