Transcript Presentation

Chapter 2
Importance of Evidence
Physical Evidence

Any material present at the crime scene, on the
victims, or the suspect.

Can be at primary or secondary crime scene.
Physical Evidence

What will physical evidence found at the crime
scene do for the investigation?
May prove that a crime has been committed
 Establish key elements for 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 a case

Trace Evidence

Refers to physical evidence that is found in small
but measureable amounts.

Examples include:
Strands of hair
 Fibers
 Skin cells

Testimonial Evidence

Oral or written statements given to police as well
as court testimony by people who witnessed an
event.

Can include court testimony by people who
witnessed an event.

Testimony from _________ witnesses is very
important in court.
Class vs. Individual Characteristics

Determining whether evidence is from a group
or a specific source is crucial in investigations.

These associations may help investigators
determine a link between the crime scene,
parties involved, and/or the evidence.
Class Characteristics

Recurring characteristics shared by one or more
objects in a group.

All objects in this group will have the exact same
characteristics.
Ch. 2 Sec. 1 Notebook Quiz






1) What is physical evidence?
2) What can physical evidence found at a crime
scene do for the investigation?
3) Define and give 3 examples of trace evidence.
4) What is testimonial evidence?
5) Determining whether _____ is from a
_______ or specific source is _____ in _____.
6) What is the difference between class and
individual characteristics?
Example




All size 10 Nike Air Force size 10 shoes are
manufactured to have a particular design.
All will have the same general appearance.
This is what distinguishes it from other shoes.
If we find this print at a crime scene, it will tell
us the type of shoe but not the person who
owns it.
Individual Characteristics

Random, unique features of an object that set it
apart from other objects with the same class
characteristics.

All objects in the same group will not have the
same individual characteristics.
Example
Continuing with the footwear theme: cuts
scratches, abrasions, foreign objects (rocks), not
general wear, etc.
 These characteristics are unique to 1 and only 1
particular shoe.
 Individual characteristics are
very important pieces of
evidence.

Class vs. Individual Characteristics
Activity
1)
2)
3)
4)
5)
6)
7)
Tire track
8) Duct tape
Blue hat
9) Baseball bat
Social security card
10) License plate
Human skin cells
11) Fingerprint
# 2 Pencil with bite marks 12) Extension cord
Empty Advil bottle
13) Nike Air shoeprint
.22 Rifle bullets (unfired) 14) Blood droplet
Forensic Vocabulary




Motive: the cause that induces people to
complete a certain action
Intent: the design or purpose to commit an act
Catalyst: substance that accelerates a chemical
reaction
Conclusive evidence: evidence that may not be
disputed and must be accepted by the court as a
definitive fact
Forensic Vocabulary




Fingerprint: unique patterns created by skin ridges
found on the palm sides of fingers and thumbs
Gene: unit of inheritance consisting of a sequence of
DNA
Indicator: chemical used to determine the presence of
an acid or a base
Microscopic hair analysis: procedure of examining
hair shafts for identifiable characteristics
Forensic Vocabulary




Chromatography: process of separating a
chemical mixture into individual substances
Composite drawing: sketch of a suspect
produced from one or more eyewitnesses
Criminology: study of criminal activity and
how it is dealt with by the law
DNA profiling: process of testing to identify
DNA patterns or types
Intro. To Forensic Anthropology




Anthropology: study of humans, past and
present
In forensics, it is studying the remains of
humans in order to help solve a crime.
How can studying remains of humans be
helpful in a forensic investigation?
What things can be learned from studying
skeletal remains?
Case Study # 9

A robbery has occurred at 1216 E. Main St. The
front glass window was discovered broken and
all inventory has been stolen. Small blood
droplets were discovered on the sidewalk outside
of the store. No blood was discovered inside the
store. There were no cameras inside the store.
No fingerprints or other pieces of evidence
were found. Based on this information, answer
the following questions:
Case Study # 9: Review Questions





1) What evidence was present?
2) Can you solve the crime based on this evidence?
Why or why not?
3) List 2 things that this evidence can tell you about the
suspect. Why is this important?
4) Which is more useful in blood evidence: DNA
Sequence or Blood Type? Why?
5) Is there anything suspicious about finding the blood
evidence on the outside instead of the inside of the
store?
Case Study # 11

Police receive a letter from an 8 year old girl that
goes by Lauren. Lauren has been missing for 3
weeks. It had been presumed that she was
kidnapped because on the day she went missing,
her dad was released from prison. In the letter, the
girl states that she is fine and requests that police
call off the search for her. It also states that she
has found a new home where she will be taken care
of. The entire letter is written in cursive, contains
no grammatical errors, and is signed Ellie (her first
name that no one calls her).
Case Study # 11: Review Questions





1) Why was it presumed that Lauren was
kidnapped?
2) Who is the prime suspect in the crime?
3) What is suspicious about the way the letter is
written?
4) What is suspicious about the way the letter is
signed?
5) How could investigators verify that this is
indeed Lauren’s handwriting?
Case Study # 12

A robbery has occurred at the First National
Bank in Bloomington, Indiana. 2 masked men
entered the bank at 9:00 A.M. carrying pistols
and empty bags. They forced all customers and
employees onto the ground upon entering. After
collecting the money, one of the men dropped
his wallet containing his social security card.
Suspect # 2 took off his mask when exiting the
bank and his face was captured on camera.
Case Study # 12: Review Questions





1) Where did the crime take place?
2) What type of crime has occurred?
3) List the pieces of evidence that were found as
well as if each has class or individual
characteristics.
4) How can the evidence be used to locate the
suspects?
5) Were there any witnesses? If so, how would
they be useful in solving this case?