crime scene investigation n.
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  2. Goal of Crime Investigation • Find the guilty party. • Exonerate the innocent. • If the investigator doesn’t preserve the evidence or document that preservation correctly, the evidence isn’t useful in court. • Crime Laboratory can’t make the evidence make sense if it isn’t collected correctly

  3. Two Evidence Types • Testimonial evidence is given in the form of a statement under oath in response to questioning. • Physical evidence is anything used, left, removed, altered or contaminated during the commission of the crime, by either the victim(s) or suspect(s).

  4. Physical Evidence • Cannot lie, forget, be mistaken when properly identified, collected and preserved. • Is demonstrable. • Is not dependent on the presence of witnesses. • Is, in some instances, the only way to establish the elements of the crime.

  5. Two Types of Physical Evidence • Individual Characteristics. – A piece of evidence that is unique and can be identified to the exclusion of all others. – Fingerprints – DNA • Class Characteristics – Features shared by all members of a group or class – Footprints

  6. Approach. • Render medical aid. • Identify additional victims or witnesses. • Secure the scene and physical evidence. • Notifications made appropriately.

  7. Approach • Drive carefully‐ Sirens and high speed can be risky. • Scan for suspicious things or persons. • Be alert to evidence, witnesses and victims. • Call for more help and don’t dismiss the help • until the situation is clear.

  8. Rendering Medical Aid • The most important issue is to save a human life or prevent additional injury. • If the crime scene becomes contaminated while rendering aid, that is a price that must be paid. • There aren’t hard and fast rules that can be applied‐ discretion must be used.

  9. Identifying Witnesses/Victims • May need medical attention. • Witnesses identify suspects and locations of additional evidence. • Separate the witnesses so they don’t cross contaminate stories. • Be observant if witnesses give identical stories‐ they may have collaborated before police arrived.

  10. Secure the Scene • Establish a perimeter. – Yellow tape. – Barriers. – Close the door for indoor crimes. – Police officers. • Secure scene and evidence. – Check for exit strategy of the criminal and follow to check for additional evidence.

  11. Secure the Scene • Crime Scene Log is used to document the investigation: – Who entered the scene – Who left the scene – Time In and Out – Reason for entry to the scene • Keep out unauthorized police or fire personnel.

  12. Make Notifications • First Responders notify superiors. • Call in Crime Scene Specialists: – Photo Specialists – Medical Examiners – Crime Scene Units

  13. Types of Scenes • Major Scenes – Homicides – Officer involved shootings – Felonious assaults in which death could occur. – Cases with potential for a major investigation • Non‐major or discretionary

  14. Major Indoor Scenes: Observations and Notes • Time • Entrances and Exits – Doors • Open • Closed • Locked • Type of lock (e.g. deadbolt) • Forced

  15. – Windows • Open • Closed • Locked • Unlocked – Lights (on/off) – Odors • Cigarettes, cigars, perfume, alcohol, gas, gun powder, unusual odors.

  16. Names of Persons at the scene, including emergency personnel. • Condition of the scene: – In disarray/good order – Furniture tossed about – Stains – Position of weapons

  17. Avoid the following: – Do not touch inside doors, doors and door frames. – Do not move anything. – Do not smoke, or use , the telephone, toilet, sink or ashtrays. – Beware where you stand and what you touch. Hold your hand behind your back while surveying the crime scene.

  18. Outdoor Crime Scenes • Establish and protect a large perimeter, especially at parks, beaches or open areas. • If tire/footprint or other impression evidence is found, warn others to stay away. • Try to determine the suspect’s route of approach and escape. • Identify and protect evidence, then collect it. Some evidence is difficult to collect.

  19. Secondary Crime Scenes • Evidence may be located some distance from the original crime scene: – Discarded clothing – Discarded weapons – Blood trails • Protect secondary crime scene evidence as well as primary crime scenes.

  20. Death Cases • Four methods by which death can occur: – Natural Causes – Accidental Death – Suicide – Homicide • Medical Examiner makes this decision.

  21. Death Cases • All death scenes should be treated like a homicide until the medical examiner declares otherwise. • First responders should not hesitate to ask for assistance if needed. Better to err on the side of caution. • Key to a successful investigation is documentation.

  22. Death Cases • Make note of some of the following: – Believability of the witnesses. • Jittery, nervous, anxious to leave the scene? • Does their version of the incident seem questionable? – Condition of the scene. – History of the victim and/or suspect if known. – Preservation of notes or writing for later analysis. – Preserve medications and containers.

  23. Documenting the Crime Scene • Investigators have only a limited amount of time to work a crime site in its untouched state. • Photographs, notes and diagrams document the condition of the crime site and to delineate the location of physical evidence. • Photographs, notes and diagrams prove useful during the subsequent investigation AND are also required for presentation at a trial often months or years later.

  24. Documenting the Crime Scene • A lead investigator will start the process of evaluating the area before collecting evidence. – First, the boundaries of the scene must be determined. – This is followed by the establishment of the perpetrator’spath of entry and exit. – The investigator then proceeds with an initial walk‐through of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.

  25. Crime Scene Search • • The crime scene • coordinator may choose • from a variety of crime • scene search patterns • based upon the type and • size of the crime scene. • • Key is to be orderly and • thorough- don’t walk • over too much but don’t • miss anything.

  26. The Search • • The search for physical evidence at a crime • scene must be thorough and systematic. • • The search pattern selected will normally • depend on the size and locale of the scene • and the number of evidence collectors. • • Physical evidence can be anything from • massive objects to microscopic traces.

  27. Collecting Physical Evidence • • Although much physical evidence is clearly visible, • some may only be detected at the crime laboratory. • – E.g. Semen on sheets after a sexual assault. • • It is important to notice and collect possible carriers • of trace evidence, such as clothing, vacuum • sweepings, and fingernail scrapings, in addition to • more obvious physical evidence. • • Investigators need to keep from contaminating the • evidence‐ e.g. their DNA or fibers.

  28. The Victim Can Provide Evidence • • The search for physical evidence must continue to • the autopsy room of a deceased victim. • • The medical examiner or coroner will carefully • examine the victim to establish a cause and manner • of death. • • Tissues and organs will be retained for pathological • and toxicological examination. • • Also they will provide any physical evidence from the • body of the victim.

  29. Beyond The Crime Scene • The following are often collected and sent to the • forensic laboratory: • 1. Victim’s clothing • 2. Fingernail scrapings • 3. Head and pubic hairs • 4. Blood (for DNA typing purposes) • 5. Vaginal, anal, and oral swabs (in sex related crimes) • 6. Recovered bullets from the body • 7. Hand swabs from shooting victims (for gunshot residue • analysis)

  30. Collecting and Packaging Evidence • • Forceps and similar tools may have to be used to pick • up small items. • • Unbreakable plastic pill bottles with pressure lids are • excellent containers for hairs, glass, fibers, and other • kinds of trace evidence. • • Manila envelopes, screw‐cap glass vials, or cardboard • pillboxes are also good containers • • Ordinary mailing envelopes should not be used • because powders will leak out of their corners.

  31. Packaging to Preserve Evidence • • Each item or similar items collected at different • locations must be placed in separate containers. • • Packaging evidence separately prevents damage • through contact and prevents cross‐contamination. • • The well‐prepared evidence collector will have a • large assortment of packaging materials and tools • ready to encounter any type of situation.

  32. Packaging • • Trace evidence can also be packaged in a carefully • folded paper, using a “druggist fold.” • • Two frequent finds at crime scenes warrant special • attention. • – If bloodstained materials are stored in airtight containers, • the accumulation of moisture may encourage the growth • of mold, which can destroy the evidential value of blood. • – In these instances, wrapping paper, manila envelopes, or • paper bags are recommended.

  33. Obtaining Reference Samples • • Standard/Reference Sample—Physical evidence whose origin • is known, such as blood or hair from a suspect, that can be • compared to crime‐scene evidence. • • The examination of evidence, whether it is soil, blood, glass, • hair, fibers, and so on, often requires comparison with a • known standard/reference sample. • • Although most investigators have little difficulty recognizing • and collecting relevant crime‐scene evidence, few seem • aware of the necessity and importance of providing the crime • lab with a thorough sampling of standard/reference materials.

  34. Evidence Recovery Log • • A chronological record of who found what • evidence, where, witnessed by whom, and • notations about other ways the evidence may • have been documented, e.g., photography