Crime Scene Basics

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Crime Scene Basics
General Science 1 Spring 08
Adapted from T. Trimpe 2006 http//sciencespot.n
et
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Crime Scene Vocabulary

• Crime Scene Any physical location in which a
  crime has occurred or is suspected of having
  occurred.
• Primary Crime Scene The original location of a
  crime or accident.
• Secondary Crime Scene An alternate location,
  such as where additional evidence may be found.
• Suspect Person thought to be capable of
  committing a crime.
• Accomplice Second person associated with
  committing a crime.
• Alibi Statement of where a suspect was at the
  time of a crime.

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Crime Scene Vocabulary

• Chain of custody- the documented and unbroken
  transfer of evidence
• Crime-scene investigation- a multidisciplinary
  approach in which scientific and legal
  professionals work together to solve a crime
• First Responder- the first police officer to
  arrive at a crime scene

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Locards Exchange Principle

• When a person comes into contact with an object
  or another person, a cross-transfer of physical
  evidence can occur.
• The intensity, duration, and nature of the
  materials in contact determine the extent of the
  transfer.
• Fistfight vs. brushing up against someone

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• Evidence used to resolve a crime can be split
  into 2 areas testimonial evidence and physical
  evidence.
• The testimonial evidence would be any witnessed
  accounts of an incident or crime.
• The physical evidence would refer to any material
  items that would be present on the crime scene or
  the victims. These items would be presented in a
  crime investigation to prove or disprove the
  facts of the issue.
• Examples include DNA, the body itself, the weapon
  used, pieces of carpet, blood and other body
  fluids, fingerprints, or casts of footprints or
  tire prints.
• Trace evidence refers evidence that is found at a
  crime scene in small but measurable amounts.

Source http//www3.sc.maricopa.edu/ajs/crime_scen
e_technician.htm
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What will evidence collected at a scene do for
the investigation?

• May prove that a crime has been committed
• Establish any 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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Investigating the Evidence
Forensic Science disciplines at the Illinois
State Police Crime Labs
Drug Chemistry Determines the presence of
controlled substances and the identification of
marijuana Trace Chemistry - Identification and
comparison of materials from fires, explosions,
paints, and glass. Microscopy - Identification
and comparison of hairs, fibers, woods, soils,
building materials, insulation and a broad group
of materials referred to as "particulate
unknowns. Biology/DNA - Presence and comparison
of body fluids and dried stains such as blood,
semen, and saliva. Toxicology Determines the
presence of drugs and poisons in tissue, blood,
urine and other body fluids. Latent Prints -
Identification and comparison of hidden
impressions from sources like fingers, palms,
feet, shoes, ears, lips or the tread on vehicle
tires. Firearms Toolmarks - Examination and
comparison of fired bullets, discharged
cartridges, guns, gunpowder patterns, and marks
left by erased serial numbers in metal or by
burglary tools like a pry bar or
screwdriver. Questioned Documents - Side by side
comparisons of questioned handwriting and hand
printing, ink, paper, writing instruments,
printers, photocopiers, additions, eradications,
obliterations, watermarks, and impressions.
Source http//www.isp.state.il.us/forensics/
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Crime Scene Protocol

• Interview - The first step in processing a crime
  scene begins with interview of 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.
• Examine - The second step in the investigating a
  crime scene, which will help identify possible
  items of evidentiary nature, identify point of
  entry and point of exit, and getting the general
  layout of the crime scene.
• Photograph - The third step in the protocol,
  which involves creating a pictorial record of the
  scene and record items of possible evidence.
  Crime scene photographs are generally taken in
  two categories, overall views and items of
  evidence.
• Sketch - The fourth step in the protocol involves
  drawing a rough sketch to demonstrate the layout
  of the crime scene or to identify the exact
  position of the deceased victim or evidence
  within the crime scene. A crime scene sketch may
  not be completed on every case, however some form
  of sketching usually occurs in most cases, i.e.,
  on a fingerprint lift card to identify exactly
  where the latent was recovered.
• Process 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.

Source http//www.feinc.net/cs-proc.htm