Crime Scene Basics

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Crime Scene Basics
Forensic Science
T. Trimpe 2006 http//sciencespot.net
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Crime Scene Vocabulary

• ______________________________ Any physical
  location in which a crime has occurred or is
  suspected of having occurred.

_________________ CRIME SCENE The original
location of a crime or accident.
_________________ CRIME SCENE An alternate
location where additional evidence may be found.
_________________ Person thought to be capable
of committing a crime.
_______________________ Person associated with
someone suspected of committing a crime.
_____________________ Statement of where a
suspect was at the time of a crime.
Source http//www3.sc.maricopa.edu/ajs/crime_scen
e_technician.htm
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Types of Evidence

• _____________________evidence includes oral or
  written statements given to police as well as
  court testimony by people who witnessed an event.
  
• ______________________ evidence refers to any
  material items that would be present at the crime
  scene, on the victims, or found in a suspects
  possession.
• ______________ evidence refers to physical
  evidence that is found in small but measurable
  amounts, such as strands of hair, fibers, or skin
  cells.

What will evidence collected at a scene do for
the investigation?

• May prove that a crime has been committed
• Establish key elements of a crime
• Link a suspect with a crime scene or a victim
• Establish the identity of a victim or suspect
• Corroborate verbal witness testimony
• Exonerate the innocent.
• Give detectives leads to work with in the case

Source http//www3.sc.maricopa.edu/ajs/crime_scen
e_technician.htm
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Crime Scene Personnel
____________________________________are typically
the first to arrive at a crime scene. They are
responsible for securing the scene so no evidence
is destroyed and detaining persons of interest in
the crime. The ______________________________docu
ments the crime scene in detail and collects any
physical evidence. The _________________________
______is often present to help determine if any
search warrants are required to proceed and
obtains those warrants from a judge. The
___________________________(if a homicide) may or
may not be present to determine a preliminary
cause of death. ________________________
(forensic entomologists, anthropologists, or
psychologists) may be called in if the evidence
requires expert analysis. ____________________
interview witnesses and consult with the CSI
unit. They investigate the crime by following
leads provided by witnesses and physical
evidence.
Source http//science.howstuffworks.com/csi.htm
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Crime Scene Protocol

• Step 1 __________________
• The first step in investigating a crime scene is
  to interview the first officer at the scene or
  the victim to determine what allegedly happened,
  what crime took place, and how was the crime
  committed. This information may not be factual
  information but it will give the investigators a
  place to start.
• Step 2 ________________
• The second step in the investigation of a crime
  scene, which will help identify possible
  evidence, identify the point of entry and point
  of exit, and outline the general layout of the
  crime scene.
• Step 3 ________________
• The third step in the protocol involves creating
  a pictorial record of the scene as well as a
  rough sketch to demonstrate the layout of the
  crime scene and to identify the exact position of
  the deceased victim or other evidence within the
  crime scene.
• Step 4 _______________
• This is the last step in the protocol. The crime
  scene technician will process the crime scene for
  evidence, both physical and testimonial evidence.
  It is the crime scene technicians responsibility
  to identify, evaluate and collect physical
  evidence from the crime scene for further
  analysis by a crime laboratory.

Adapted from http//www.feinc.net/cs-proc.htm
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CORPUS DELICTIBody of the Crime

• You must prove
• that a crime occurred
• that the person charged with the crime was
  responsible for the crime
• Top Reasons for Committing a Crime
• Source of Evidence
• Primary and/or Secondary Crime Scene
• Suspect(s)

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PROCESSING ACRIME SCENE

• Isolate and secure the scene
• Document the scene
• Search for evidence
• Collect and package evidence, maintaining the
  chain of custody
• Submit evidence to the crime lab

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Locards Exchange Principle

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Physical Evidence

• Any object or material found
• As large as building, as small as hairodor and
  submicroscopic like DNA

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Value of Physical Evidence

• Support or reject witness testimony
• Link suspect with victim or crime scene
• Determine identity of people involved in crime
• Allows investigators to re-create crime

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Evidence class or individual?
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Individual Evidence

• Anything that can be linked to a
  unique/individual source
• Ex
• DNA pattern
• Broken glass that fits together

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Class Evidence

• Object has characteristics common to a group of
  objects
• Ex
• Even despite the different sizes, shades, and
  brand
• there are still thousands of pairs just like them
• BUT

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Probative Value

• Definition
• How can you increase probative value of class
  evidence???
• Whats the probative value of class evidence vs.
  individual evidence???

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Step 1

• The first officer to arrive at the scene is
  responsible for securing the crime scene.
• Priorities should be
• Medical assistance for individuals in need
• Arresting the perpetrator
• Exclude all unauthorized personnel from the scene.

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Step 2

• Preliminary Examination
• Photography, sketches, and notes are the three
  methods for crime-scene recording
• Ideally all three should be employed however, as
  is often the case, personnel and monetary
  limitations may prohibit the utilization of some

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Photography

• Must be in an unaltered condition
• 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.
• When the size of an item is of significance, a
  ruler or other measuring scale may be inserted
  and included as a point of reference.

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Sketching in relation to Photography

• A sketch can
• Depict entire scene in one visual whereas a
  photograph cannot
• Be selective eliminate distracting confusion
• Record spatial relationship between items

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Types of Sketches

• Types of Sketches
• _________________
• Most common, overhead view, type we will do
• Cross projection or exploded view
• Cut apart walls like a box lay flat
• _________________
• View from eye level
• Perspective
• 3D photograph-like

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Sketches

• ___________Sketch A draft representation of all
  essential evidence
• information and measurements are taken
• drawn at the crime scene
• Shows all recovered items of physical evidence
• Important features of the crime scene (entry,
  exits, etc)
• ______________Sketch A precise rendering of the
  crime
• drawn to scale
• not normally completed at the crime scene
• drawn with care and concern for aesthetic
  appearance

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Rough sketch should include

• Preparers Name
• Date and Time
• Compass direction
• Objects/evidence
• Measurements of rooms, windows, doors furniture
• Distances between objects, bodies, persons
  entrances/exits
• Key/legend

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Procedure for sketching

• Measure all distances
• Measure walls, windows, door, furniture, people,
  guns, shoe prints, etc.
• __________________
• There are 3 points of measurement item of
  evidence 2 fixed objects
• Triangle is created when measurements are made
  from each of the 2 fixed points to item of
  evidence
• Rectangular Coordinate Measurements
• Measure from 90 degree angle of 2 points

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Notes

• Must be a constant throughout the processing of
  the crime scene
• Should include
• Detailed written description of the scene
• location of items of physical evidence recovered
• Time and by whom evidence was discovered
• How and by whom evidence was packaged

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Importance of Recording

• only a limited amount of time in untouched state
• Opportunity to record original state is key
• Important for
• Investigation

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SEARCH METHODS

• _________________________in large, outdoor scenes
• __________________basically a double-line
  search effective, but time-consuming
• ________________most effective in houses or
  buildings teams are assigned small zones for
  searching
• _________________________best on small, circular
  crime scenes
• ____________________may move inward or outward
  best used where there are no physical barriers

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Search Methods
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The Search

• 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

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Autopsy

• 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.

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Physical evidence collected from body

• Fingernail scrapings
• Head and pubic hairs
• Blood (for DNA typing purposes)
• Vaginal, anal, and oral swabs (in sex related
  crimes)
• Hand swabs from shooting victims(for gunshot
  residue analysis)

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Packaging Evidence

• prevents damage through contact and prevents
  cross-contamination.
• Manilla envelopes, pill bottles, twist on cap
  glass bottles, paper (using ______________)
• If bloodstained materials are stored in airtight
  containers, the accumulation of moisture may
  encourage the growth of mold, which can destroy
  the evidential value of blood.
• In these instances, wrapping paper, manila
  envelopes, or paper bags are recommended
  packaging materials.

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Chain of Custody

• _______________A list of all persons who came
  into possession of an item of evidence.
• Important for court
• Adherence to standard procedures in recording the
  location of evidence, marking it for
  identification, and properly completing evidence
  submission forms for laboratory analysis is
  critical to chain of custody.
• Every person who handled or examined the
  evidence and where it is at all times must be
  accounted for.