Ch. 2 The Crime Scene Part 1 (pp ) Crime laboratories run on PHYSICAL EVIDENCE!

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Harry Gibbs
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1 Ch. 2 The Crime Scene Part 1 (pp ) Crime laboratories run on PHYSICAL EVIDENCE! Physical Evidence any and all objects that can establish that a crime has or has not been committed or can link a crime and its victim or its perpetrator. Forensic science begins at the crime scene A. Processing the Crime Scene Physical evidence can be class (common to a group of objects or persons) or individual (can be identified with a particular person) Examples: Prints; trace; fluids; bones; weapons; drugs; money; B. Secure and Isolate the Crime Scene From the moment the first police officer arrives at the scene he or she follows a strict set of procedural guidelines designed to protect him and everyone else who s present; guard evidence against damage, contamination, or loss; and document everything that occurs at the scene. A crime scene can be cordoned off using crime scene tape, barricades, automobiles, or even police officers standing guard. Two groups that may be in the way and difficult to move are victim s family members and the press. After the scene is secured, the first officer to arrive establishes a security log which basically is a sign-in sheet that must be signed by any and all visitors. The primary crime scene is where the crime actually occurred. A secondary crime scene is in some way related to the crime but is not where the actual crime took place.

Processing the Crime Scene Physical evidence can be class (common to a group of objects or persons) or individual (can be identified with a particular person) Examples: Prints; trace; fluids; bones;

2 C. Record the Scene: A crime scene may be a single room, an entire house, everything on a property, or even a whole neighborhood. A crime scene investigator begins by doing a walk-through examination, getting a feel for the scene and organizing an approach to collecting evidence. Documentation includes not only the scene and evidence, but also the surrounding area, particularly the perpetrator s possible entry and exit points. HEADING on notes, sketches, etc: Case # Address Date Type of crime (if known) Victim: Investigator: Assisted by: 1. Photography Photographs of the scene need to be taken as soon as possible so that they show the scene preserved in an unaltered condition. Photos must be taken prior to moving or removing any evidence (body). Taking several overview images of the area is a good idea, and if the scene is outdoors, pictures of the surrounding areas should be taken from multiple angles and points of view. Close-ups of each item of evidence are critical. In photos where the size of the object or evidence being recorded is important, the photographer includes a point of reference. A ruler is ideal, but another common object like a pen will work. 2. Sketches Also extremely important, because they show the relationship of each item of evidence to other items or to the body. Each piece of evidence is mapped, or located by its distance from two fixed points, such as a wall, light, or sidewalk. Sketches made at the crime scene may be rough, but they need to be accurate. They can be redrawn for clarity and aesthetics later. Must include proper heading (see above). 3. Notes A designated note taker keeps an accurate account of all activities around the crime scene. Sometimes a tape recorder is used, and the verbal notes are transcribed later. The notes must be detailed, including an overall description of the scene; an accurate list describing what each piece of

Documentation includes not only the scene and evidence, but also the surrounding area, particularly the perpetrator s possible entry and exit points.

3 evidence is; when, where, and by whom it was found; and who transported it to the crime lab. D. Conduct a Systematic Search for Evidence Even when suspects and motive are apparent, the scene must be searched immediately for physical evidence. Area searched depends on: 1. locale and size of area 2. actions of suspect(s) and victim(s) When searching a large area for trace evidence, investigators typically follow a geometric pattern. Four are shown on pg. 53: 1. Spiral, 2. Grid, 3. Linear, and 4. Quadrant. The goal is to carefully search every square inch of the target area.

evidence. Area searched depends on: 1. locale and size of area 2.

4 E. Collect and Package Physical Evidence First: start with evidence that is particularly fragile or that is likely to be lost, damaged, or contaminated, such as blood, fibers, hair, fingerprints, shoeprints, and tire tracks. This method is particularly useful when gathering evidence from outdoor crime scenes, where wind and rain may complicate matters. 1. Fingerprints are photographed and then lifted 2. tool marks and shoe &/or tire marks are photographed then cast 3. fibers and hair are photographed then picked up with tweezers; 4. carpets and furniture are vacuumed, using a fresh vacuum cleaner bag for each area. 5. clothing worn may need to be packaged 6. Bodies some physical evidence is collected during autopsy a. clothing b. fingernail scrapings c. head and pubic hairs d. blood (for DNA typing) e. vaginal, anal and oral swabs f. recovered bullets g. hand swabs from shooting victims (for gunshot residues) Packaging Physical evidence must be protected and packaged separately to avoid damage and cross contamination. a. Small, folded paper in druggist folds, envelopes or paper bags b. Documents are sealed in plastic covers. c. Liquid evidence usually is put into unbreakable, airtight, sealed containers. Clean paint cans and tightly sealed jars work well. (keep volatile evidence from evaporating). d. Moist or wet biological evidence must be placed in non-airtight containers so that they can air dry. Otherwise, the moisture can cause mold, mildew, and bacterial growth which can lead to decay and destroy the sample. e. Bloody clothing is allowed to hang up and dry. Once dry, it can be repackaged into sealed containers.

Fingerprints are photographed and then lifted 2. tool marks and shoe &/or tire marks are photographed then cast 3. fibers and hair are photographed then picked up with tweezers; 4.

5 F. Maintain Chain of Custody Without a continuous record showing that evidence has been kept safe and secure from the crime scene to the lab and ultimately the courtroom, evidence may be rendered inadmissible in court. Every person who handles the evidence must be accounted for and recorded as a link in this unbroken chain of custody, from crime scene to the courtroom. G. Obtain Standard/Reference Samples Control samples are taken from a known source against which the examiner can compare samples taken from the crime scene. Control samples may come from the victim, the suspect, or from items found at the scene. Ex. Hair from persons involved or paint samples from a car involved in an accident, carpet samples a. buccal swab obtained from the inner portion of the cheek used for possible DNA profiling b. substrate control uncontaminated surface material H. Submit Evidence to the Laboratory Each item is to be packaged separately and assigned a number or letter, which should be listed in an orderly and logical sequence on the form. I. Crime-Scene Safety Guidelines put out by International Association for Identification Safety Committee to protect investigators at crime scenes containing potentially infectious materials 1. Wear double gloves and protective shoe covers 2. Wear particle face mask and respirator, goggles or face shield 3. Be alert to sharp objects 4. Use red biohazard plastic bags for disposal of contaminated materials 5. Take notes without contaminated gloves 6. Immediately remove soiled or torn protective equipment then disinfect (10% bleach solution). 7. Eating, drinking, smoking, and makeup are prohibited at the crime scene. 8. All nondisposable items (clothing) put in yellow bag and wash by qualified laundry service.

Obtain Standard/Reference Samples Control samples are taken from a known source against which the examiner can compare samples taken from the crime scene.

6 J. Legal Considerations at the Crime Scene The Fourth amendment to the US Constitution protects citizens against unreasonable searches and seizures which means that police and crime scene investigators need a warrant before they can search for evidence. The steps that are required to obtain a valid search warrant are: 1. Preparing an affidavit this describes the location to be searched, the items to be searched for, and the reasons why the officer expects the items are at that location (probable cause). 2. Preparing the warrant the official document that the judge must sign giving permission for the search to take place 3. Getting the warrant signed the warrant and affidavit go to the judge, who will sign it if he/she feels probable cause exists. Searching without a warrant certain special circumstances allow police to search without a warrant: 1. Emergent situations 2. Impending loss of evidence 3. Lawful arrest 4. Consented search Corpus Delicti = body of the crime : You must prove that a crime occurred before a person can be convicted of committing that crime. i.e. A person cannot be convicted of larceny unless you can prove that property has been stolen. Reasons why people commit a crime: 1.money; 2. revenge; and 3.sex,

Preparing an affidavit this describes the location to be searched, the items to be searched for, and the reasons why the officer expects the items are at that location (probable cause). 2.

C R I M E S C E N E. Forensic Science CC 30.07 Spring 2007 Prof. Nehru

C R I M E S C E N E. Forensic Science CC 30.07 Spring 2007 Prof. Nehru C R I M E S C E N E Physical Evidence Crime laboratories run on physical evidence Physical evidence encompasses any and all objects that can establish that a crime has been committed or can provide a link