Download forensic investigation - Understanding Canadian Law

FORENSIC INVESTIGATION
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 Click on Interactive Game
Place of Entry
Clue #1
What is the difference between a two dimensional and three dimensional
impression of footwear?
Footwear impressions are taken by the Forensic Identification Unit. They photograph them
individually and in a series, with and without a ruler. The photographs are taken from all sides to
show as much detail as possible. Castings are also made.
Footwear, as it is worn down, acquires individuality. Defects such as cuts and abrasions occur.
This individuality shows up when a footwear impression is left at the scene of a crime. Two types
of impressions can be left behind: two-dimensional, and three-dimensional. A two-dimensional
impression is one where footwear transfers an image to a surface or an object after it has come in
contact with a surface that is coated. The footwear then removes some of the coating. A threedimensional impression is one where footwear presses into something soft that retains the
impression of the footwear.
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Clue #2
Explain the different types of striations that can be made by tools.
Evidence of tool marks are collected by the Forensic Identification Unit. Tool marks and the area
containing the marks are carefully photographed and sketched, especially when the whole object
or area cannot be submitted to the lab. At the lab, they identify specific tools by comparing tools
and marked objects.
Impressions (striations) left by tools are their 'fingerprints'. There are three types of tool mark
impressions: 'compression', where a tool surface presses into a softer material; 'sliding', where a
tool scrapes across a surface causing parallel striations; 'cutting', when there is a combination of
compressing and sliding.
Clue #3
How are paint chips gathered?
Where might minute traces of paint be found?
Paint chips found at a crime scene are collected by the Forensic Identification Unit. They are
collected by holding a paper bindle open and scraping chips into it with a clean knife type blade.
The paint chips are then analyzed at a forensics lab by a technician.
Paint chips are often found when a tool is used on a painted surface. Minute traces of the paint,
when the tool is found, can be matched to the crime scene. Minute traces may also be found on a
suspect's clothes or person. The matching is done using the concepts of class and individual
characteristics. This methodology also applies with incidents involving motor vehicles.
Clue #4
When creating a composite drawing, how does the computer database help the
artist?
What characteristics will the artist note when completing the composite?
When there is a witness to a possible suspect, the Forensic Identification Unit gets as much detail
as possible from the witness. A forensic artist will then do a composite drawing of the possible
suspect's face manually, or use a computer for the image. Sometimes both methods are used.
When computer imagery is used, a database of many styles of facial features is available to
them. Showing them to a witness enables the witness to come up with a clear image. The artist
also notes height, weight, hair colour, eye colour, gender, race, and age of the suspect. The
artist's success comes from listening very carefully to the witness. With a composite drawing, the
Police have a much better chance of finding a suspect.
Place of Struggle
Clue #1
- Click Envelop (Standing)
What can hair tell us about a person?
What is “junk” DNA? Why is it so helpful?
Hair strands found at the crime scene are picked up by the Forensic Identification Unit using their
fingers or tweezers. At the lab, they analyze them and manually compare them to a possible
suspect's when a suspect is found.
Hairs found at a crime scene can tell much about a person. They can tell what race the person is,
if the person has any drugs, poisons, or diseases in their system, and can ultimately be matched
to a suspect. These factors can be revealed because hair contains DNA, and DNA encodes
information that determines a person's genetic makeup. The reason hair can tell the forensic
specialist what race a person belongs to, for example, is because all people within a particular
race have a similar DNA code sequence, as everyone who has brown hair has a similar code
sequence for brown hair. The coding sequences, however, are separated by 'junk' DNA. This
'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences are
random and unique to each person. This is why hair can identify its owner.
Clue #2
What falls under the umbrella of “Questioned Documents”?--Click papers on floor
Explain the difference between graphology and handwriting analysis.
Documents found at a crime scene are collected by the Forensic Identification Unit. They are
placed in cellophane or plastic envelopes, and are never marked, defaced, altered, or folded. At
the lab, they analyze the paper, ink, and handwriting.
Paper and inks, and handwriting analysis are forensic science disciplines under the umbrella
"Questioned Documents". Writing instruments, typewriting, photocopying, computer printers,
computer disks, forgery, gambling machinery, rubber stamps, and the dating of documents are
also disciplines under Questioned Documents. The concepts of class and individual
characteristics are applied to mechanically produced documents for the purposes of identifying
the equipment used. Handwriting analysis examines the design, shape, and structure of the
handwriting to determine authorship. Graphology is not a forensic science but rather, the study of
a person's handwriting to determine their personality traits.
Clue #3
What is AFIS?
-- Click fireplace
What is powder processing?
On what new materials can we now process prints from?
Fingerprints are gathered at the crime scene by the Forensic Identification Unit. Proper
precautions are taken not to damage or destroy fingerprints or add fingerprints to evidence. At the
lab, digital technology is used, called the Automated Fingerprint Identification System (AFIS).
Different surfaces require different techniques for developing fingerprints. The technique most
commonly known is powder processing. This is where powder is brushed over a print and minute
particles of powder cling to the print residue. The print is then lifted with a piece of tape. With the
advancement of forensic science, there are now special processes that develop prints on paper,
wood, cardboard, skin, and objects that have been in water.
Clue #4
What is “Locard’s Exchange Principle”? -- Click hand of person by chair
Fibres found at a crime scene are collected by the Forensic Identification Unit by their fingers or
tweezers. They are then placed in paper which is then sealed and marked. At the lab, they use
either a compound microscope or a comparison microscope.
Fibre analysis utilizes the concepts of class and individual characteristics, thereby determining
the type and colour of the fibre. In some cases, the expert can even determine the particular
garment or fabric. The search for fibres at a crime scene is done because of a principle called
"Locard's Exchange Principle": when someone comes in contact with another person or place,
something of that person is left behind, and something is taken away.
Place of Murder
Clue #1
What are cast off stains? What do they reveal? – Click Wall
Blood stain pattern information is gathered at the crime scene by the Forensic Identification Unit.
They take notes, sketch, photograph, and video tape the patterns. They are then examined by a
technician at a forensics laboratory.
Blood reacts, as all liquids do, in a predictable, consistent, reproducible manner. The types of
reactions are called 'standards'. These standards can tell the expert how a crime was committed
by the stain the blood leaves. Different splatters occur, for example, when blood falls from
different heights. When there is a blunt force trauma, and blood splatters, the stains left are called
'cast off stains'. These cast off stains reveal the direction and number of blows, the size of the
object used, the orientation of the person, and if they are right or left handed.
Clue #2
How are blood samples gathered? How are they transferred? – Click Hand
Blood samples at the crime scene are collected by the Forensic Identification Unit. They are
picked up by a gauze pad or other clean sterile cotton cloth, rolled in paper or placed in a brown
paper bag or box, which are then sealed and labelled. Plastic containers are not used. The blood
is then analyzed at a forensics lab by a technician.
Blood found at a crime scene can tell through chemical analysis if the person has any drugs or
poisons in his or her system. Through DNA analysis a person's genetic make up may be
identified. A very important use of DNA typing is the identification of perpetrators of a crime by
comparison of biological samples of suspects against biological specimens that the perpetrator of
a crime has directly left at the crime scene (e.g. semen, saliva, skin, or blood). The reason blood
can tell the forensic specialist what race a person belongs to, for example, is because all people
within a particular race have a similar DNA code sequence, as everyone who has brown hair has
a similar code sequence for brown hair. The coding sequences, however, are separated by 'junk'
DNA. This 'junk' DNA is non-coding and separates coding sequences. The 'junk' DNA sequences
are random and unique to each person. This is why blood samples can identify or eliminate a
suspect.
Clue #3
How are wounds analyzed? Give an example. – Click neck
Wounds on a victim are looked at by the Forensic Identification Unit and photographed. At the
lab, they are further analyzed by a forensic pathologist.
Wounds are analyzed using the concepts of class and individual characteristics. For example, an
incised wound is the cutting injury caused by the slicing action of a blade-like object. The edges
are smooth, but this could be from a serrated or smooth blade. A puncture made by a sharp
object would be a different class of wound.
Clue #4
What does a pathologist determine? – Click clock
What is the difference between livor mortis, algor mortis and rigor mortis?
The time of a victim's death at a crime scene is estimated by a forensic pathologist. Further
information about the victim is gathered when the autopsy is done at the lab. The pathologist
determines how and why the victim died, and whether it is a homicide, suicide, accidental death,
or death by natural causes. If it is a death by trauma, they look for a laceration, incised wound,
puncture, abrasion, contusion, or gunshot wound.
For the time of death, the pathologist considers algor mortis, the cooling of the body; livor
mortis, the setting of blood in the dependant regions following death; and rigor mortis, the
chemical reaction that causes rigidity in the muscle groups immediately following death. Livor
mortis can also determine whether or not the body has been moved.