11 August 2014
Evidence is something that tends to
establish or disprove a fact.
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
Direct evidence
Evidence that establishes a fact without the
need for logical inference.
Indirect evidence / circumstantial evidence
Evidence that only provides a basis for
inference about a fact


Direct evidence
Evidence that establishes a fact without the
need for logical inference.
Indirect evidence / circumstantial evidence
Evidence that only provides a basis for
inference about a fact
Example: Having a blood alcohol of 0.12 is direct
evidence for DUI


Direct evidence
Evidence that establishes a fact without the
need for logical inference.
Indirect evidence / circumstantial evidence
Evidence that only provides a basis for
inference about a fact
Example: Leaving a fingerprint at the scene of a
crime is indirect evidence … why?
Direct or Indirect?
 Soil matching a crime location found on a
suspect’s clothing
 Possession of an illegal substance
 Video of a person committing a crime
 Fingerprint at crime scene
 Fingerprints on the murder weapon
 DNA match to skin under victim’s fingernails
Direct or Indirect?
When 
could
youmatching
argue that fingerprints
on the
murder weapon
areon
direct
Soil
a crime
location
found
a evidence?
suspect’s clothing – indirect
When could you argue that fingerprints on the murder weapon are indirect
 Possession of an illegal substance – direct
evidence?
 Video of a person committing a crime - direct
What about skin under the victim’s fingernails? When is it direct? When is it
indirect? Fingerprint at crime scene – indirect
 Fingerprints on the murder weapon – direct?
 DNA match to skin under victim’s fingernails –
direct(?)
** Some people argue that only eyewitness accounts are
direct evidence**



Testimonial evidence - eye witness account
Documentary evidence - records information
relevant to a crime
Example: audio / video / written documents
Physical evidence - any object or material relevant
to a crime
Which type
of evidence?
Which
kind of evidence is best?
 DVD stolen from a store physical
Testimonial
evidence is the most direct (it requires no logical
 Surveillance
video
a robbery
inference),
BUTof
it can
be very unreliable.
documentary
 Crime scene photographs documentary

Most cases of wrongful imprisonment are due
to mistaken eyewitness identification!


Most cases of wrongful imprisonment are due
to mistaken eyewitness identification!
Eye witnesses may be wrong for many reasons:

Age / eyesite / hearing / alcohol or drugs


Most cases of wrongful imprisonment are due
to mistaken eyewitness identification!
Eye witnesses may be wrong for many reasons:



Age / eyesite / hearing / alcohol or drugs
Stress / fear can focus and alter perceptions
Encounters may be brief or take place under poor
conditions


Most cases of wrongful imprisonment are due
to mistaken eyewitness identification!
Eye witnesses may be wrong for many reasons:




Age / eyesite / hearing / alcohol or drugs
Stress / fear can focus and alter perceptions
Encounters may be brief or take place under poor
conditions
New information may alter memories
(It is much more accurate to ask open-ended
questions than leading ones… i.e. ask what the
suspect was wearing, not ‘was he wearing red’.)

Do you know the person who came in?



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If not, what was the age/height/weight/race?
What was he/she wearing?
When did he/she come in?
How long was he/she here?
With whom did he/she speak, and what did
he/she say?
What did he/she knock over?
What did he/she take?
Although circumstantial, physical evidence is
more reliable than eyewitness accounts.
With enough physical evidence, a strong case can
be made.

It can place a suspect at a the crime scene or
with the victim

It can place a suspect at a the crime scene or
with the victim
This is the focus of most investigations.
Based on Locard’s Exchange Principle:
“Every contact leaves a trace”
Every time someone goes some where, they
leave behind physical evidence, and pick up
trace evidence from their environment.

It can place a suspect at a the crime scene or
with the victim
This is the focus of most investigations.
Based on Locard’s Exchange Principle:
“Every contact leaves a trace”
Every time someone goes some where, they
leave behind physical evidence, and pick up
trace evidence from their environment.
Give me an example …



It can place a suspect at a the crime scene or
with the victim
It can help reconstruct a crime (for example,
blood splatter can indicate the relative position
of two people)
Can guide an investigation / indicate that
crime took place (e.g. finding gasoline at a fire
indicates arson)
The more unique or individualized a piece of
evidence is, the better its probative value – the
stronger proof it provides.
Example:
Finding that a suspect has the same brand of duct
tape that was used in a crime is ok evidence.
BUT, if the torn end of the duct tape used in a crime
exactly matches the torn end of the suspect’s role, that
is much better evidence.
Example:
A footprint is found at a crime scene. The
size matches a suspect, but it’s a common
size. How can the print be further
individualized?
Determine whether each type of evidence listed
below is direct or indirect, physical or testimonial.
For physical evidence, also describe additional
details that might individualize the evidence and/or
increase its probative value.

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Survelliance camera videotape of a crime
Written contract
Blood stained clothing
Eyewitness account
Hair found at the crime scene
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What were our objectives and what did we
learn?
How did we address our unit statement?
What was our learner profile trait and how did
we demonstrate it?
1. What is Locard’s Exchange principle?
Classify each of the following as indirect or direct
and as physical, testimonial, or documentary:
2. Boot mark
3. Eye witness account
4. Wire-tap recording
5. Confiscated drugs
Extra credit: what does ‘probative value’ mean?

Evidence Quiz next class!