Transcript Forensic Science

Seminar:
Introduction to
Forensic Science
Definition and Scope
Freddie Arocho-Perez
Kaplan University
SC155: Introduction to Chemistry
What is Forensic Science?
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The application of science to those criminal and
civil laws that are enforced by police agencies
in a criminal justice system.
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Any application of science to law enforcement.
Includes geology, chemistry, physics, biology, etc.
Criminalistics – any of the services provided by
a crime laboratory.
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For all intents and purposes, the term is
interchangeable with forensic science.
Sir Arthur Conan Doyle
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Author of the Sherlock Holmes series.
Popularized forensic investigation through
his novels.
Used up-and-coming detective methods in
his stories, including fingerprinting, serology,
firearm identification, and questioned
documents.
Major Contributors to the Field
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Mathieu Orfila (1787-1853) – father of toxicology:
the science of dealing with poisons and their
effects.
Alphonse Bertillon (1853-1914) – developed
science of anthropometry – the taking of a series of
body measurements for means of personal
identification (later replaced by more reliable
fingerprinting).
Francis Galton (1822-1911) – first thorough study
of fingerprints and how to classify them; offered
statistical proof of their uniqueness.
Major Contributors to the Field
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Edmond Locard (1877-1966) –
created the first rudimentary crime
lab in Lyon, France (1910).
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Locard’s Exchange Principle –
when a criminal comes in contact with
an object or person, a cross-transfer
of evidence occurs.
"Every Contact Leaves a Trace"
Major Contributors to the Field
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Every criminal can be connected to his/her crime
scene by something as small as dust particles
carried to or from the scene.
First to request that suspects’ clothing be
examined in the lab.
His success led to the establishment of police
labs in Vienna, Berlin, Sweden, Finland, and
Holland.
FBI
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Under director J. Edgar Hoover, national lab
for forensic services established in 1932.
FBI lab is now the world’s largest, with 1
million examinations each year.
Introduction to Crime Scene
Investigation
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The purpose of crime scene investigation is
to help establish what happened (crime
scene reconstruction) and to identify the
responsible person.
Carefully documenting the conditions at a
crime scene and recognizing all relevant
physical evidence.
Introduction to Crime Scene
Investigation
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The ability to recognize and properly collect
physical evidence is oftentimes critical to
both solving and prosecuting violent crimes.
It is important to determine the full extent of a
crime scene.
The Crime Scene
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A place where a crime has taken place.
A starting point for a criminal investigation.
A crime scene is not merely the immediate
area where a body is located or where an
assailant concentrated his activities but can
also encompass a vehicle and
access/escape routes.
Crime Scene Vocabulary
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Crime Scene: Any physical location in which a crime has
occurred or is suspected of having occurred.
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Primary Crime Scene: The original location of a crime or
accident.
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Secondary Crime Scene: An alternate location, such as where
additional evidence may be found.
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Suspect: Person thought to be capable of committing a crime.
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Accomplice: Second person associated with committing a
crime.
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Alibi: Statement of where a suspect was at the time of a crime.
Types of Evidence
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Evidence used to resolve a crime can be split into 2 areas:
testimonial evidence and physical evidence.
– The testimonial evidence would be any witnessed
accounts of an incident or crime.
– The physical evidence would refer to any material items
that would be present on the crime scene or the victims.
These items would be presented in a crime investigation to
prove or disprove the facts of the issue.
 Examples include DNA, the body itself, the weapon
used, pieces of carpet, blood and other body fluids,
fingerprints, or casts of footprints or tire prints.
 Trace evidence refers evidence that is found at a crime
scene in small but measurable amounts.
Crime Scene Search Patterns
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The purpose of a search is to locate,
identify, and collect any tangible
material which may be associated
with a suspect and/or victim from the
crime scene and/or the crime.
There are standard search patterns
used at a crime scene, especially
when the scene is very large. These
patterns include: spiral, grid, strip or
line, and quadrant or zone search.
Forensic Science disciplines at the
Illinois State Police Crime Labs
Investigating the Evidence
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Drug Chemistry - Determines the presence of
controlled substances and the identification of
marijuana
Trace Chemistry - Identification and comparison of
materials from fires, explosions, paints, and glass.
Microscopy - Identification and comparison of hairs,
fibers, woods, soils, building materials, insulation
and a broad group of materials referred to as
"particulate unknowns.”
Biology/DNA - Presence and comparison of body
fluids and dried stains such as blood, semen, and
saliva.
Toxicology - Determines the presence of drugs and
poisons in tissue, blood, urine and other body fluids.
Forensic Science disciplines at the
Illinois State Police Crime Labs
Investigating the Evidence
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Latent Prints - Identification and comparison of
hidden impressions from sources like fingers, palms,
feet, shoes, ears, lips or the tread on vehicle tires.
Firearms & Toolmarks - Examination and
comparison of fired bullets, discharged cartridges,
guns, gunpowder patterns, and marks left by erased
serial numbers in metal or by burglary tools like a pry
bar or screwdriver.
Questioned Documents - Side by side comparisons
of questioned handwriting and hand printing, ink,
paper, writing instruments, printers, photocopiers,
additions, eradications, obliterations, watermarks,
and impressions.
Analytical Instrumentation: HPLC
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HPLC: High-Performance
Liquid Chromatography
System is fully automated
using data acquisition
software.
HPLC is a commonly used
technique for separating
and analyzing sample
components in the forensic
laboratory.
HPLC Configuration
Analytical Instrumentation: HPLC
Evidence Examples
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Blood
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There are 150 known proteins, 250 known enzymes, and
many more antigens in blood.
Investigators can often estimate the time a crime occurred
from how dry the blood is.
The shape of blood at the scene (pool, drops, stains, or
splashes) can provides clues as to what happened as well as
the location and description of bloodstains.
Blood evidence is frequently used to eliminate a pool of
suspects.
Evidence Examples
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Wounds
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Wounds can often be matched to weapons, tool marks on
the weapon, or at least the weapon's size, shape, and
length.
Wound pattern analysis is a special technique that often
provides clues to how a crime was committed or
characteristics of the suspect (left-handed, right-handed,
height, etc.).
Tool Marks
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When a tool is made and used, tiny nicks and chips begin to
form, which adds unique characteristics to its blade and
edges. Tools may also pick up traces of substances it came
in contact with.
Evidence Examples
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Skeletal Remains
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Forensic anthropologists analyze skeletal remains to
determine four characteristics for a victim: age, sex, race,
and stature.
Determining the sex of a victim is the first step in the
analysis of unidentified human remains. The innominate
bone, which comprises the pelvis, offers the most
definitive traits. The humerus or femur is also used and an
analysis of the skull can give investigators clues about the
whether the person was male or female.
Determining the age and stature (height) of a victim can
be done by analyzing the development of the teeth, bone
growth, and the length of specific bones, such as the
femur.
Determining the race of a victim can be done by analyzing
the skull for specific characteristics that are common
among people of different races.
Evidence Examples
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Fingerprints
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A fingerprint can conclusively identify both suspects and victims,
since everyone has unique fingerprint patterns.
Databases, such as AFIS (Automated Fingerprint Identification
System) are available for rapid computerized searching, on
national, state and local levels.
Bite Marks
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Each of the thirty-two teeth in humans is unique due to age and
wear.
Bites can tell how quickly the offender subdued the victim and
can often be matched to dental records.
Evidence Examples
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Facial Composites
– Investigators work with sketch
artists and eyewitnesses to
create facial composites, or
sketches of a person’s face.
– Today many police
departments are using facial
reconstruction software to help
them with this task.
– The composite may be used
internally to assist officers in
identifying the suspect or used
externally through local media
(radio, TV, and newspaper) to
solicit leads from citizens.
Evidence Examples
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Fluids
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Semen, saliva or sweat can usually be found in spatters,
drops or stains and can be fresh, coagulated or in dried
form.
Each form has its own particular method of collection and
preservation.
Bodily fluids, such as vomit, can be found at scenes and
used to test for alcohol, drugs, and poisons. Cigarette butts
may contain dried saliva. Semen containing sperm is
particularly valuable for DNA analysis.
Evidence Examples
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Paint
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Paint is examined with microscopes and several
analytic instruments to determine its chemical
composition. There are forty thousand different
types of paint classified in a database available to
police.
Paint can be transferred from one vehicle to
another in an accident or a paint chip left at the
crime scene can be used to determine the make
and model of the vehicle it came from. Most paint
evidence submitted to a lab will come from hitand-run cases involving automobiles.
Evidence Examples
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Explosives
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Powders and exploded/unexploded devices can
be examined to determine what type of explosive
may have been used.
After the Bomb Squad makes sure a device is
safe, they submit a sample of the explosive or the
debris to the Trace Unit. These items are then
analyzed with chemical spot tests and analytical
instrumentation to determine their chemical makeup to help identify which type of explosive was
used.
Evidence Examples
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Glass
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In car accidents, fragments of glass can be
embedded in a victims’ hair or clothing. In break
and entries, suspects often get glass fragments
on their clothing.
Glass particles can be compared to particles
collected from the crime scene to determine if
they have a common origin.
Glass tint, thickness, UV fluorescence, density,
and refractive index can all be used to match
glass samples to glass found at a crime scene.
Evidence Examples
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Dust & Dirt
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This type of evidence can reveal where a person has been,
where they live, where they work, and if they have pets.
Alibi soil samples are taken in many criminal investigations
with most soil samples taken from the top surface of the soil
in small amounts.
Firearms (Ballistics)
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Characteristics of ammunition, components and residue are
examined to find matches.
Bullets are never removed from their holes. The whole
surrounding surface is cut out.
Crime Scene Protocol
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Interview - The 1st step in processing a crime scene begins
with interview of the first officer at the scene or the victim to
determine what allegedly happened, what crime took place,
and how was the crime committed. This information may not
be factual information but it will give the investigators a place
to start.
Examine - The 2nd step in the investigating a crime scene,
which will help identify possible items of evidentiary nature,
identify point of entry and point of exit, and getting the
general layout of the crime scene.
Photograph - The 3rd step in the protocol, which involves
creating a pictorial record of the scene and record items of
possible evidence. Crime scene photographs are generally
taken in two categories, overall views and items of evidence.
Crime Scene Protocol
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Sketch - The 4th step in the protocol involves drawing a
rough sketch to demonstrate the layout of the crime
scene or to identify the exact position of the deceased
victim or evidence within the crime scene. A crime
scene sketch may not be completed on every case,
however some form of sketching usually occurs in most
cases, i.e., on a fingerprint lift card to identify exactly
where the latent was recovered.
Process – This is the last step in the protocol. The
crime scene technician will process the crime scene for
evidence, both physical and testimonial evidence. It is
the crime scene technicians responsibility to identify,
evaluate and collect physical evidence from the crime
scene for further analysis by a crime laboratory.
Processing the Crime Scene
There are 7 steps to processing a crime scene:
1.
Secure and Isolate the Crime Scene
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Record the Scene Photograph, Sketch, Take Notes
3.
Conduct a Systematic Search For Evidence
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Collect and Package Evidence
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Maintain Chain of Custody
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Obtain Controls
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Submit Evidence to the Laboratory
Crime Scene Investigation Team
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Team Leader
Photographer and Photographic Log
Recorder
Sketch Preparer
Evidence Recorder/Evidence Recovery
Personnel
Specialists
Crime Scene Search Patterns
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Important things to do during
a search:
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Search from the general to
the specific for evidence.
Be alert for all evidence.
Search entrances and exits.
Discuss the search with all
personnel.
Recording the Crime Scene
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Documentation includes transient details
such as lighting (on/off), drapes
(open/closed), weather, or furniture moved
by medical teams.
The scope extends to possible arguments
which might be made in this case
(suicide/self defense) and documenting
conditions supporting or refuting these
arguments.
Recording the Crime Scene
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Important to
recognize what
should be present
at a scene but is not
(victim's vehicle or
wallet) and objects
which appear to be
out of place (ski
mask) and might
have been left by
the assailant.
Photographing the Crime Scene
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Photograph entire area before it is
entered.
Photograph victims, crowd, and
vehicles.
Photograph entire scene with
overall, medium and close-up
coverage, using measurement
scale when appropriate.
Photograph major evidence items
before they are moved.
Photograph all latent fingerprints
and other impression evidence
before lifting and casting are
accomplished.
Prepare photographic log and
sketch.
Sketching the Crime Scene
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Documentation of physical evidence locations, as well
as measurements showing pertinent size and distance
relationships in the crime scene area.
Collecting Physical Evidence
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Any collected evidence
should have its location and
condition documented
before it is removed.
Describe evidence and its
location on appropriate bag
or envelope.
Evidence should be
collected in appropriate
containers, wearing gloves.
Collecting Physical Evidence
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Containers/envelopes should
be sealed with tamper-proof
tape.
Seals should be signed.
Chain of Custody must be
maintained:
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Sign/date evidence container.
Maintain evidence log.
Obtaining Controls from the Crime
Scene
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Controls are physical
evidence whose origins
are known, such as
carpet fibers from a
suspects home, that
can be compared to
crime scene evidence.
The crime lab must
have a thorough
sample of control
materials for
comparison.
Submitting Evidence to the Crime Lab
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Evidence can be submitted
to the crime laboratory by a
crime scene investigator
personally or via the mail
Chain of Custody must be
maintained at all times
Many labs require specific
documentation before they
will process evidence
Evidence evaluated by the
lab may take a long time to
process, or be held due to
back log.
Identification of Illicit Drugs
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Drug evidence can be collected in the form of:
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Powders
Tablets
Capsules
Vegetable matter
Liquids
Pipes
Cigarettes
Cookers
Syringes
They contain active drug ingredients as well as inactive
substances or additives (sugar, starch, quinine) to increase
quantity, dilute potency, and raise total value.
Classes of Drugs
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Narcotics:
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analgesics, relieve pain by depressing central
nervous system activity;
leads to physical dependence;
opium derivatives, such as morphine, heroin
Hallucinogens:
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Cause marked changes in thought processes,
perceptions, and mood
Includes marijuana, LSD, PCP, MDMA
Classes of Drugs
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Depressants:
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Alcohol, barbiturates, tranquilizers, inhalants
Stimulants:
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Amphetamines, cocaine, crack
2-Step Procedure:
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1) Use screening tests to reduce the number
of possibilities to a small and manageable
number.
2) Use more sophisticated tests to pinpoint
and confirm the identity of the drug.
Illicit Drugs – Color Tests
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Color tests: not conclusive evidence – presumptive
test only.
Marquis test: 2% formaldehyde in sulfuric acid –
turns purple in the presence of heroin, morphine,
and other opium derivatives.
Duquenois-Levine test:
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Solution A – 2% vanillin and 1% acetylaldehyde in ethyl
alcohol
Solution B – concentrated HCl
Solution C – chloroform
Purple color in the chloroform layer indicates marijuana
Illicit Drugs – Color Tests
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Van Urk test:
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1%p-dimethylaminobenzaldehyde in 10% conc. HCl and
ethyl alcohol
Turns blue-purple in presence of LSD
Difficult to perform in the field because of small batches of
LSD produced
Scott test:
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Solution A – 2% cobalt thiocyanate in 1:1 water and
glycerine
Solution B – conc. HCl
Solution C – chloroform
Test for cocaine
Sophisticated Tests for Drugs
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Microcrystalline tests:
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Chemical reagent is added to drug sample on a
microscope slide
A chemical reaction happens, forming a
crystalline precipitate on the slide
The sizes and shapes of the crystals are specific
to a particular type of drug.
Sophisticated Tests for Drugs
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Chromatography:
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Thin-layer and gas chromatography separate
drugs from their diluents
Requires a comparison between known and
unknown drugs, so one must have a tentative ID
before using.
Complements the color and crystal tests.
Sophisticated Tests for Drugs
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Spectrophotometry:
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Measures the absorption of light in the ultraviolet
(UV) and infrared (IR) regions of the
electromagnetic spectrum.
UV is not conclusive; establishes probable identity
only
IR can specifically identify a substance, like a
fingerprint
Sophisticated Tests for Drugs
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Mass spectrometry:
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Sample is exposed to high-energy electrons to
break the sample molecules – no two compounds
fragment in exactly the same way
Used in conjunction with gas chromatography
(GC/MS)