Wednesday 5/29/13
• AIM: how can we be successful on our
post assessment exam?
• DO NOW: Grab a text book and define
criminalistics and evidence.
• Explain the difference between class and
individual characteristics
• HOMEWORK: Review sheet
• a shoe print is left at a burglary scene.
Identify each of the following as individual
or class characteristics.
– Manufacturer of shoe
– Pattern of print
– Sole imprint
– Size of shoe
Criminalitics
• the application of science to the
physical evidence
•
bloodstains
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DNA
•
bullet trajectories
– includes the psychological angle
– studying crime scenes for motives, traits,
and behavior.
Evidence:establishes or disproves
a fact
– Testimonial Evidence
– Any witness accounts of the crime
– Physical
– any material items that would be present on
the crime scene
– Hard evidence left at the crime scene
– Fingerprints, blood or semen samples, hair
samples etc.
Individual vs Class
• Individual evidence: can be connected to
one single person
– DNA, fingerprints, hair if there is a follicle,
glass, bite marks
• Class evidence: related to an entire group
– Glass, hair, blood
Locard’s Exchange
Principle –
• It was Locard’s belief that when
a criminal came in contact with an
object or person, a crosstransfer of evidence occurred.
• The exchange of materials between
two objects that occurs whenever two
objects come into contact with one
another.
Crime Labs
– 1915: Edmond Locard
– Lyon France
– His only instruments were a microscope and
spectrometer
– 1923: Los Angeles Police Department
– First Crime lab in the US
– Current Day FBI has the LARGEST crime lab
in the WORLD
United States crime labs
• Currently there are 320 in the US alone
– Operate on different levels
– Federal
– State
– County
– Municipal
– Crime Labs may function as part of the police
department or the District Attorney’s office
– Medical examiner or coroner
Criminalist or Forensic analyst
• JOB is to analyze evidence and testify about the
facts
– Provide an expert opinion
– NO BIAS NO OPINIONS
• 1960’s supreme court began depending on
scientific evidence
• 1990’s DNA profiling was discovered
– Creation of a National DNA profile system
• Today FBI has the largest forensics lab in the
world
Legal terms to know
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Stare decisis
Corpus delecti
Nolo contendere
Pro bono
• Corpus delicti: the principle that a crime must have
been proven to have occurred before a person can be
convicted of committing that crime.
•
Stare decisis: "the decisions remains" or words to
that effect, It says that once a decision is made it
becomes a precedent and the courts have a bias toward
respecting and preserving that precedent. It is necessary
to ensure that the law be predictable and consistent and
not change every time a different judge or bench looks at
an issue
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Pro bono: work taken voluntarily.
•
Nolo contendere: refers to a pleas of no contest.
An alternative to pleading guilty or not guilty.
Crime Scene Analysis
• 1- Seal off the crime scene
• 2- each piece of evidence is packaged
separately
• 3-begin to mentally document the scene
• 4- check the body if there is one
• 5- isolate witnesses
• 6- observe the scene for evidence
Maintain a chain of custody
• A list of each person who comes in contact
with the evidence
• Makes sure evidence is not tampered with
in order to be admitted into court
• NO CHAIN OF CUSTODY NO COURT
ADMISSION
Branches of a crime unit
– Physical Science Unit
• Chemistry
• Drug test
– Biomolecular evidence
• Physics
– Trajectory
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Geology
Soil
Rocks
mineral
Basic services of a crime unit
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Biology
Firearms
Questioned document: checks, diacritics
Photography
Odontology
Latent fingerprint
Polygraph
diacritics
• marks such as an accent or a tilde that
indicate the correct pronunciation of a
letter or combination of letters which,
without the mark, would be pronunced
differently.
• Crossing of t dotting of i
Optional Services of a crime unit
– Toxicology unit
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Usually under the medical examiners direction
Drugs,alcohol, poisons
Fingerprint unit
Polygraph unit
Voiceprint analysis
Telephone threats or taped messages
Voiceprint: transforms speech into visual graphic
Evidence Collection unit
Cyber bullying
• Voiceprint Analysis Unit - The sound
spectrograph is an instrument that
transforms speech into a visual graphic
display called a voiceprint.
Forensic entomology
• Observes the development of bugs
Forensic Pathology • This field involves the investigation of
sudden, unnatural, unexplained, or
violent deaths,disease
• Rigor mortis
• Algor mortis
• Liver mortis
1- Algor Mortis: Time of death
• Check the body core
temperature
• At the scene, a
thermometer is
inserted into the liver
• Body temperature
drops about one
degree Celsius per
hour after death
1- Algor Mortis Time of death
continued
• Body Temperature cools until it reaches
room temperature
• Rate of cooling is determined by
– Location and size of body
– Victim’s clothing
– Weather conditions
– General rule; body looses 1-1.5 degrees
every hour
2- Stiffening of the body
• Rigor Mortis:
Muscles relax and
then become rigid
• Joints of body stiffen
and lock
– Sets in within 30
minutes to 3 hours
after death
– Goes away 24-36
hours after it begins
3- Liver Mortis
• Blood settles in parts of the body closest to
the floor
• Happens 6 hours after death
• More efficient in determining cause of death
Forensic anthropology
• Analyzes bones
– Age, sex, race, height NOT weight
• Sutures: determine age
Fingerprints
• Should be developed within 24 hours of
the crime, found on any surface NOT ON
A BODY
• 3 types of prints
• Visible, plastic, latent
Fingerprint patterns
Loops
whorls arches
% in general
population 60 - 65
30 - 35
5
Visualizing a human fingerprint
• MOST REACT with sweat oils
• Development is based on the surface it is found
on
• Cyanoacrylate ester: found in super glue
• Can visualize a print on a porous surface
• Ninhydrin: white powder or clear liquid
– Reacts with the amino acid in skin
– Turns purple when amino acid is present
• Iodine: drawback is when the vapors disappear
the print disappears
Hairs and fibers
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Human hair characteristics
Cuticle
Cortex
Medulla: 1/3 of the hair shaft diameter
other animals about 1/2
• ACT: anagen, catagen, telogen
Fiber patterns
• Wayne Williams
Natural fibers are derived in whole from
animal & plant sources
Coton, wool
REGENERATED FIBERS use
CELLULOSE from plant materials
mixed with a solvent to produce a fiber
rayon, acetate, triacetate
Drugs
• Analgesics: relieve pain
• Spot tests
• Blood alcohol content: alcohol is dissolved
in the blood and leaves the body
unchanged in breath, sweat and urine
COLOR TESTS: for screening only
A drug is
mixed with a
reagent
which turns
colors.
Bullet caliber
• Caliber is a measurement of the diameter
of the gun
Human blood
• Class characteristic
• Determined by the antigen present
– 3 alleles but only 2 antigens
• Blood type A has antigen A
• To determine if a sample is human,
precipitin tests are used
– Basically antigen antibody response
Fire: parts of a fire
• Fuel + oxygen= carbon dioxide, water,
heat and flame
Terms to know
• CODIS: Combines DNA Index System
• AFIS: Automated Fingerprint Identification
system
• IBIS: Integrated Ballistics
• IAFIS: Integrated Automated Fingerprint
Chromatography
• Capillary action
• Retention time
• Rf value
UNKNOWN SAMPLES
KNOWN SAMPLES
KNOWN
HEROIN
Rf - a value
KNOWN
QUININE
given to the
distance
traveled by each
compound.
Somewhat
unique to the
compound.
Comparison Microscope
• Used to compare unknown samples to
known samples
• Places samples side by side