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Chapter 08


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Chapter 08

  1. 1. Physical Evidence Collection and Preservation Chapter 8
  2. 2. Objectives <ul><li>Describe steps (including preliminary assessment) to take to protect the scene and preserve evidence </li></ul><ul><li>Describe the process of identifying evidence </li></ul><ul><li>Describe the proper process for collecting and preserving evidence </li></ul><ul><li>Describe the processing of the evidence to include the tagging, analysis, reports, and documentation of the chain of evidence </li></ul>
  3. 3. Case Study <ul><li>The cause of a fire was attributed to a light fixture overheating from a tenant covering it with a shirt to block the light </li></ul><ul><li>A lawyer and a private investigator representing the renters wanted to see the evidence </li></ul><ul><li>The bulb shown was actually the representative bulb and not the actual bulb </li></ul><ul><li>The lawyer felt that the investigator was fabricating evidence </li></ul>
  4. 4. Introduction <ul><li>It is critical that each department or investigative division establish a physical evidence policy </li></ul><ul><ul><li>Must cover all aspects of handling and storing evidence for each incident </li></ul></ul><ul><ul><li>Policy is only as good as those who have input in its creation </li></ul></ul><ul><ul><li>Everyone within the department must be trained on the policy </li></ul></ul>
  5. 5. Authority to Collect Evidence <ul><li>Public assigned fire investigator should collect any and all evidence that would be used as part of a hypothesis </li></ul><ul><li>If a fire is accidental in nature, there is no crime </li></ul><ul><ul><li>Must be cautious of unreasonable search and seizure </li></ul></ul><ul><li>Private investigators and insurance investigators have an entirely different set of rules </li></ul>
  6. 6. Protecting Evidence <ul><li>First responders are the first to encounter any evidence on the scene </li></ul><ul><ul><li>Important to preserve all evidence </li></ul></ul><ul><li>Overhaul is the process of searching for hidden extension of the fire </li></ul><ul><li>Salvage is a process of protecting items that have not been damaged </li></ul>
  7. 7. Securing a Fire Scene Figure 8-1 Commercial barricade tape can send a clear message to not cross the line.
  8. 8. Identifying and Collecting Evidence Figure 8-3 A burn pattern can tell the story of the fire’s origin and direction of travel.
  9. 9. Residue Gases and Vapors <ul><li>Vapor density of the gas dictates whether the vapor settles into low areas or rises </li></ul><ul><ul><li>Most lighter-than-air gases dissipate before a sample can be taken </li></ul></ul><ul><li>Commercial sampling kits can provide vacuum containers </li></ul><ul><li>Also can use devices that pull the air sample through a charcoal trap </li></ul>
  10. 10. Liquid Samples Figure 8-4 A 1-gallon evidence can with debris should be filled no more than two-thirds to three-quarters full.
  11. 11. Solids <ul><li>Solid evidence is sometimes collected for verification of its identity </li></ul><ul><li>Collecting solids requires precautions </li></ul><ul><ul><li>Take care not to scoop up different types of solids together </li></ul></ul><ul><ul><li>Wear double or even triple layers of latex gloves for corrosive materials </li></ul></ul>
  12. 12. Finding the Best Sample <ul><li>Leading edge of a floor burn or behind the baseboard that may have protected the accelerant product are both good locations </li></ul><ul><li>Best “tool” to use to look for evidence is a properly trained K-9 accelerant dog </li></ul><ul><ul><li>However, using a K-9 does not guarantee a positive sample </li></ul></ul>
  13. 13. Evidence Containers Figure 8-6 One-gallon metal paint cans are the containers of choice for most investigators and laboratories.
  14. 14. 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.
  15. 15. 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.
  16. 16. Comparison Samples <ul><li>When there are indications of the presence of an accelerant, samples are taken to the laboratory </li></ul><ul><ul><li>Samples taken from unburned, uncontaminated areas are called comparison samples </li></ul></ul><ul><ul><ul><li>Electrical switches, electrical circuit breakers, and even electrical panels can all benefit from the collection of comparison samples </li></ul></ul></ul>
  17. 17. Contamination <ul><li>Anything introduced into the fire scene or into the evidence that makes test results unreliable </li></ul><ul><ul><li>Sometimes occurs during suppression activities </li></ul></ul><ul><li>First responders need to concentrate on protecting what they find </li></ul>
  18. 18. Use of Gloves and Safety Gear When Collecting Evidence <ul><li>It is essential that all safety equipment be worn all the time </li></ul><ul><li>Gloves protect your safety and also help you avoid contaminating any evidence </li></ul><ul><li>All boots and gear must be thoroughly cleaned between each scene to prevent cross contamination </li></ul><ul><li>Tools take special care </li></ul>
  19. 19. First Responder Considerations <ul><li>Proper training of suppression staff on evidence procedures helps to ensure preservation of evidence </li></ul><ul><ul><li>If investigator not available, first responder can be trained in evidence collection </li></ul></ul><ul><li>Chain of custody: method of documenting who had control from collection through trial </li></ul>
  20. 20. Documenting, Transporting, and Storing Evidence <ul><li>Documenting Evidence </li></ul><ul><ul><li>Every piece of evidence collected by the investigator must be tagged or labeled with: </li></ul></ul><ul><ul><ul><li>Date and time collected, location, person who took it </li></ul></ul></ul><ul><ul><ul><li>Case number </li></ul></ul></ul><ul><ul><ul><li>Chain of custody </li></ul></ul></ul>
  21. 21. Shipment of Evidence <ul><li>Can personally deliver evidence </li></ul><ul><li>If a carrier is used: </li></ul><ul><ul><li>Pack to avoid damage in transit </li></ul></ul><ul><ul><li>Send registered, requiring a receiving signature </li></ul></ul>
  22. 22. Evidence Storage <ul><li>Storage of evidence should be in a secure location where the investigator or lab personnel are the only persons having access </li></ul><ul><li>Evidence rooms must be climate controlled to keep the environment dry and cool </li></ul>
  23. 23. Laboratory Testing <ul><li>Most frequent test requested by fire investigators is the testing of debris for presence of accelerants </li></ul><ul><li>Common to run two tests together in a method called gas chromatography–mass spectrometry </li></ul><ul><li>Best tool for success with testing at the laboratory is an open line of communications between lab personnel and fire investigators </li></ul>
  24. 24. Release of Evidence <ul><li>Evidence for either a criminal case or a civil suit may have to be kept for years, awaiting trial </li></ul><ul><li>Not all evidence collected is used in trial </li></ul><ul><ul><li>Prosecuting attorney decides </li></ul></ul><ul><li>In civil cases, if the investigator has been subpoenaed, all evidence must be kept the same as if for a criminal trial </li></ul>
  25. 25. Summary <ul><li>Evidence consists of a multitude of items from objects to patterns </li></ul><ul><li>Critical that investigators know legal parameters about taking and securing evidence </li></ul><ul><li>Once evidence has been collected, it should be locked up and secured </li></ul><ul><li>Evidence should be processed for testing by a forensic laboratory as soon as practical </li></ul>