FORENSIC SCIENCE

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FORENSIC SCIENCE
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Locard Exchange Principle
It was the French scientist Edmond Locard, a
pioneer in forensic science, who declared (in
French) that "it is impossible for a criminal to
act, especially considering the intensity of a
crime, without leaving traces of his presence."
"Every contact leaves a trace."
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Four Main Elements to an Investigation
First, the crime scene is thoroughly documented.
Photographs, videos, sketches and notes
describing the scene are made.
Second, the physical evidence is collected and
unknown substances are sent to the laboratory for
identification and analysis.
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Four Main Elements to an Investigation
Third, the results of the laboratory analysis of
the physical evidence are compared to witness
statements.
Finally, both witness statements and laboratory
results are used to disprove the investigator's
hypotheses until one remains.
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Bertillon in 1883
Anthropometrics
literally meaning "measurement of humans"),
refers to the measurement of living human
individuals for the purposes of understanding
human physical variation.
From these studies, it was discovered that ratios
existed between various body parts and the height
of the person.
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Ballistics the study of the motion of bullets
and their examination for distinctive
characteristics after being fired. Examiners can
use this evidence to match bullets or bullet
fragments to specific weapons.
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Blood Typing
Karl Landsteiner in 1901
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Large spots - the blood was travelling at a
relatively low velocity
Small spots - the blood was travelling at a
relatively high velocity. (More force equals
smaller splatter)
Elongated drops - victim was moving, their speed
relative to the amount the spots are stretched
and how far they are spaced apart. (Also
indicates directionality)
Void in otherwise uniform splatter - something
blocked the blood spray.
Contact - large stain on a surface caused by
contact with a bloody object.
Cast-off - straight, elongated lines of splatter
indicating that blood was thrown by a moving
object in a change of direction. (Can show how
many times a victim was struck)
video
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DNA
This provides a powerful technique for uniquely
identifying the person or animal who left traces
of body fluids at a crime scene. Indeed, this is
the best method presently known for such
identification.
DNA Electrophoresis the process that separates
DNA using gel and electricity
DNA Profiling the process of testing to identify
DNA patterns or types
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TOXICOLOGY
Toxicology the study of poisons and drugs and
their effect on human and animal populations.
Gas Chromatograph (GC) a forensic tool used to
identify the chemical makeup of substances used
in the commission of crimes. The questioned
substance is burned at high temperatures. The
temperature at which this material becomes gas is
then charted to determine its makeup.
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Forensic Odontology
Bite mark comparison is fairly new, however,
going back to the mid-1970s.
Criminals seem to leave their bite impressions on
food products, chewing gum, or more commonly on
the skin of their victims
There are seven (7) types of bite marks
1. hemorrhage -- small bleeding spot
2. abrasion -- undamaging mark on skin
3. contusion -- ruptured blood vessel, bruise
4. laceration -- punctured or torn skin
5. incision -- neat puncture of skin
6. avulsion -- removal of skin
7. artifact -- bitten-off piece of body
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Fingerprints

• Sir Francis Galton in 1888,published his book,
  "Fingerprints", establishing the individuality
  and permanence of fingerprints. The book included
  the first classification system for fingerprints.

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Solve the crime