Download Types of Evidence

1. Testimonial evidence; a
statement made under oath by a
witness. Also called direct evidence
or prima facie evidence.
2. Physical evidence; any object or
material relevant in a crime. Also
called real evidence
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.
Items to remember ...
Neuroscience for Kids - http://faculty.washington.edu/chudler/puzmatch1.html
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
What is testimonial evidence?
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.
The Bunny Effect
CBS News Video
Did you know?
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).
What factors affect a person’s memory
and their ability to identify a suspect?
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
Testimonial evidence can often be
faulty. Things that can influence an
eyewitness account:
•Darkness
•Brief encounter
•Stress and fear
•Time between the crime and questioning
•New information, other witnesses accounts
•Leading questions
•TV and newspaper reports
Witness Factors

Age 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.
 The race 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.
 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.
 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.
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
Crime Scene & Suspect Factors
A crime that is extremely traumatic for an eyewitness may affect his/her
recall of the event. For example, a witness confronted with a weapon
tends to focus on the weapon rather than the perpetrator’s face.
 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.
 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.
 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.

Stress and Memory
Source: http://www.helium.com/items/1276135-accurate-eyewitness-accounts
Importance of Forensic Evidence:
Crime Scene 1
Crime Scene 2
Case Example
60 Minutes: Eyewitness
A witness who is physically similar to the offender
is more likely to give an accurate description.
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?
Answer each question below.
1. What color coffee mug was in the picture?
2. When was the deadline?
Yesterday
Blue
Red
Today
3. What time was on the clock on the wall?
Tomorrow
10:40
11:05
4. How many sticky notes were on the whiteboard?
Four
7. What color was the victim's shirt?
Black
8. How many plants were in the picture?
None
Bill
Blue
10. Where was the book in the picture? On a box
Source: http://forensics.rice.edu/html/picture_begin.html
Eight
Trash Can
Brian
Printer
Carl
Red
One
9. What was the color of the marker in the desk drawer?
1:55
Six
5. Which of the following was NOT in the picture? Stapler
6. What was the name on the plaque on the desk?
Yellow
Two
Red
In the trash can
Blue
Green
Under the body
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.
Indirect evidence; provides only a basis for
inference about the disputed fact.
Circumstantial evidence; implies a fact or
event without proving it. The more
circumstantial evidence there is, the greater
weight it carries.
Police or crime scene investigators collect
physical evidence at a crime scene.
Forensic scientists in the lab then determine if
there are links amongCRIME
the victim,
SCENE crime scene,
and suspect.
PERPETRATOR
VICTIM
1. IDENTIFICATION

Determine the PHYSICAL or CHEMICAL
IDENTITY of a substance
2. COMPARISON
COMPARES A KNOWN SAMPLE WITH THAT
OF A QUESTIONED SAMPLE to see if they
have a COMMON ORIGIN (if you can link one
to the other on the triangle).
Known sample
Questioned sample
from crime scene
Good scientific technique demands
that control samples be run as well
to validate the test methods and
procedures.
(1) INDIVIDUAL evidence that can be
related to a single source with an
extremely high degree of probability.
Fingerprints, DNA, handwriting, physical match
(jigsaw fit)
(2) CLASS evidence is associated only
with a group of items that share
similar traits and not necessarily
with a single source.
Glass, hair, fibers
1. The perpetrator was observed to be wearing a
light blue T-shirt. This piece of shirt was found in the
back seat of a suspects car.

Is this piece of blue
T-shirt class or
individual evidence?
This piece of light blue T-shirt was found at the
scene of the crime.
 Are
the two
pieces of shirt
class or
individual
evidence?
2. Are the glass fragments class or individual
evidence that can be uniquely associated with the
broken bottle?
3. The broken bottom half of a bottle was found at
the scene of a crime. The top was found with the
suspect.

Can the top be
uniquely associated
with the bottom?

Explain.
4. This note was found at the bank.
This pad of paper was found in the desk
of a suspect. Can the note be
individualized to the pad?
5. An empty beer can was found at
the scene of a crime.
A case of the same kind of beer
..along with three beer tabs
were found in the suspect’s garage.
 Is
the evidence class or
individual??
 Explain.
6. This shoe print was found at the scene of a hitand-run automobile accident. Witnesses obtained a
description of the car. Explain how a suspects shoe
can be individualized to match a print.
7. Section A of The Bucks County Courier Times
for Tuesday, August 20, 2012 was found at the
scene of a crime.
Section B of the same newspaper was found in
the home of a suspect. Is Section B individual
or class evidence?
8. Powder #1 was found in a baggy in a
suspects pocket.
Powder #2 was found on the victim.
9. Are these cut papers class or
individual evidence? Explain.
10. Are these torn papers class or
individual evidence? Explain.
Posted: Thursday, 21 February 2008 5:13PM

SAN FRANCISCO (KCBS) -- A San
Francisco jury Thursday convicted 74year-old John Puckett for the 1972 rape
and murder of Diana Sylvester. The
Boston native had just gotten her first
job at U.C.S.F. Medical Center when she
was killed in her Inner Sunset District
apartment.
VALUE of the evidence
WHAT ARE THE STATISTICS AND
PROBABILITY ASSOCIATED WITH
THE EVIDENCE?
Puckett insisted he was innocent, saying
that although DNA at the crime scene
happened to match his, it belonged to
someone else.
At Puckett's trial earlier this year, the
prosecutor told the jury that the chance of
such a coincidence was 1 in 1.1 million.

The PRODUCT RULE

¼ of the population has brown hair

½ of the population is male

½ of the population wears jeans

1/3
of the population wears sneakers
What is the probability that
one person is male, has brown hair, is
wearing jeans and sneakers??

¼ of the population has brown hair

½ of the population is male

½ of the population wears jeans

1/3 of the population wears sneakers
THE PROBABILITY RULE:
¼
x
½
x
½
x 1/3 = 1/48 = .0208
Or .0208 x 100 = 2.08 %

How many students at
CR South would be
likely to be male, have
brown hair, and be
wearing jeans and
sneakers??
.0208 x 2100 (current
pop) =
43.75
students
Even Physical Evidence can be wrong…
Extreme care must be taken when collecting and
handling evidence, evaluating evidence, and
presenting evidence. The high standards of the
scientific method try to eliminate all subjectivity, but
as we have just seen…some of the topics that we
will learn about call for some degree of subjectivity.
That is why “expert witnesses” will disagree and
also why many of you may disagree in some of our
labs. It is important to realize that Forensic Science
does not have all the answers and sometimes you
may not be able to build a case using physical
evidence alone. Recognize and understand the
limitations of some of these techniques.