Defining a Crime Scene • There are several ways to classify a crime scene. Type of Crime Location Size
Primary crime scene is the location of the originial criminal activity. This is the original scene. Secondary crime scene is the location after the primary crime scene. This could be where the body was dumped. Classifying according to location This classification does not indicate importance to the scene, but is simply a designation of sequence of locations.
Macroscopic crime scene is composed of many crime scenes. This is the overall or ”big picture” of the crime scene. Microscopic crime scene is more focused on the specific types of physical evidence that is found at the macroscopic crime scenes An example would be trace evidence. Classification based on size
Macroscopic * The body * The body’s wounds * The ground around the body Microscopic * Trace evidence on the body * The gunshot residue around the wound * The tire tread marks in the ground next to the body Gunshot victim's body dumped in a field
Classification based on type of crime committed Robbery Homicide Vandleism Arson Fraud Sexual Assault Kidnapping
Location of crime scene Indoors Outdoors Vehicle River
Eight types of information that can be obtained from the examination of the physical evidence found at the crime scene Information on the Corpus Delicti Information on the Modus Operandi Linkage of Persons, Scenes, and Objects Proving or Disproving Witness Statements Identification of Suspects Identification of Unknown Substances Reconstruction of a Crime Providing Investigative Leads
Information on the Corpus Delicti Determination of the essential facts of an Investigation. *Physical evidence *Patterns of evidence *Lab examination of the evidence
Information on the Modus Operandi Criminals repeat their behavior and certain behavior becomes their “signature” Vocabulary term: Modus Operandi
Linkage of Persons, Scenes, and Objects Physical evidence can accomplish establishing the linkage between the suspects and the victims. This is the most important and most common type of linkage. Vocabulary term: Locard’s Exchange Principle
Suspect Victim Physical Evidence Object Crime Scene
Proving or Disproving Witness Statements Credibility is an important issue with witnesses, suspects, and victims. Credibility can be determined by crime scene patterns or patterned physical evidence.
Patterned physical evidence Bloodstain interpretation Latent Fingerprints Gunshot Residue Bloodsplatter
Identification of Suspects This process is accomplished by the first three steps in a crime scene investigation (recognition, identification, and individualization) Vocabulary terms: AFIS CODIS
Identification of Unknown Substances Bacteria Drugs Poisons Anthrax
Reconstruction of a Crime Final step in the forensic examination process. The “how” of the crime scene is more important than the “who.”
Providing Investigative Leads Physical evidence can provide directional leads to an investigator. *Not all physical evidence at a crime scene will be directly linked to a suspect.
Steps to the scientific examination of a crime scene • Recognition • Scene survey • Documentation • Collection and preservation • Identification • Comparison testing • Individualization • Evaluation • Interpretation • Reconstruction • Reporting and presentation
Crime Scene Management Information Management Manpower Management Technology Management Logistics Management
Duties of First Responding Officer • Assist the victim. • Search for and arrest the suspect if still on the scene. • Detain all witnesses. • Protect the crime scene. • Note and communicate to crime scene investigators all movements and alterations made to the crime scene.
Science at a Crime Scene FYI: There may be more than one hypothesis for a given set of facts.
Securing the Crime Scene Level 1: Overall scene security for restriction of general public. ****To prevent changing or alteration of the scene—Contamination. Level 2: Restriction to Official business Level 3: Target area
Crime Scene Survey • Walk-Through : Preliminary crime scene survey performed to orient the crime scene investigator to the scene and the physical evidence at the scene.
Guidelines to follow in a walk-through • Use the walk-through to mentally prepare a reconstruction theory that can and should be changed as the scene investigation progresses. • Note any transient (temporary) or conditional (the result of an action) evidence that requires immediate protection and processing. • Be aware of weather conditions and take precautions. • Note all points of entry or exit and paths of travel within the scene. (Be aware of alteration or contamination made by the first responder) • Record initial observation of who, what, where, when, and how • Assess the scene for personnel, precautions, or equipment that will be needed.
Crime Scene Documentation • Take notes at the crime scene. • Videotape the crime scene. • Photograph the crime scene. • Sketch the crime scene.
Taking notes • Provides a written record of all of the crime scene activities. • Taken as activities are completed.
Videotaping • Gives a three-dimensional portrayal of the scene. • Should follow the scene survey.
Photographing • Provides a true and accurate pictorial record of the crime scene and physical evidence present. • MAKE SURE YOU WRITE DOWN THE GUIDELINES FOR PHOTOGRAPHY ON PAGE 175.
Sketching • The assignment of units of measurement or correct perspective to the overall scene and the relevant physical evidence identified within the scene. • Three techniques to obtain measurements: triangulation, baseline, polar coordinates
Triangulation: method of measurement of a crime scene and physical evidence; every item of evidence is measured from two fixed points. • Baseline: method for measuring a crime scene and the evidence present; after a fixed line is identified, the items of evidence are measure from that line at right angles. • Polar coordinates: method of crime scene measurement; measurement of items of evidence based upon their distances and angles from a fixed position.