The Crime Scene

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The Crime Scene

• Chapter 2
• Johnston High School
• Forensics

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Learning Goals

1. Define physical evidence
2. Discuss responsibilities of first officer
   arriving at scene
3. Explain steps to be taken to thoroughly record
   crime scene
4. Describe proper procedures for conducting
   systematic search for evidence

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More learning goals

• 5) Describe proper techniques for packaging
  common types of physical evidence
• 6) Define and understand concept of chain of
  custody
• 7) Understand contributions of the forensic
  pathologist, entomologist, and anthropologist can
  make to a homicide investigation

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Physical Evidence

• Physical Evidence Any object that can establish
  that a crime has been committed or can link a
  crime to its victim or its perpetrator.

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Importance of Evidence

• Forensic Science begins at the crime scene!
• Scientist must be able to RECOGNIZE evidence
• Must be able to COLLECT evidence
• Must be able to PRESERVE evidence
• Remembergarbage in, garbage out!

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Approaching a Crime Scene
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Securing and Isolating Crime Scene

• The first officer at the scene must
• 1) offer medical assistance when needed and/or
  make an arrest
• 2) exclude all unauthorized personnel from scene
  (very hard!)
• 3) Call for assistance/backup
• 4) isolate area (tape, barricades)
• Must try to preserve and protect area as much as
  possible

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Once Secured

• Lead investigator evaluates area
• Determines boundaries
• Establishes perpetrators path (entry and exit)
• Obvious evidence documented and photographed
• Initial walk-through develop strategy for
  examination

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Recording the Scene

• Limited time to work in CS in untouched state
• Records useful for investigation/court
• What are some methods of recording the crime
  scene?

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Recording the Crime Scene

• Photographs
• Sketches
• Notes

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PHOTOGRAPHY

• Take unaltered!
• Do not move evidence until picture is taken!
• If moved, must be recorded in notes
• All photos must show position and location to
  crime scene
• Close ups of smaller items must be taken
• Use a ruler or scale to note size
• Videotaping???

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Photography

• Evidence
• Close ups
• Perspectives
• Multiple angles

• Scene
• Multiple views
• Entrances
• Exits
• Windows

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Sketches

• After photographingmake a rough sketch
• Drawn at crime scene
• Contains accurate depictions of dimensions of
  scene (use tape measurer)
• Shows location of all objects having bearing on
  the case

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Finished Sketch

• Done carefully, attention to appearance
• Must reflect rough sketch (admissible in court)
• Computer Aid Drafting (CAD) -software for
  reconstructing
• Drawn to scale

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Rough Sketch to Final
bsapp.com
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Rough vs Finished Sketch
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Notes

• Match to sketch
• Constant activity
• Quick, short, bulleted
• What can you not see from the photo?
• Helpful for long-term cases - memory
• Identifies all evidence what is it? Who
  collected?
• Tape recording used sometimes

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What should be noted?

• These notes must identify
• Time an item of physical evidence was discovered
• Who discovered it?
• How and by whom it was packaged and marked
• Disposition of an item after it was collected
• May be the only source of information for
  refreshing ones memory

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The Search Part 1

• 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.
• For a factual, unbiased reconstruction of the
  crime, the investigatorrelying upon his or her
  training and experiencemust not overlook any
  pertinent evidence.
• Physical evidence can be anything from massive
  objects to microscopic traces.

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Search Patterns
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The Search Part 2

• Often, most evidence is clearly visible, BUT
• Others can only be detected via examination in
  the lab
• Must collect ALL possible carriers of trace
  evidence
• Clothing
• Vacuum sweepings
• Rug samples
• Fingernail scrapings

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Beyond the Crime Scene

• Search for evidence must extend to autopsy room
• Medical examiner determine COD
• Tissues and organs retained for pathological and
  toxicological examination
• Medical examiner secures a variety of items for
  investigator

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Evidence the ME sends to Investigator

• Victims clothing
• Fingernail scrapings
• Head and pubic hairs
• Blood (for DNA analysis)
• Vaginal, anal, and oral swabs (sex-related
  crimes)
• Recovered bullets from body
• Hand swabs from shooting victims (GSR)

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Interactive Autopsy Assignment

• Go to this website and answer questions (given)
• http//www.hbo.com/autopsy/interactive/
• Click on Interactive Autopsy to the right of the
  screen

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Collecting Packaging Evidence

• Goal handle evidence so that there is least
  amount of change from CS to lab
• Potential problems
• Contamination
• Breakage
• Evaporation
• Accidental scratching/breaking
• Loss via carelessness
• Integrity evidence kept intact (ex. Hair, soil
  should be left on clothing)

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• If evidence is found on large structure (door,
  wall)
• remove specimen with forceps
• With blood, scrape off surface, transfer to
  moistened swab, or cut out area bearing stain

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Most Important Point About Evidence Collection

• Each different item or similar items collected at
  different locations must be placed in separate
  containers!
• Prevents damage through contact
• Prevents cross contamination

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Collecting Evidence

• Bag
• Tag

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Tools for Evidence Collection

• Forceps (to pick up small items)
• Unbreakable plastic pill bottles w/ pressure lids
• Hairs, glass, fibers, other small trace evidence
• Manila envelopes, screw-cap glass vials,
  metal/cardboard pill boxes also good for trace
  evidence

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Small trace evidence and miscellaneous evidence

• Ordinary mailing envelopes should be avoided
• Druggist folds are often used for small trance
• Folding paper to produce closed container,
  keeping specimen inside
• Sealable plastic bags often universal container

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2 Exceptions to the Rule

• Bloodstained materials
• Do NOT store in airtight containers!
• Moisture builds up and allows for mold growth
• Destroys evidentiary value of blood
• Use breathable paper envelopes or bags
• All clothing must be air dried and placed
  individually in separate bags
• Charred debris from a fire MUST be placed in
  airtight container to prevent evaporation of
  volatile petroleum residues

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Chain of Custody

• Chain of Custody a list of all people who came
  into possession of an item of evidence
• Must be established for use in court
• Everyone must be accounted for!
• Each person must obtain written record of
  acquisition and disposition
• Each person may be required to testify in court
• If not, authenticity and integrity of evidence is
  lost

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Collecting Standard/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
• Can also be obtained from victim
• Paint from a hit-and-run vehicle

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Other Controls

• Buccal Swab swab from the inner portion of the
  cheek, performed to collect cells for use in
  determining the DNA profile of an individual
• Substrate Control
• Uncontaminated surface material close to area
  where physical evidence has been deposited
• Used to ensure that the surface on which a sample
  has been deposited does not interfere with lab
  results
• Used in arson cases has surface been exposed to
  accelerant?

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Submit Evidence to Lab

• Delivered personally or by mail depending on case
  and urgency
• Person familiar with case
• Cant ship certain chemicals/live ammo/explosives
• Need evidence submission form
• Nature of crime, victim, case, agency,
  investigator
• Brief description of case
• List of evidence
• What to investigate for each time

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Evidence Submission Form
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Murder Scene Death and Autopsies

• Questions a forensic pathologist may ask
• Who is the victim?
• What injuries are present?
• When did the injuries occur?
• How and why were injuries produced?
• Determining COD is primary role. If not known
  externally, AUTOPSY is performed Medical
  dissection post-mortem to determine COD.

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Review on Estimating TOD

• Rigor Mortis Post mortem condition that results
  in the stiffening of muscle mass
• Manifests within 1st 24 hours disappears within
  36 hours
• Livor mortis Post mortem condition that results
  in the settling of blood in areas closest to
  ground
• Skin appears blue/purplish
• Begins immediately after death and continues for
  up to 12 hours after death
• Was the victims position changed after death?

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Review on estimating TOD

• Algor Mortis Process by which the body
  temperature continually cools after death until
  it reaches the ambient temperature
• Beginning about 1 hour post mortem, body loses
  1-1.5 degrees F per hour
• Rate of heat loss depends on
• Location of body
• Size of body
• Victims clothing
• Weather condition

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Another way to determine TOD

• Determine potassium (K) levels in the ocular
  fluid in the eye (aka vitreous humor)
• After death, cells in the inner surface of
  eyeball release K into ocular fluid
• Use rate of release of K to determine TOD
• Alsofood in stomach last meal

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Forensic Anthropology

• Identification of human skeletal remains
• Bones are extremely durable and undergo slow
  breakdown
• Provide individual characteristics sex, age,
  race, injury
• Create facial reconstruction to help ID
• Help ID in mass disaster

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Forensic Anthropology
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Forensic Entomology