Types of Evidence

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Types of Evidence

• Coach Whitaker

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Vocabulary

• Evidencesomething that tends to establish or
  disprove a fact
• Testimonial evidencewhat is said in court by a
  competent witness
• Physical evidencetangible items that tend to
  prove some material fact
• Indirect evidenceevidence providing only a basis
  for inference about the disputed fact

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Vocabulary

• Circumstantial evidenceevidence based on
  suggestion rather than personal knowledge or
  observation
• Individual evidencematerial that can be related
  to a single source
• Class evidencematerial that can be associated
  only with a group of items that share properties
  or characteristics
• Probative valuethe ability of evidence to prove
  something that is material to a crime

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Vocabulary

• Unknown samplematerial that has been collected
  from a known location but is of unknown origin
• Known samplematerial that comes from a proven or
  known source

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Evidence

• Evidence is something that tends to establish or
  disprove a fact
• Evidence can be divided into two general types
• Testimonial evidencestatement made under oath
• Physical evidencecan be any object or material
  relevant in a crime

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Testimonial Evidence

• Eyewitness account provides important evidence
  leading to the conviction of a criminal (direct
  evidence)
• Jurors are heavily influenced by testimony
• How accurate are eyewitnesses? What might
  influence their accuracy?

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Testimonial Evidence

• Common eyewitness errors could include
• Crime scene was too dark
• The encounter was too brief
• Presence of a weapon diverted attention
• Stress and fear of the incident
• The time between the crime and questioning
• New information can influence memory

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Testimonial Evidence

• Police need to be careful in judging how reliable
  an eyewitness might besome important points
• The type of crime and how the witness saw it
• Some types of witnesses are better at remembering
  than others
• Interviewing techniques or how info is retrieved
• How the witness knew the accused
• How much time has passed

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Memory Challenge
Directions You will have 30 seconds to view the
next screen. Try to memorize all 20 items you
see! You are NOT allowed to write anything down
You CANNOT talk to anyone else.
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Items to remember ...
Neuroscience for Kids - http//faculty.washington
.edu/chudler/puzmatch1.html
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What do you remember?

• You have 2 minutes to list as many of the items
  as you can!

How did you do? All 20 Awesome 15-19
Great 10-14 Pretty swell 5-9 Could be better
4 or Less Wake up
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Crime Scene Challenge

• Now that your eyes and brain are warmed up, lets
  test your observation skills a bit more.
• You will have 2 minutes to study the photograph
  of a crime scene on the next slide.
• Try to pay attention to details as you will be
  asked 10 questions about the crime scene!
• You are not allowed to write anything down until
  after the time is up.
• Ready?

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(No Transcript)
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Answer each question below.
1. What color coffee mug was in the picture?
Blue Red Yellow   2. When was
the deadline? Yesterday Today
Tomorrow   3. What time was on the clock on the
wall? 1040 1105 155
  4. How many sticky notes were on the
whiteboard? Four Six
Eight   5. Which of the following was NOT in the
picture? Stapler Trash Can
Printer   6. What was the name on the plaque on
the desk? Bill Brian Carl
  7. What color was the victim's shirt?
Black Blue Red   8. How many plants
were in the picture? None One
Two 9. What was the color of the marker in
the desk drawer? Red Blue
Green 10. Where was the book in the
picture? On a box In the trash can
Under the body

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Activity

• Eye witness internet activity
• FACES SKETCH

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Physical Evidence

• A forensic scientist is most interested in
  physical evidence (called real evidence)
• Physical evidence can be any object or
  materialbuilding, odor, hair, DNA etc..
• The variety of physical evidence is unlimited and
  is more reliable than testimonial evidence

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Physical Evidence

• Common types of PE
• Drugs, toxic substances, paints, gunshot residue,
  firearms, impressions, petroleum, alcohols,
  explosive residue, serial numbers, documents,
  fibers, soil, glass, blood, body fluid,
  fingerprints, hair, tissues pollen, wood, bones,
  and tool marks

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Physical Evidence

• Most evidence does not prove a fact and is called
  indirect evidence
• Circumstantial evidenceimplies a fact or event
  without actually proving it
• The more CE there is, the greater weight it
  carries and is based on probability and statistics

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What is the Value of Physical Evidence?

• PE can prove that crime has been committed and
  set the scene for the investigation
• PE can back up witness testimony or prove it
  false
• PE can link a suspect with a victim or with a
  crime scene
• PE can determine the ID of people associated with
  a crime
• Pecan allow investigators to reconstruct a crime
  scene

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Forensic Scientists Role

• The FS must determine if there is a link with the
  evidence and crime and if physical evidence
  collected is relevant to the crime
• An unknown sample is compared to a know sample
• The FS may be apart of a team that reconstructs
  the crime scene

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Individual versus Class Evidence

• The best evidence is anything that can be linked
  to a unique, single source this is called
  individual evidence
• ExamplesDNA, handwriting, fingerprints
• Class evidence is an object that has
  characteristics that is common with a group of
  objects
• Examplesblue jeans, t-shirts,
• An object may have something that individualizes
  it

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Individual versus Class Evidence

• Probative value is the ability of evidence to
  prove something that is material to a crime
  (means supplying proof or evidence)
• Examplesoil and red paint on the jeans together
  would increase the probability that it was apart
  of the crime

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Probability Activity

• Probability and Class Evidence Activity (28-31)

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Trace Evidence

• Trace evidence refers to physical evidence that
• is found in small but measurable amounts, such
• as strands of hair, fibers, or skin cells.

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Locards Exchange Principle
"Every Contact Leaves a Trace"
The Locards Exchange Principle states that "with
contact between two items, there will be an
exchange." For example, burglars will leave
traces of their presence behind and will also
take traces with them. They may leave hairs from
their body or fibers from their clothing behind
and they may take carpet fibers away with them.
Source http//www.virtualsciencefair.org/2004/fre
n4j0/public_html/trace_evidence.htm
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Examples of Trace Evidence

• Paint, Glass, Explosives, Ballistics, Fracture
  Matching, Impressions, Body Fluids, DNA,
  fingerprints, hair, and fibers

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Investigator Tool Kit For Collecting Evidence

• Angle mirror
• Bloodborne pathogen kit
• Body fluid collection kit
• Camera and film
• Chalk
• Compass
• Containers and envelopes
• Scissors
• Screwdrivers
• Sexual assault kit
• Sketching supplies
• Wrecking bar

• Crayon and markers
• Fingerprint kit
• Flashlights
• Knife
• Magnifier
• Measuring tape
• Picks
• Plaster
• Pliers
• Rope or tape
• Spatula
• tweezers

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Common Physical Evidence

• Shoe and tire impressions, tools and tool marks,
  broken glass, soils and minerals, cigarette
  butts, rope and tape, alcohol and drugs, weapons
  and ammo, clothing, hair and fibers, body fluids,
  fingerprints

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Tool Kit

• Make a collage of common tools with a picture of
  each and tell me what you think they are used for