L2 Forensics CrimeScene Investigation and Evidence Collection

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L-2 Forensics Crime-Scene Investigation and
Evidence Collection

• Goal- Recognize, document, collect evidence and
  secure a crime scene.

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Principle of Exchange

• Whenever 2 people come into contact with each
  other, a physical transfer occurs. (Dr. Edmond
  Locards Principle)
• This material that is transferred is called Trace
  Evidence, which can include
• Pet hair/someone else hair on your cloths, brush.
• Fingerprints on a glass
• Soil tracked into a house, business, from a shoe
  or tire
• Drop of blood on a T-shirt
• Paint Chips and Broken glass
• Fibers from clothing, rugs, drapes, bedding, etc.

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Types of Trace Evidence

• Evidence can be classified into two different
  types
• Direct Evidence-
• First hand observations such as eyewitness
  accounts
• In court this would involved testimony by a
  witness who either personally saw, heard or did
  (confessions)

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Types of Evidence Cont.

• Circumstantial Evidence
• Indirect evidence that can only be used imply a
  fact but that does not directly prove it.
• The suspect and the victim are the only ones who
  were involved or witness to what occurred at the
  scene of a crime
• This circumstantial evidence which is (physical
  or biological) found at a crime scene can
  provide a link after examination.

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Physical and Biological Evidence

• Physical evidence are impressions such a
  fingerprints, footprints, shoe prints, lip
  prints, tire impressions, tool marks, weapons,
  bullets and shell casings.
• Physical evidence typically reduces the number of
  suspects to a smaller group of individuals.
  (Fingerprints excluded)
• Biological evidence includes body fluids, hair ,
  plants parts, fibers.
• Biological Evidence narrows the number of
  suspects even more.

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The Crime Scene Investigation Team

• Police officers- Typically the 1st to arrive at a
  scene. DA may also be present for the
  determination of a search warrant.
• Crime Scene Investigators- document in detail,
  collect and record data.
• Medical Examiners- determine cause of death if
  homicide has occurred
• Detectives- look for leads by interviewing
  witnesses and talking to crime scene
  investigators about the evidence
• Specialist- entomologist, forensic scientist,
  psychologist may also be consulted
• All legal and scientific professionals work
  together to solve a crime.

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The Seven Ss of a Crime Scene?

• The Scene is simply defined as the actual site or
  location in which the incident took place.

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Securing the Scene

• It is imperative that the first responding
  officer on the scene protect the individuals
  involved as a first priority.
• Protecting the evidence is the second task. The
  entire investigation could be dependent on this.
  (Bennett- Ramsey)
• Scene is secured by a restricting a perimeter,
  utilizing rope or tape.
• Entry of authorized personal is recorded.
• All unauthorized personal or removed to eliminate
  possibility of contamination or transfer of
  evidence (Locard)
• Typically there is a safe space or comfort
  area which is designated for briefings of
  investigators breaks or storing of equipment.

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Separating the Witness

• Witnesses must not be allowed to talk with each
  other.
• This is done so they do not compare stories and
  so that a new story is not created.
• Questions asked of witnesses?
• When did crime occur?
• Who called in the crime?
• Who is the victim?
• Can the perpetrator be identified?
• What did you see happen?
• Where were you when you observed the crime?

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Scanning the Scene

• A forensic examiner needs to be able to scan the
  scene to determine if there is a primary crime
  scene or potentially a secondary crime scene.
• This is done by the team leader who assumes
  control and assigns other duties such as who will
  be the
• Team Leader
• Photographer
• Log Recorder
• Sketch Artist
• Evidence Recorder and other personnel
• Specialist- entomologist, blood splatter, etc

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Scanning the Scene/Team Leader

• The team leader will make sure team is safely
  equipped and will conduct an initial walk through
• In doing the walk through the leader should
  document conditions of crime scene such as
  lighting (on/off, drapes (open/closed), furniture
  moved, weather, etc.
• It is also important to notice what appears out
  of place or left by an assailient.
• This is all recorded in what is called a
  Narrative Description.

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Narrative Description

• Consist of what is first observed on the initial
  walk through.
• Case should be identified by number, date, time
  location, weather, assignments of team member.
• Condition and position of evidence should be
  noted.
• Clothing described (folds, rolls, condition)
• Describe wounds, bruises, blood spatter.

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Seeing the Scene

• This is done by the photographer
• Photograph overall area from up close and medium
  range using appropriate measurement scales
• Photograph entire area before entered from at
  least two different corners, four is better.
• Photos should show approaching area such as
  street signs, street lams, every room in a house
• Photos should include crowds vehicles, evidence
  latent prints
• Photos also should include victim, eyes, mouth
  hands, maggot activity, etc.

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Sketching the Scene

• An accurate rough sketch drawn to scale noting
  position of evidence and body.
• All objects should be measured from 2 immovable
  landmarks
• Sketch should include Case , date, time,
  locations, and assignments.
• Also included should be dimensions of room,
  furniture, doors, windows, distance of objects or
  bodies from entrances and exits
• Key Legend, should include direction and scale

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Searching for Evidence

• Spiral- circular from outside in and inside out.
• Grid- area divided into north and south, east and
  west strips
• Zone- area usually a room divided into equal size
  zones
• Linear- north and south strips divided, members
  will start at each end and cross

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Searching cont.

• Individual investigators may use zone grid, or
  spiral searches
• A group of investigators will use quadrants,
  linear or zone patterns
• Whichever pattern, all ensure that no area is
  left unsearched
• Flashlight and forceps are important tools

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Search cont.

• Level I Search- 1st completed noting overall
  area. Nothing is touched, the eyes are the only
  tools utilized.
• Level II Search- moving items that cause minimal
  intrusion to the scene. Examples are opening
  closet doors, cabinets, moving heavy furniture.
• Level III Search- most intrusive which includes
  emptying every draw at a crime scene or
  overturning mattress. Also consist of searching
  each pocket the victims cloths or cloths in a
  closet. Carpet or wall or can be taken out.
  (Latent prints and luminal is utilized at this
  stage)

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Securing and Collecting the Evidence

• All evidence needs to be properly packaged,
  sealed, and labeled.
• Liquids and arson remains are stored in airtight
  containers
• Biological evidence is stored in breathable
  contains to dry out and reduce mold. Once dry it
  is placed in a paper bindle, folded and placed in
  a plastic container. Outer containers are sealed

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Collecting Evidence Log

• After each item collected, the packaging must be
  taped and signed.
• All items must be placed on an evidence log for
  purpose of chain of custody.
• Evidence Logs should contain case number,
  inventory numbers, description of evidence, name
  of suspect or victim, date, time and location of
  recovery and quantity.
• Once all evidence has been bagged and labeled, it
  is then placed in a large bag, signed and sealed
  and passed on for purpose of chain of custody.

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Release of Crime Scene

• The following is completed by a team leader
• Review of all aspects of search
• Discussion of findings
• Make sure all evidence is marked and accounted
  for
• Ensure all equipment has been gathered
• Time and date of release and who scene is
  released to.

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Analyzing the Evidence

• Following the crime scene investigation the
  forensic lab work begins
• The FBI crime lab is the largest lab in the world
• Unlike what is on CSI TV shows, forensic lab
  technicians are specialized and process one type
  of evidence
• Results are sent to the lead detective, which
  typically leads to crime reconstruction
• With crime reconstruction, along with statements
  from witness, victims, suspects a hypothesis can
  be formulated which tells of the sequence of
  events that may have occurred from beginning to
  end.

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