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Types of Evidence
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Objectives You will understand:The value of indirect and direct evidence in a
court of law.
That eyewitness accounts have limitations.
What physical evidence can and cannot prove in court.
That the forensic scientist’s main goal is to find a
unique source for the evidence.
You will be able to:Explain the difference between indirect and
direct evidence.
Describe what is meant by physical evidence and give examples.
Distinguish individual evidence from class evidence.
Determine the significance of class evidence.
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5 questions Lawyers should NEVER ask a witness in court:
1. Is it true that you were present until you left the building?
2. Who was it that got killed in the accident - you or your sister?
3. When the two cars collided, how far away from each other were they?
4. Was that the first time that your brother had committed suicide?
5. When he took your photo, were you present?
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Learning TargetsLearning Targets
Distinguish between testimonial and physical evidence.
What factors influence the reliability of eyewitness testimony?
What methods improve accuracy of an eyewitness identifying a suspect correctly?
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Classification of Evidence
Testimonial evidence is a statement made under oath; also known as direct evidence or prima facie evidence.
"at first face" or "at first appearance"
Physical evidence is any object or material that is relevant in a crime; also known as indirect evidence. Examples are hair, fiber, fingerprints, documents, blood, soil, drugs, toolmarks, impressions, glass.
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What kind of evidence is a fingerprint?
Physical
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What kind of evidence is a bitemark?
Physical
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What kind of evidence is
DNA?
Physical
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What kind of evidence is this?
Testimonial Video
Testimonial evidence includes oral or written statements given to police as well as testimony in court by people who witnessed an event.
Eyewitness accounts can be a useful tool in helping investigators with analyzing a crime scene, but are not viewed to be highly reliable. In addition, eyewitness identifications (right or wrong) can have a big influence on the outcome of an investigation or trial.
People are likely to view the same scene in different ways depending on their positions, line of sight, familiarity with the area, and other factors that can interfere with a person’s ability to remember details.
What is testimonial evidence?
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.
Memory Challenge
Types of Evidence
12Neuroscience for Kids - http://faculty.washington.edu/chudler/puzmatch1.html
Items to remember ...
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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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Selective Attention
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Consider the Following
Observe the following image.
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What color was the car to the left of the stop sign?
What type of vehicle was sitting at the right of the stop sign?
What color was the vehicle on the right?
Which way was the stop sign facing?
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Reliability of EyewitnessFalse Memory Experiments
Renowned psychologist Elizabeth Loftus conducted false memory experiments. In this experiment, subjects were shown an image of a car near an intersection.
The researchers asked the subjects who had seen the yield sign questions that deliberately included the words "stop sign." Researchers did the opposite with subjects who were shown the stop sign image.
Results of this experiment showed that subjects created false memories as they recalled not the image they had seen but rather the information that had been implanted.
http://www.ehow.com/info_7935459_forensic-psychology-experiments.html
video
The Bunny Effect
The Bunny EffectCBS News Video
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False Memories (balloon ride)
video
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Video Test
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Jennifer Thompson’s The Innocence Project-CBS 60 Minutes 60 Minutes Part 2
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Reliability of Eyewitness
Factors that affect accuracy:Nature of the offense and the situation in which
the crime is observed
Characteristics of the witness
Manner in which the information is retrieved
Additional factors:Witness’s prior relationship with the accused
Length of time between the offense and the identification
Any prior identification or failure to identify the defendant
Any prior identification of a person other than the defendant by the eyewitness
Innocence Project > 5:23
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According to The Innocence Project (2008) "Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in more than 75% of convictions overturned through DNA testing." Still, the criminal justice system profoundly relies on eyewitness identification and testimony for investigating and prosecuting crimes (Wells & Olson, 2003).
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
Did you know?
What factors affect a person’s memory and their ability to identify a suspect?
Let’s do a little research!
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AgeAge may play a role in the accuracy of an eyewitness’ statement or identification of a suspect. Studies have shown that when a lineup contains the actual culprit, both young children and elderly perform well, but when the lineup does not contain the culprit there is a higher rate of mistaken identifications.
Witness Factors
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
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The racerace of the witness may also play a role. The Cross Race Effect (CRE) is a phenomenon in which people are better at recognizing faces of their own race rather than those of other races.
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The use of drugs can alter a person’s ability to recall the events of a crime even after they are no longer under the influence.
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A person’s memory of an event can be influenced by other witnesses, investigators, and/or the media. Investigators use open-ended questioning and follow procedures for conducting line-ups to limit their influence on a witness’ memory of an event or identification of a suspect.
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A crime that is extremely traumatic for an eyewitness may affect his/her recall of the event.
Ex.: a witness confronted with a weapon tends to focus on the weapon rather than the perpetrator’s face.
Crime Scene & Suspect Factors
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
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Someone who is able to focus on a perpetrator's face for a minute or longer will tend to have a more accurate memory than someone who saw the person for only a few seconds.
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Studies have shown that faces that are either highly attractive, highly unattractive, or distinctive are more likely to be accurately recognized. Simple disguises, such as hats or sunglasses, can interfere with accurate eyewitness identification. However, body piercings and tattoos increases the likelihood of an accurate identification.
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The time of day in which the crime occurred as well as a person’s view of the scene may affect what a he/she is able to see.
In addition, a person who is familiar with the area in which the crime took place, may have a better recall of the positions of the victims or suspects.
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Crime Scene Challenge
Now that your eyes and brain are warmed up, let’s 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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Answer each question below.
1. What color coffee mug was in the picture? Blue Red Yellow 2. When was the deadline? Yesterday Today Tomorrow3. What time was on the clock on the wall? 10:40 11:05 1:55 4. How many sticky notes were on the whiteboard? Four Six Eight5. 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
Source: http://forensics.rice.edu/html/picture_begin.html
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Facial Composites
Investigators work with sketch artists and eyewitnesses to create facial composites, or sketches of a person’s face. Today many police departments are using facial reconstruction software to help them with this task.
The composite may be used internally to assist officers in identifying the suspect or used externally through local media (radio, TV, and newspaper) to solicit leads from citizens.
FACES – A software program that offers many options to help you recreate a person’s facial features.
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Eyewitness
New technology is helping eyewitnesses to be able to describe suspects.
A police composite may be developed from the witness testimony by a computer program or forensic artist.
FACES—a composite program by InterQuest
DEMO
You will need a calculator in a day or two! Make sure you have one. (Was on your supply list)
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Physical Evidence
As a result of the influences on eyewitness memory, physical evidence physical evidence becomes criticalcritical.
Identity and origin of physical evidence is main task of forensic scientist.
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Forensic scientists consider the chemical and physical chemical and physical properties properties of materials they are investigating.
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Physical Properties
Definition: anything you can observe or measure without changing the chemical identity of the substance
Length Shape Color Temperature Density Hardness Solubility [what it
dissolves in] Refractive index [how
substance bends light]
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Physical Changes
Changes in physical properties Chemical composition doesn’t change Tearing a piece of paper Dissolving salt in water Denting your car Spilling milk
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Chemical Properties
Can be observed when the substance changes its chemical composition
Reactivity with :Air (Flammability or oxidizing ability)WaterAcidBase
Sample may be destroyed during testing
VIDEO
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Chemical Changes
Changes in chemical composition;
NEW substance NEW substance MUST be present
Burning Rusting Formation of new gas Formation of new solid Change in pH Growing new cells Digestion
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LET’S LET’S PRACTICE!PRACTICE!
1. Make a T chart (with two headers) on your paper. Physical Changes|Chemical Changes
2. Sort the cards into the two categories.
3. Let me check.
4. Copy the examples into your chart.
5. Practice with the worksheet.
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Work time!
1.Physical vs. Chemical Changes WS
2.Read/highlight back of WS, “Differentiating class and individual evidence”
3.Write a definition for class evidence and for individual evidence in your notebook as summary.
4.Work on witness experiment (plan, create surveys, find video clips or pics, talk to teachers, etc.)
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PHYSICAL EVIDENCE
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If a forensic investigator has just the right evidence, what are some specific facts the evidence could prove? (For example, it can prove that a crime was committed.)
List the following types of evidence in your journal. What do you think each one means? Share with your partner.
Transient evidence Conditional evidence
Circumstantial evidence
Warm up (Think, Pair, Share!):
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Physical Evidence
Is generally more reliable than testimonial evidence
Can prove that a crime has been committed
Can corroborate or refute testimony
Can link a suspect with a victim or with a crime scene
Can establish the identity of persons associated with a crime
Can allow reconstruction of events of a crime
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Physical evidence can be used to answer questions about:
What took place at a crime scene
The number of people involved
The sequence of events
ReconstructionReconstruction
A forensic scientist compares the questioned or unknown sample from the crime scene with a sample of known origin.
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Odors such as perfume, putrification, gasoline, cigarette smoke
Temperature of a coffee pot, car hood, dead body, or water in bathtub
Imprints and indentations such as footprints in sand, fingerprints in dust, teeth marks in perishable foods
Transient evidence is temporary; easily changed or lost; usually observed by the first officer at the scene.
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Conditional evidence is produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event.
Lights on or off?
Garage door up or down?
Door open or closed?
Windows locked or unlocked?
Position of body or furniture?
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Circumstantial evidence implies a fact or event without actually proving it.
More circumstantial evidence = more weight b/c of probability and statistics
Ex: A blond hair is found in the hand of a murder victim having black hair.
(circumstantial—lots of people have blond hair)
Size 11 sneaker print found near by
(circumstantial—lots of people have big feet)
Two observations together limit pool of suspects!
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Probability and Class Evidence Activity
Get out your calculator!
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Can I tell a Blonde joke?
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The local police force was looking for a new detective, so a Blonde went in to interview for the job. Okay, honey, the sheriff asked, “What is 1 and 1?” ” Eleven”, she replied. The sheriff thought to himself, that’s not what I meant, but she’s right. Then the sheriff asked, “What two days of the week start with the letter T?” “Today and tomorrow” she replied. He was again surprised that the Blonde supplied a correct answer that he had never thought of himself. “Now, listen carefully. Who killed Martin Luther King?” Asked the sheriff. The Blonde thought really hard for a minute and finally admitted she had no idea. The sheriff replied, “Well, why don’t you go home and work on that one for a while?” So, the Blonde left and went home. When she walked through the door her husband asked her how the interview went. She replied , “It went great! First day on the job and I’m already working on a murder case!”
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Other EvidencePattern evidence—mostly in the form of imprints, indentations,
striations, markings, fractures, or deposits
Clothing or article distribution
Gunpowder residue
Material damage
Body position
Toolmarks
Modus operandi
Blood spatter
Glass fracture
Fire burn pattern
Furniture position
Projectile trajectory
Tire marks or skid marks
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Significance of Physical Evidence
Individual—can be identified with a particular person or a single source
Blood DNA Typing
Fingerprints
Class—common to a group of objects or persons
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Class vs. Individual Evidence
The large piece of glass fits exactly to the bottle; it is individual evidence.
These fibers are class evidence; there is no way to determine if they came from this garment.
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Class vs. Individual Evidence, continued
Which examples do you think could be individual evidence?
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Forensic Investigations
Include some or all of these seven major activities:
1. Recognition—the ability to distinguish important evidencefrom unrelated material
Pattern recognition
Physical property observation
Information analysis
Field testing
2. Preservation through the collection and proper packaging of evidence
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3. Identification using scientific testing
Physical properties
Chemical properties
Morphological (structural) properties
Biological properties
Immunological properties
4. Comparison of class characteristics measured against those of known standards or controls; if all measurements are equal, then the two samples may be considered to have come from the same source or origin
Forensic Investigations, continued
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5. Individualization in demonstrating that the sample is unique, even among members of the same class
6. Interpretation—giving meaning to all the information
Forensic Investigations, continued
7. Reconstruction of the events in the case
Inductive and deductive logic
Statistical data
Pattern analysis
Results of laboratory analysis
—Henry C. Lee and Jerry Labriola, Famous Crimes Revisited, 2001
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FBI Investigation
Read a case investigated by the FBI. Observe the various units of their lab and read the section: “How Did They Do That?”
www.fbi.gov/kids/6th12th/investigates/investigates.htm
