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Chapter 08 Chapter 08 Presentation Transcript

  • Physical Evidence Collection and Preservation Chapter 8
  • Objectives
    • Describe steps (including preliminary assessment) to take to protect the scene and preserve evidence
    • Describe the process of identifying evidence
    • Describe the proper process for collecting and preserving evidence
    • Describe the processing of the evidence to include the tagging, analysis, reports, and documentation of the chain of evidence
  • Case Study
    • The cause of a fire was attributed to a light fixture overheating from a tenant covering it with a shirt to block the light
    • A lawyer and a private investigator representing the renters wanted to see the evidence
    • The bulb shown was actually the representative bulb and not the actual bulb
    • The lawyer felt that the investigator was fabricating evidence
  • Introduction
    • It is critical that each department or investigative division establish a physical evidence policy
      • Must cover all aspects of handling and storing evidence for each incident
      • Policy is only as good as those who have input in its creation
      • Everyone within the department must be trained on the policy
  • Authority to Collect Evidence
    • Public assigned fire investigator should collect any and all evidence that would be used as part of a hypothesis
    • If a fire is accidental in nature, there is no crime
      • Must be cautious of unreasonable search and seizure
    • Private investigators and insurance investigators have an entirely different set of rules
  • Protecting Evidence
    • First responders are the first to encounter any evidence on the scene
      • Important to preserve all evidence
    • Overhaul is the process of searching for hidden extension of the fire
    • Salvage is a process of protecting items that have not been damaged
  • Securing a Fire Scene Figure 8-1 Commercial barricade tape can send a clear message to not cross the line.
  • Identifying and Collecting Evidence Figure 8-3 A burn pattern can tell the story of the fire’s origin and direction of travel.
  • Residue Gases and Vapors
    • Vapor density of the gas dictates whether the vapor settles into low areas or rises
      • Most lighter-than-air gases dissipate before a sample can be taken
    • Commercial sampling kits can provide vacuum containers
    • Also can use devices that pull the air sample through a charcoal trap
  • Liquid Samples Figure 8-4 A 1-gallon evidence can with debris should be filled no more than two-thirds to three-quarters full.
  • Solids
    • Solid evidence is sometimes collected for verification of its identity
    • Collecting solids requires precautions
      • Take care not to scoop up different types of solids together
      • Wear double or even triple layers of latex gloves for corrosive materials
  • Finding the Best Sample
    • Leading edge of a floor burn or behind the baseboard that may have protected the accelerant product are both good locations
    • Best “tool” to use to look for evidence is a properly trained K-9 accelerant dog
      • However, using a K-9 does not guarantee a positive sample
  • Evidence Containers Figure 8-6 One-gallon metal paint cans are the containers of choice for most investigators and laboratories.
  • Traditional Crime Scene Forensics Figure 8-7 Tool mark impressions on doors can indicate a forced entry or an attempt by someone to make it look like there was forced entry.
  • Not-So-Traditional Evidence Figure 8-8 Appliances can be involved in the ignition sequence and as such may need to be collected as evidence.
  • Comparison Samples
    • When there are indications of the presence of an accelerant, samples are taken to the laboratory
      • Samples taken from unburned, uncontaminated areas are called comparison samples
        • Electrical switches, electrical circuit breakers, and even electrical panels can all benefit from the collection of comparison samples
  • Contamination
    • Anything introduced into the fire scene or into the evidence that makes test results unreliable
      • Sometimes occurs during suppression activities
    • First responders need to concentrate on protecting what they find
  • Use of Gloves and Safety Gear When Collecting Evidence
    • It is essential that all safety equipment be worn all the time
    • Gloves protect your safety and also help you avoid contaminating any evidence
    • All boots and gear must be thoroughly cleaned between each scene to prevent cross contamination
    • Tools take special care
  • First Responder Considerations
    • Proper training of suppression staff on evidence procedures helps to ensure preservation of evidence
      • If investigator not available, first responder can be trained in evidence collection
    • Chain of custody: method of documenting who had control from collection through trial
  • Documenting, Transporting, and Storing Evidence
    • Documenting Evidence
      • Every piece of evidence collected by the investigator must be tagged or labeled with:
        • Date and time collected, location, person who took it
        • Case number
        • Chain of custody
  • Shipment of Evidence
    • Can personally deliver evidence
    • If a carrier is used:
      • Pack to avoid damage in transit
      • Send registered, requiring a receiving signature
  • Evidence Storage
    • Storage of evidence should be in a secure location where the investigator or lab personnel are the only persons having access
    • Evidence rooms must be climate controlled to keep the environment dry and cool
  • Laboratory Testing
    • Most frequent test requested by fire investigators is the testing of debris for presence of accelerants
    • Common to run two tests together in a method called gas chromatography–mass spectrometry
    • Best tool for success with testing at the laboratory is an open line of communications between lab personnel and fire investigators
  • Release of Evidence
    • Evidence for either a criminal case or a civil suit may have to be kept for years, awaiting trial
    • Not all evidence collected is used in trial
      • Prosecuting attorney decides
    • In civil cases, if the investigator has been subpoenaed, all evidence must be kept the same as if for a criminal trial
  • Summary
    • Evidence consists of a multitude of items from objects to patterns
    • Critical that investigators know legal parameters about taking and securing evidence
    • Once evidence has been collected, it should be locked up and secured
    • Evidence should be processed for testing by a forensic laboratory as soon as practical