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

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Presentation on theme: "Chapter 2 The Crime Scene. Processing the Crime Scene Forensic Science begins at the crime scene Investigators must recognize physical evidence, collect."— Presentation transcript:

1 Chapter 2 The Crime Scene

2 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 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 1.Secure and isolate the crime scene 2.Record the scene 3.Conduct a systemic search for evidence 4.Collect and package physical evidence 5.Maintain a chain of custody 6.Obtain standard/reference samples 7.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 nor 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)

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9 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

10 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

11 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

12 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: 1.Victim’s clothing 2.Fingernail scrapings 3.Head and pubic hair 4.Blood 5.Vaginal, anal and oral swabs (in sex related crimes) 6.Recovered bullets from the body 7.Hand swabs from shooting victims (gunshot residue) Virtual Autopsy http://www.hbo.com/autopsy/swf/casebook2/casebook2.htmlhttp://www.hbo.com/autopsy/swf/casebook2/casebook2.html

13 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.

14 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

15 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.

16 Obtain Standard/Reference Sample Examination often requires comparison with a known standard or reference sample –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

17 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

18 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

19 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

20 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

21 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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