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Chapter 2 The Crime Scene

Chapter 2 The Crime Scene. Processing the Crime Scene. Forensic Science begins at the crime scene Investigators must recognize physical evidence, collect the evidence, and properly store and preserve the evidence

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Chapter 2 The Crime Scene

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  1. Chapter 2The Crime Scene

  2. Processing the Crime Scene • Forensic Science begins at the crime scene • Investigators must recognizephysical evidence, collectthe evidence, and properly store and preservethe evidence • Physical Evidence – any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator

  3. Processing a Crime Scene • Secure and isolate the crime scene • Record the scene • Conduct a systemic search for evidence • Collect and package physical evidence • Maintain a chain of custody • Obtain standard/reference samples • Submit evidence to the laboratory

  4. Secure and Isolate the Crime Scene • Responsibility of first officer to arrive on the scene of a crime to preserve and protect the area to the greatest extent possible • First priority is to obtain medical assistance and arrest perpetrator • Next, efforts should be made to exclude all unauthorized personnel and isolate area; every person that enters the scene has potential to destroy evidence • Determine boundaries and establish the perpetrator’s path of entry and exit; crime scene size will depend of locale of scene, size of area, and victims and suspects

  5. Record the Scene • There is a limited amount of time to permanently record the crime scene in its untouched state • Recording the scene is necessary to present in trial and delineate the location of evidence • Three methods of recording a crime scene: • Photography • Sketches • Notes

  6. Record the Crime Scene • Photography • Unless there are injured parties, objects must not be moved until they have been photographed from all angles. If objects are moved, photographs may not be admissible in court – unless recorded in notes. • Items to be photographed: • Area in which the crime took place and all adjacent areas • Points of entry and exit from various angles • If indoors, the entire room and wall area as well as adjacent rooms • A body’s position and close up depicting injuries and near by weapons; once the body is removed, the area under the body should be photographed • Physical evidence position and location as well close up (a ruler or other measuring devise may be used as a point of reference) • Videotaping with sound is also a popular method of recording a crime scene

  7. Record the Scene • Sketches • Rough sketch of the dimensions of the scene showing the location of al objects • The dimensions of objects in the sketch are determined by two fixed point – usually the walls of the room • Finished sketches are usually completed with drafting tools (CAD)

  8. Record the Scene • Notes • Detailed written description of the scene with location of items of physical evidence • Time of discovery of evidence, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collected • Notes may be the only written record to refresh the memory of the investigators • Tape-recording is commonly done

  9. Conduct a Systematic Search for Evidence • Searching the crime scene depends on locale and size of area as well as victims and suspects • Lead investigator will subdivide the scene into segments a search each segment individually or the search may start at some outer point and gradually move toward the center of the scene in a circular fashion

  10. Conduct a Systematic Search for Evidence • Areas searched must include all probable points of entry and exit • Search for evidence will depend on type of crime: • Homicide • Burglary • Vehicular • Kidnapping • Physical evidence can be anything from massive objects to microscopic traces • Some objects may only be traceable in laboratory settings therefore the collection of possible carriers of trace evidence is important • Minute traces of blood on clothing • Hair or fibers in vacuum sweepings

  11. Conduct a Systematic Search • The search for evidence continues in the autopsy of a deceased victim • Medical examiner will determine cause and manner of death and will retain tissues and organs for toxicological and pathological testing • The following should be collected and sent to the forensic lab: • Victim’s clothing • Fingernail scrapings • Head and pubic hair • Blood • Vaginal, anal and oral swabs (in sex related crimes) • Recovered bullets from the body • Hand swabs from shooting victims (gunshot residue)

  12. Collect and Package Physical Evidence • Physical evidence must be handled and processed in a way that prevents any change from the crime scene and the time it is received by the crime laboratory • Changes arise through contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packaging • Whenever possible, evidence should be submitted to the lab intact; blood, hairs, fibers, soil particles should not be removed from articles • Each different item or similar items collected at different locations must be placed in separate containers to prevent damage and cross-contamination.

  13. Examples of packaging containers and techniques: • Plastic pill bottles for hairs, glass, fibers, and other types of small evidence • Manila envelopes or screw-top glass vials for trace evidence (never ordinary envelopes because of possible leaking) • To avoid accumulation of moisture and mold, bloodstained materials should be packaged in manila envelopes or paper bags • Clothing should be air dried and placed in paper bags to allow air flow • Charred debris should be sealed in an airtight container to prevent evaporation • See Appendix I for proper collection and packaging techniques

  14. Maintain Chain of Custody • Chain of custody – continuity of possession must be established whenever evidence is presented in court • Standard procedures include • Recording the location of the evidence • Marking it for id (collector’s initials and date) • Properly completing evidence submission forms for lab analysis • Accounting for every person that handles or examines the evidence.

  15. Obtain Standard/Reference Sample • Examination often requires comparison with a known standardor referencesample • Hit and Run might require paint sample from car to compare to paint at scene • Bloodstained evidence must be compared to blood samples or buccal swaps from all people at the crime scene • Evidence may also be compared to substrate controls– materials adjacent to or close to areas where the evidence has been deposited • If a burned area is suspected to be covered in gasoline, it should be compared to a similar area not suspected • Bloodstains on garments should be compared to area without stains

  16. Submit Evidence to the Laboratory • Evidence is submitted by personal delivery or mail shipment depending on the location of the lab • Evidence submission forms should be completed which provides a brief history of the case, the evidence submitted, and the type of analysis that should be preformed • Analyst not strictly bound to specific test requested if new evidence is found or to search for trace evidence

  17. Crime-Scene Safety • Because of the presence of biological substances with unknown pathogens, care should be taken to avoid contamination and infection • Guidelines set by the International Association for Identification Safety Committee include: • Wear protective gloves, shoe covers, liquid repellent coveralls • Mask/respirators, goggles, or face shields • Evidence possibly containing body fluids should be labeled as biohazard

  18. Legal Considerations at the Crime Scene • The removal of any evidence from a person or from the scene of crime must be done in conformity with the Fourth Amendment – the right against unreasonable searches • There are cases when police can justify a search without warrant

  19. Legal Considerations • Mincey v. Arizona • Undercover police officer, attempting to buy drugs, forced entry into the apartment and was killed • Without a search warrant, police searched the apartment for four days recovering bullets, drugs, and paraphernalia. • Evidence was submitted into trial but since it was illegally seized the court could not convict Mincey

  20. Legal Considerations • Michigan v. Tyler • Loren Tyler and his business partner burned down leased property • Fire officials and police officers searched the premises after the smoke cleared, then 4 days,7 days, and 25 days later to collect evidence • Tyler and partner were convicted but it was overturned as searches were made without warrants (only initial evidence collected at first search was allowed)

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