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CRIME SCENE CONTROL - Strongsville City Schools – PowerPoint PPT presentation

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Crime Scenes
  • A crime is the commission or omission of any act,
    which is prohibited or required by the penal code
    of an organized political state, to which some
    punishment or sanction is attached.
  • Classifications
  • Felony
  • Punishable by death or imprisonment for more than
    one year in a state prison (ex murder, rape,
    terrorism, burglary, treason)
  • Misdemeanor
  • Punishable by fine and/or imprisonment for up to
    one year in a local or county jail (ex petty
    theft, disorderly conduct, public intoxication,
    simple assault, vandalism)
  • Infraction or Violation
  • Minor offenses punishable by a fine only (ex
    jaywalking, minor traffic violations, littering,
    disturbing the peace)

The Six Ss of Crime-Scene Investigation
  • A lead investigator/first responder starts the
    process of evaluating the area.
  • Securing the scene
  • Protect the area within which the crime has
  • Separating the witnesses
  • This avoids witness collusion
  • Scanning the scene
  • primary vs. secondary crime scenes
  • Seeing the scene
  • Photograph and triangulate
  • Sketching the scene
  • Rough sketch of all important objects/evidence
  • Searching for evidence
  • In a grid, linear, quadrant, or spiral pattern

Locards Exchange Principle
  • With contact between two items, there will always
    be a transfer of material. The longer or more
    intense the contact, the greater the amount of
    trace evidence present.
  • Wherever he steps, whatever he touches, whatever
    he leaves, even unconsciously, will serve as a
    silent witness against him. Not only his
    fingerprints or his footprints, but his hair, the
    fibers from his clothes, the glass he breaks, the
    tool mark he leaves, the paint he scratches, the
    blood or semen he deposits or collects. All of
    these and more, bear mute witness against him.
    This is evidence that does not forget. It is not
    confused by the excitement of the moment. It is
    not absent because human witnesses are. It is
    factual evidence. Physical evidence cannot be
    wrong, it cannot perjure itself, it cannot be
    wholly absent. Only human failure to find it,
    study and understand it, can diminish its value.

Crime Scene The Beginning
  • Forensic science begins at the crime scene
  • Every forensic investigator has to recognize
    physical evidence and properly preserve it for
    laboratory examination
  • No amount of sophisticated laboratory
    instrumentation or technical expertise can
    salvage the situation if physical evidence is not
    collected properly
  • Crime laboratories run on physical evidence
  • Physical evidence encompasses 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.
  • But if physical evidence is to be used
    effectively for aiding the investigator, its
    presence first must be recognized at the crime

Types of Physical Evidence
  • Blood, semen, and saliva
  • Documents
  • Drugs
  • Explosives
  • Fibers
  • Fingerprints
  • Firearms and ammunition
  • Glass
  • Hair
  • Impressions
  • Organs and physiological fluids
  • Paint
  • Petroleum products
  • Plastic bags
  • Plastic, rubber, and other polymers
  • Powder residues
  • Soil and minerals
  • Tool marks
  • Vehicle lights
  • Wood and other vegetative matter

Categories of Evidence
  • Class Evidence
  • Material that connects an individual or a thing
    to a certain group
  • Individual Evidence
  • Evidence that identifies a particular person or
  • Trace evidence
  • Small or microscopic evidence, or evidence in
    limited amounts
  • Direct Evidence
  • Evidence that provides direct factual information
    in a trial
  • Circumstantial Evidence
  • Indirect evidence used to imply a fact
    incriminate a person
  • Exculpatory Evidence
  • Helps to prove that an accused is not guilty

Crossing Over
  • Crossing over the line from class to individual
    does not end the discussion.
  • How many striations are necessary to
    individualize a mark to a single tool and no
  • How many color layers individualize a paint chip
    to a single car?
  • How many ridge characteristics individualize a
  • How many handwriting characteristics tie a person
    to a signature?
  • These are all questions that defy simple answers
    and are the basis of arguments.

Evidence Recovery
  • Photography
  • The most important prerequisite for photographing
    a crime scene is for it to be in an unaltered
  • Unless there are injured parties involved,
    objects must not be moved until they have been
    photographed from all necessary angles.
  • As items of physical evidence are discovered,
    they are photographed to show their position and
    location relative to the entire scene.
  • After these overviews are taken, close-ups should
    be taken to record the details of the object
  • When the size of an item is of significance, a
    ruler or other measuring scale may be inserted
    near the object and included in the photograph as
    a point of reference.

  • Note taking must be a constant activity
    throughout the processing of the crime scene.
  • The notes must identify
  • the time an item of physical evidence was
  • by whom it was discovered
  • how and by whom it was packaged and marked
  • the disposition of the item after it was
  • The note-taker has to keep in mind that this
    written record may be the only source of
    information for refreshing ones memory.

  • Rough Sketch A draft representation of all
    essential information and measurements at a crime
    scene. This sketch is drawn at the crime scene.
    It shows all recovered items of physical
    evidence, as well as other important features of
    the crime scene
  • Finished Sketch A precise rendering of the crime
    scene, usually drawn to scale. This type is not
    normally completed at the crime scene
  • Unlike the rough sketch, the finished sketch is
    drawn with care and concern for aesthetic

Rough sketch vs. Finished sketch
Crime Scene Search Patterns
  1. Spiral
  2. Strip/Line
  3. Grid
  4. Zone/Quadrant
  5. Pie/Wheel
  • 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 collectors participating in the search.
  • Physical evidence can be anything from massive
    objects to microscopic traces
  • There area a variety of crime scene search
    patterns based upon the type and size of the
    crime scene.

Evidence Recovery Log
  • The evidence recovery log is an important
    document which records all pieces of physical
    evidence found at a crime scene. This is critical
    if the case is to be successfully prosecuted

The Search continued
  • Often, many items of evidence are clearly visible
    but others may be detected only through
    examination at the crime laboratory.
  • For this reason, it is important to collect
    possible carriers of trace evidence, such as
    clothing, vacuum sweepings, and fingernail
    scrapings, in addition to more discernible items.
  • The search for physical evidence must extend
    beyond the crime scene to the autopsy room
  • The medical examiner or coroner will examine the
    victim to establish a cause and manner of death
  • Tissues and organs will be retained for
    pathological and toxicological examination
  • At the same time, arrangements must be made
    between the examiner and investigator to secure a
    variety of items that may be obtainable from the
    body for laboratory examination.

Beyond the Crime Scene
  • The following are to be collected and sent to the
    forensic laboratory
  • 1. Victims 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)

Packaging Evidence
  • Each different item (or similar items) collected
    at different locations must be placed in separate
    containers. Packaging evidence separately
    prevents damage through contact and prevents
  • Each piece of evidence should be packaged
    properly, sealed in an evidence bag, with the
    collectors signature along the taped edge.
  • If bag is opened, cut along non-taped edge and
    reseal and sign when finished.

Obtaining Reference Samples
  • Standard/Reference SamplePhysical evidence whose
    origin is known, such as blood or hair from a
    suspect, that can be compared to crime scene
  • 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.

Evidence in a Court of Law
  • Chain of Custody A list of all persons who came
    into possession of an item of evidence.
  • The chain of custody, if not carefully managed,
    not only increases the risk of contamination, but
    it also can introduce a reasonable doubt
  • Frye Standard (1923)
  • Is the scientific theory/method generally
    accepted in the scientific community?
  • Has the technique been applied correctly?
  • Daubert vs. Merril Dow (1993)
  • Has the scientific theory/technique been tested?
  • Has the scientific theory/technique been subject
    to peer review or publication?
  • Do standards/controls exist, and are they
  • What are the known or potential error rates of
    the theory/technique when applied?

Evidence in a Court of Law-Admissibility
  • Relevance does it relate to this particular case
  • Material evidence must relate to the case at
    hand. Previous criminal records are not
    material, can be prejudicial and are therefore
  • Probativeness evidence must prove something in
    relation to the case.
  • Prejudice anything that unduly affects the
    opinion for or against an accused
  • Statutory Constraints also called privileged
    information, or information told to a person who
    cannot reveal it (clergy, lawyers, etc)
  • Hearsay a statement made outside of court by a
    person not under oath when the statement was made

Evidence in a Court of Law Constitutional
  • 4th Amendment
  • Protects individuals from illegal search and
    seizure. Evidence obtained without a warrant,
    without probably cause, and not listed on a
    warrant is inadmissible regardless of relevance.
    (except in the existence of emergency
    circumstances, need to prevent immediate
    loss/destruction of evidence, consent of the
    parties involved)
  • 5th Amendment
  • Protects individuals from double jeopardy and
    from being tried for a capital crime unless
    indicted by a grand jury
  • 6th Amendment
  • An individuals right to a speedy and public trial
    by an impartial jury
  • 7th Amendment
  • Common law right to a trial by jury
  • 8th Amendment
  • Protection from excessive bail, fines, and cruel
    and unusual punishment

Evidence in a Court of Law Expert Witness
  • Forensic evidence relies on the testimony of
    expert witnesses
  • A person with the appropriate training and
    experience necessary to give valuable information
    pertaining to evidence used in the trial
  • A non-expert is called a lay witness
  • An expert must be qualified as an expert every
    time he/she testifies in court
  • An expert is permitted to offer opinions, whereas
    a lay witness generally cannot

Evidence in a Court of Law
  • Innocent until proven guilty
  • Reasonable Doubt the prosecution has the burden
    of proof. The defense has the responsibility to
    either exonerate the accused, or at least
    introduce a reasonable doubt.
  • The defense must provide a spirited defense,
    regardless of guilt or innocence of the accused
    (or a mistrial can be called)
  • Discovery Motion the defense is required access
    to the witness list, as well as other evidence,
    so that it may carry out its own evaluation of
    the evidence

Case Studies
  • O.J. Simpson-1994
  • Evidence not handled well, leading to
    suggestions it was compromised by dishonest
    criminalists and police.

Outside Nicole Brown-Simpsons home
JonBenet Patricia Ramsey (1990-1996)
JonBenet Ramsey Crime scene wasnt secured and
family friends and father found body,
contaminating the scene