Chapter 8 – Crime and
Criminal Law
Unit 3 – Criminal Law
Crime Scene Investigation
Learning Goal for Today
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By the end of the lesson(s), students will
be able to discuss police investigative and
evidence gathering techniques
Expectations
By the end of this lesson, students will:
…explain the processes of police
investigation, arrest, search, and
interrogation of suspects
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Agenda
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Crime Scene Investigation
Fingerprints
Trace Elements
Gunshot Residue
DNA
Introduction
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Chain of events from crime to trial is
subject to the laws of criminal procedure
Laws balance two sometimes conflicting
objectives: to discover the truth about a
criminal event and to protect civil liberties
Rules of criminal procedure mark the
boundary between legitimate police
investigative practices and a person’s right
to liberty, privacy and personal security
Introduction (Cont’d)
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Reflect the belief that state power should
be limited
That the rule of law applies as much to
police as to people accused of crimes
That the ends do not always justify the
means
Charter of Rights and Freedoms confirms
our commitment to fair process making
criminal procedure a matter of
constitutional law
Crime Scene Investigation
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Investigation and evidence collection and
securing of evidence huge responsibility
Lapses can derail a trial or result in a
miscarriage of justice
Crime scene is a rich source of evidence
Crime scene has boundaries
Accidental contamination is an concern
Crime Scene
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Protect the area from accidental or
intentional contamination by anyone,
including police officers and other official
personnel
s.129 of the Code, obstructing a police
officer in the lawful execution of his/her
duties; gives police authority to cordon off
and refuse entry to a crime scene
Crime Scene Investigation
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Officer in charge of investigation
determines when crime scene may be
safely returned to public access
Crime Scene Investigation
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Security of the scene falls under the
coroner’s authority in the following cases:
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Sudden or unexpected deaths
Deaths of person in custody
Deaths occurring in institutions, aged
Deaths from violence
Suicides
Deaths occurring in a suspicious, unusual, or
unnatural manner
Crime Scene Investigation
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Police officers may seize anything relevant
to the investigation at the crime scene and
to maintain the security of the scene until
it is ordered released by the coroner
following the post mortem examination
Processing the Crime Scene
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Focus of police investigation is the
collection of physical evidence
CSI (“Crime Scene Investigation”) carried
out by a mobile crime lab
Police prepare a description of what they
find
Police photograph a scene
Police prepare diagrams of sketches
Police collect evidence
Crime Scene Procedure
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Important to safeguard the continuity of
evidence:
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No exhibit is left unattended from the time of
its seizure until it is deposited in the police
property – stage facility
The officer who seized the item, or the case
officer, must secure the evidence in the police
property locker, which is under the control of
the property clerk
Crime Scene Procedure
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The transfer of any evidence to the forensic
laboratory is the responsibility of the case officer
and/or his or her designate
The transfer of evidence to and from court is the
responsibility of the case officer
No exhibit can be removed from the control of
the property clerk without the appropriate
authority and signature
The case officer is the officer in charge of the
investigation
Processing Physical Evidence
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Forensic scientists job is to put the
evidence together correctly like the pieces
of a puzzle
Analysis of the evidence may involve
biology, chemistry, physics, anthropology,
geology, and computer science
Often called on to give expert testimony in
court
Humour Break
Some Pictures Made with
Fingerprints
Fingerprints
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Along with DNA, fingerprints are
considered by many to be the best way to
identify a suspect
Fingerprints never change and are unique
to each person
Fingerprint patterns can be identified as
one of three types:
Fingerprints
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1. Arches, forming ridges that run from
one side of the print to the other and
curve up the middle
2. Loops, showing stronger curves than
arches with ends that start on one side of
the finger, loop around, and end up in the
same place
3. Whorls, forming complete ovals, often
in a spiral pattern around a central point
Fingerprint Patterns
Latent Fingerprints
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Created when a person’s fingers come into
contact with an object such a piece of
glass or of plastic
Created by a residue of oil and
perspiration from the fingertip
Usually invisible and requires the
application of chemicals or laser light
Visible Impressions or Fingerprints
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Result of a finger’s contact where blood,
dust or grease has been previously
deposited
Fingerprints
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Moulded fingerprints:
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Leaves a visible impression in a soft
substance such as clay, wax or putty
Fingerprints Processing
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Fingerprints taken from crime scene are
sent to a central repository administered
by the RCMP in Ottawa
If the quality of the fingerprint is adequate
(20% of a print) and the individual’s prints
are on file as a result of previous arrest or
conviction the individual’s identity can be
determined through comparison
Fingerprints Processing
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Characteristics of each print are examined
by experts
When there are a sufficient number of
characteristics thought to be identical
(usually 10 to 12 points of comparison) an
expert may form the opinion that the print
submitted is that of the individual whose
prints are on file
Henry System of Fingerprint
Classification
Galton Details, Points of Identity or
Minutiae
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Identification by fingerprints relies on pattern
matching followed by the detection of certain
ridge characteristics, also so known as Galton
details, points of identity, or minutiae, and the
comparison of the relative positions of these
minutiae points with a reference print, usually
an inked impression of a suspect's print. There
are three basic ridge characteristics, the ridge
ending, the bifurcation and the dot (or island).
Source: shs.westport.k12.ct.us/…/handout
Galton Details, Points of Identity or
Minutiae
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Identification points consist of bifurcations,
ending ridges, dots, ridges and islands. A single
rolled fingerprint may have as many as 100 or
more identification points that can be used for
identification purposes. There is no exact size
requirement as the number of points found on a
fingerprint impression depend on the location of
the print. As an example the area immediately
surrounding a delta will probably contain more
points per square millimetre than the area near
the tip of the finger which tends to not have that
many points.
Galton Details, Points of Identity or
Minutiae
Galton Details, Points of Identity or
Minutiae
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Dot
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Island
Galton Details, Points of Identity or
Minutiae
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Birfurcation
Galton Details, Points of Identity or
Minutiae
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Ending ridge
Galton Details, Points of Identity or
Minutiae
Image 1
Image 2
Galton Details, Points of Identity or
Minutiae
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In image 1 we see part of a fully rolled
fingerprint. Notice that the edges are cut-off so
you can safely assume that this is not a fully
rolled impression. If you take a look at image 2
you can see that the centre portion of this
impression has been sectioned out and 10 points
of identification have been labelled. That was
not all the points found but simply the ones that
could be mapped easily without cluttering up the
image.
Primary Classification Activity
Fingerprint Activity
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You are all going to take your fingerprints
(I will give verbal instructions)
After we take them, we will use the Henry
System of Classification to get your
fingerprint “number”
We will also see if there are any identical
numbers in the class
Trace Elements
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Includes dirt, dust, fibres and residue
Origin of these materials may provide a
link between a suspect and a crime
Material at an arson scene may produce
trace elements of an accelerant used to
start or maintain a fire
Trace Elements
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Further examination may uncover the
specific chemical composition of the fluid,
thus linking it to a suspect who possesses
the same material
Transfer of trace elements such as hair
and fibres between the perpetrator and
the victim is common in crimes such as
homicides, aggravated assault and
kidnapping
Hair
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If the sample contains the root, shaft and
tip, it may reveal:
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a person’s racial background
the area of the body from which the hair
originated
the person’s blood type
Fibres
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Examination may determine their point of
origin or manufacturer
Matching the fibres found on the sole of
the shoe of a victim with the accuser’s
residences
Blood
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In impaired-driving offences, blood
evidence is paramount
Also relevant in cases where a suspect’s
mens rea is in issue as a result of
intoxicating substances
Blood is a fluid that conforms to the laws
governing the motion and properties of
other fluids
Blood
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Study the size and shape of blood drops
on a floor can indicate the height from
which they fell and thus the location of the
wound
Shape may indicate movement; a person
in motion while bleeding produces a tearshape drop, with the narrow end
indicating the direction of travel and the
rounded end pointing towards the bleeder
Blood
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Blood splatter patterns on the wall may
indicate the force and direction of a blow
and indicate how far the victim was from
the wall when the wound was inflicted
Gunshot Residue
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Includes:
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Gases
Unburned or partially burned power grains
Carbon particles
Trace of the bullet lubricant
Traces of primer components (lead, barium,
nitrates)
Fragments of soft bullets (lead antimony)
Fragments of the bullet jacket
Metal traces for the cartridge case or gun
barrel
Gunshot Residue
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These trace elements are deposited on the
hands of the person discharging the gun
Under circumstances, detectable and
identifiable
Gunshot Residue – Hand Wash
Test
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Requires the suspect to wash his or her
hands in a chemical solution
Solution is then sent to the laboratory for
analysis
Test can detect elevated levels of lead,
barium, and antimony
May indicate that the suspect has fired a
gun recently
Gunshot Residue
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GSR test cannot determine the time at
which the suspect may have fired the gun
It is less effective when the time between
firing the fun and taking the hand wash
exceeds four hours
Gunshot Residue – Scanning
Electron Microscopy SEM
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Provides results that appear to be more
accurate and consistent than the hand
wash test
Special utensil containing a gummed
substance is held against the skin and
them removed
GSR adheres to the gummed substance,
which is then prepared for examination by
the scanning electron microscope
DNA: Deoxyribonucleic Acid
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All human beings have a distinctive
genetic code within their 46 chromosomes
Identification of an individual through his
or her distinctive genetic code
DNA: Deoxyribonucleic Acid
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Minute samples of:
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Blood including a blood stain
Semen
Saliva
Vaginal secretions
Skin
Hair follicles
Can be used…
DNA: Deoxyribonucleic Acid
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Are sufficient to produce reliable results even
when the sample combines two or more
substances
This contamination does not affect the reliability
of the test
Properly analyzed, it can identify an individual
with a certainty exceeding one in several billion
Has also been used to rule out suspects, or to
overturn wrongful convictions
Humour Break