The Crime Scene

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The Crime Scene

• Chapter 2

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Physical Evidence

• Physical evidence is any object that can
  establish that a crime has been committed or can
  link a crime and its victim or its perpetrator.
• Forensic science begins at the crime scene. The
  investigator must recognize physical evidence
  properly preserve it for laboratory examination.
• The evidence must be kept in its original
  condition as much as possible.

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Securing the Crime Scene

• Secure Isolate the Crime Scene
• First priority is medical assistance to
  individuals arresting the perpetrator.
• Ropes or barricades and guards will prevent
  unauthorized access to the area.
• Every person who enters the crime scene has the
  potential to destroy physical evidence.
• The lead investigator evaluates the scene
  determines the boundaries. They do an initial
  walk through develop a strategy.
• All items must be documented photographed.

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Recording the Crime Scene

• 3 methods of crime-scene recording photography,
  sketches, notes
• Ideally all 3 should be used

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Photography

• The crime scene should be unaltered, unless
  injured people are involved, objects must not be
  moved until they have been photographed from all
  necessary angles.
• If things are removed, added, or positions
  changed the photographs may not be admissible
  evidence.
• Photograph completely
• Area where crime took place adjacent areas
• Various angles

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Photography

• If crime scene includes a body
• Take photos to show bodys location position
  relative to the whole crime scene
• Take close-up photos of injuries weapons lying
  near the body
• After the body is removed, photograph the surface
  underneath.
• When size is significant, use a ruler or other
  measuring scale
• Digital cameras allow for enhancement
  examination in fine detail.
• Videotaping a scene is also becoming popular.

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Sketches

• Once photos are taken, sketch the scene.
• A rough sketch is a sketch, drawn at the crime
  scene, that contains an accurate depiction of the
  dimensions of the scene shows the location of
  all objects having a bearing on the case.
• All measurements are made with a tape measure
• Show all items of physical evidence
• Assign each item a number or letter and list it
  in the legend
• Show a compass heading designating north
• A finished sketch is a precise rendering of the
  crime scene, usually drawn to scale.
• Computer-aided drafting (CAD) has become the
  standard.

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Rough-sketch diagram of a crime scene. Courtesy
Sirchie Finger Print Laboratories, Inc.,
Youngsville, N.C., www.sirchie.com.
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Finished-sketch diagram of a crime scene.
Courtesy Sirchie Finger Print Laboratories, Inc.,
Youngsville, N.C., www.sirchie.com.
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Notes

• Note taking must be a constant activity
  throughout the processing of the crime scene.
• The notes may be the only source of information
  to refresh memory.
• Tape-recording notes at a scene can be
  advantageous detailed notes can be taped much
  faster than they can be written.

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Dealing with Physical Evidence

• Once found, physical evidence must be collected
  stored in a way that preserves its integrity for
  forensic comparison analysis.
• The search for physical evidence must be thorough
  and systematic, even when suspects are
  immediately seized.
• A forensic scientist is not usually needed at the
  scene unless the evidence is complex or it is a
  major crime.
• Some police agencies have trained field evidence
  technicians.

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Searching the Crime Scene

• One person should supervise coordinate.
• Include all probable entry exit points in
  search
• What to search for will be determined by the
  particular circumstances of the crime.
• Examples
• Homicide
• Hit-and-run
• In most crimes, a search for latent fingerprints
  is required.

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Systematic Search
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Collect Physical Evidence

• Physical evidence can be anything from massive
  objects to microscopic traces.
• It may be necessary to take custody of all
  clothing worn by the participants in a crime.
• Handle carefully wrap separately to avoid loss
  of trace evidence.
• Critical areas of the crime scene should be
  vacuumed the sweepings submitted to the lab for
  analysis.
• Mobile crime-scene vehicles carry supplies to
  protect the crime scene photo, collect,
  package evidence develop latent fingerprints.

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Collect Physical Evidence

• The integrity of evidence is best maintained when
  the item is kept in its original condition as
  found at the crime scene.
• The entire object should be sent to the lab.
• If evidence is found adhering to a large
  structure, remove specimen with forceps or other
  appropriate tool.
• In the case of a bloodstain, one may either
  scrape the stain off the surface, transfer the
  stain to a moistened swab, or cut out the area of
  the object containing the stain.

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Collect Physical 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 cross-contamination.

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Autopsy Room

• Medical examiner or coroner carefully examines
  the victim to establish a cause manner of
  death.
• Tissues are retained for pathological
  toxicological examination.
• The following are collected sent to the lab
• Victims clothing
• Fingernail scraping
• Head pubic hairs
• Blood (DNA typing)
• Vaginal, anal, oral swabs (in sex-related
  crimes)
• Recovered bullets from the body
• Hand swabs from shooting victims (for GSR
  analysis)

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Tools for Evidence Collection

• Forceps
• Unbreakable plastic pill bottles w/ pressure lids
• Manila envelopes, glass vials, pill boxes
• Paper bags are better than plasticwhy?
• Fire evidence must be kept in an airtight
  container to prevent evaporation of petroleum
  residues
• Clothing must be air-dried placed in individual
  paper bags.
• http//www.crime-scene.com/ecpi/evidence_collectio
  n.shtml

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Chain of Custody

• Chain of custody is a list of all people who came
  into possession of an item of evidence.
• Chain must be established whenever evidence is
  presented in court as an exhibit.
• Failure to do so may lead to ? Regarding
  authenticity integrity of evidence.
• All items should be carefully packaged and marked
  upon their retrieval at crime sites.
• Normally, the collectors initials date of
  collection are inscribed directly on the article.
• The evidence container must also be marked with
  collectors initials, location of evidence,
  date of collection.

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Standard/Reference Samples

• The examination of evidence often requires
  comparison with a known standard/reference
  sample.
• A standard/reference sample is physical evidence
  whose origin is known, such as blood or hair from
  a suspect, that can be compared to crime scene
  evidence.
• Such materials may be obtained from the victim, a
  suspect, or other known sources.
• The presence of standard/reference samples
  greatly facilitates the work of the forensic
  scientist.

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Standard/Reference Samples

• Bloodstained evidence must be accompanied by a
  whole-blood or buccal swab s/r sample obtained
  from all relevant crime-scene participants.
• A buccal swab is a swab of the inner cheek,
  performed to collect cells for use in determining
  the DNA profile of an individual.
• Some types of evidence must also be accompanied
  by the collection of substrate controls.
• Normally collected at arson scenes.
• A substrate control is uncontaminated surface
  material close to an area where physical evidence
  has been deposited used to ensure that the
  surface on which a sample has been deposited does
  not interfere with laboratory tests.

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Submitting Evidence to the Lab

• Evidence is submitted to the lab either by
  personal delivery or by mail shipment.
• Most labs require that an evidence submission
  form accompany all evidence submitted.
• Enables the lab analyst to make an intelligent
  complete examination of the evidence.
• Provide a brief description of the case history
  so the examiner can analyze in a logical
  sequence.
• The particular kind of examination requested for
  each type of evidence should be delineated.
• A list of all items submitted must be included.

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Death Autopsies

• Forensic Pathology involves the investigation of
  unnatural, unexplained, or violent deaths.
• Forensic pathologists in their role as medical
  examiners or coroners are charged with
  determining cause of death.
• The forensic pathologist may conduct an autopsy
  which is the medical dissection and examination
  of a body in order to determine the cause of
  death.

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Estimating Time of Death

• After a human body expires there are several
  stages of death.
• Rigor mortis results in the shortening of muscle
  tissue and the stiffening of body parts in the
  position at death (occurs within the first 24
  hours and disappears within 36 hours).
• Livor mortis results in the settling of blood in
  areas of the body closest to the ground (begins
  immediately on death and continues up to 12
  hours).
• Algor mortis results in the loss of heat by a
  body (a general rule, beginning about an hour
  after death, the body loses heat by 1 to 1-1/2
  degrees Fahrenheit per hour until the body
  reaches the environmental temperature).

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Other Specialties

• Forensic Anthropology is concerned primarily with
  the identification and examination of human
  skeletal remains.
• Forensic Entomology is the study of insects and
  their relation to a criminal investigation,
  commonly used to estimate the time of death.
• Forensic Psychiatry is an area in which the
  relationship between human behavior and legal
  proceedings is examined.

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Typical blowfly life cycle from egg deposition to
adult fly emergence. This cycle is representative
of any one of the nearly ninety species of
blowflies in North America. Courtesy E. P. Catts,
Ph.D., deceased, and Neal H. Haskell, Ph.D.,
forensic entomology consultant www.forensic-entomo
logy.com.
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Other Specialties

• Forensic Odontology involves using teeth to
  provide information about the identification of
  victims when a body is left in an unrecognizable
  state also investigates bite marks.
• Forensic Engineering is concerned with failure
  analysis, accident reconstruction, and causes and
  origins of fires or explosions.
• Forensic Computer Science involves the
  examination of digital evidence.

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Crime Scene Safety

• The increasing spread of AIDS and hepatitis B has
  sensitized the law enforcement community to the
  potential health hazards that can exist at crime
  scenes.
• In reality, law enforcement officers have an
  extremely small chance of contracting AIDS or
  hepatitis at the crime scene.
• The International Association for Identification
  Safety Committee has proposed guidelines to
  protect investigators at crime scenes containing
  potentially infectious materials that should be
  adhered to at all times.