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BIOL 3318 - Forensic Biology - Unit 1 Test

UTD - BIOL 3318 Spring 2011: Forensic Biology - Instructor: Anwu Zhou, PhD
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Forensic Science
The application of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system.
Services of a crime laboratory.
3 Major Categories of Forensics
Physical Forensics
Branch of science that deals with matter (anything that has mass, takes up space or energy, or involves the ability of a machine or other object to do work)
Crime scene technicians/investigators
collect many different types of evidence at a crime scene
Forensic engineers
reconstruct motor vehicle accidents, analyze mechanical systems (e.g. airbags), structural analysis
Ballistics experts
study firearms evidence
Latent fingerprint examiners
find, develop, and match fingerprints
Forensic imaging
digitally "age" photos of missing persons, suspects
Document examiners
study the authenticity of different types of documents (wills, ransom notes, money)
Chemical Forensics
Deals with chemical substances, drugs, or poisons found at crime scene or in a body, Unlikely to visit the crime scene
Forensic toxicologists
test body fluids/tissues/organs for the presence of alcohols/drugs/poisons (specialized form of chemist)
Arson/explosive specialist
determines origins of fires and mass disasters
Biological Forensics
Pertaining to anything that is, or once was, living, Unlikely to visit the crime scene
test for the presence of biological material, bodily fluid
DNA analysts
uses DNA to identify individuals, compares suspects to evidence
Medical examiners/coroners
(forensic pathologists): perform autopsies and identify cause of death
Trace evidence analyst
hair, fibers, paint
Forensic entomologists
study insects and their role in occupying the body after death
Forensic anthropologist
studies the origin of humans, skeletal reconstructions, lifestyle determination
Forensic odontologists
identify persons based on dental records, bite mark imprints
Computer/internet forensics
follows computer crime trail
Forensic accounting
financial fraud detection, auditing
personality profiling
Oldest forensic laboratory
LAPD in 1923
Formed by J. Edgar Hoover, 1932, Largest Forensic Lab in World
What's the need for Forensics Labs
Supreme Court requested police give greater emphasis to securing scientifically evaluated evidence
Lack of confessions/protecting criminals constitutional rights
Increase in crime rates
Advent of DNA profiling
FBI (Dept of Justice)
Federal Bureau of Investigation - broad investigative powers
DEA (Dept of Justice)
Drug Enforcement Administration - analysis of seized drugs
Bureau of Alcohol, Tobacco, and Firearms (Dept of Justice)
analyze alcohol, documents of tax law, examining weapons, explosives
US Postal Inspection Service
criminal investigations related to postal service
Basic Services of crime lab
Physical science unit (chemistry, physics, geology)
Biological science unit
Firearms unit
Document examination unit
Photography unit
Optional Services of crime lab
Toxicology unit
Latent fingerprint unit
Polygraph unit
Voiceprint analysis unit
CSI unit
The Frye standard (set in 1923)
The Frye v. United States decision set guidelines for determining the admissibility of scientific evidence into the courtroom.
The evidence in question must be "generally accepted" by the scientific community.
Frye Not Absolute
The Daubert Criteria (set in 1993)
Trial judges are ultimately responsible as "gatekeepers"
Expert Testimony
Presenting in a court of law findings and conclusions about a case
Must be qualified by a judge
May give opinion
Job is not to convict
Functions of a Forensic Scientist
Analysis of physical evidence
Expert Testimony
Training in the proper recognition, collection, and preservation of physical evidence
Basic CSI Procedure
Physical evidence recognition
Proper collection & packaging & preservation
Scene reconstruction
Types of Physical Evidence
Tool marks
Almost anything!
Info on the Corpus delicti
Latin meaning "body of evidence"—is the proof that a crime has taken place. When applied to a criminal case, proof of a crime must be shown in order to convict a person of the crime (fact finding)
Info on the Modus Operandi
Latin meaning "Method of operations"— criminals may repeat their behavior and/or techniques providing a signature
Linking persons, scenes, objects
linking suspect and victim is the most crucial information; Locard Exchange Principle at work
Locard Exchange Principle
States that whenever two objects
come into contact, a mutual
exchange of matter will take place
between them
The Integrated Automated Fingerprint Identification System
The Combined DNA Index System
The National Integrated Ballistics Information Network
The International Forensic Automotive Paint Data Query
Shoeprint image capture and retrieval
Primary crime scene
site of first criminal activity
Secondary crime scene
any subsequent crime scenes
Macroscopic crime scene
composed of many crime scenes
Microscopic crime scene
refers to the specific types of physical evidence found at macroscopic crime scenes
preliminary walk-through must be
done to note the following items
1. Mentally prepare a reconstruction theory
2. Any evidence that requires immediate protection or processing
3. Entry and exit points
4. Record initial observations of who, what, when, where, and how
5. Assess scene for need of additional personnel and agencies as required
Crime Scene Documentation
1. Notes taking
2. Videography
3. Photography
4. Sketching
What is biological evidence?
Seminal fluid
Tissue (muscle & organs)
Umbilical cord
Personal items: tooth brushes, hair combs, underware, eyeglasses, cigarette butts...
Most common biological evidence
Study of bodily fluids
Blood Components
Blood is composed of erythrocytes (red blood cells), leucocytes (white blood cells), thrombocytes (platelets), and plasma
We are interested in white blood cells (source of DNA)
White blood Cells
500,000 per drop, life span of 2-3 days
15-150 million per milliliter; heads are the source of DNA (contains a nucleus)
Blood Visual Examination
wet or dry, red to orange, brown to black
Semen Visual Examination
clear or yellow, dry and crusty
Chemiluminescent assays
Colorimetric Assays
Fluorescence assays
Presumptive testing
Providing a reasonable basis for belief or acceptance
Termed 'presumptive' due to possibility of false positives
Answers the question "Is it biological?"
Presumptive for blood, reacts with hemoglobin in RBC
Light is emitted as a product of the chemical reaction
Results in production of blue-white light
Photograph immediately
Works very well on odd stains
Reacts with metals and bleach (cause false positive)
Used mainly at the crime scene
Presumptive for blood, reacting with hemoglobin in presence of hydrogen peroxide
Color change to pink --- Colorimetric Assay
Result must be read immediately (60 seconds)
Reacts with potatoes and horseradish
Presumptive for blood, reacts with hemoglobin
Color change to blue-green after addition of hydrogen peroxide
Reacts with plant extracts, inorganic compounds
Presumptive for blood
Thin white strips with a chemical on tip that reacts with hemoglobin
Positive color change indicated by green or blue
Bleach may cause a false positive
Easy to use at crime scene
Presumptive for blood, reacts with hemoglobin
Must be exposed to a particular wavelength of light 425-485 nm from alternate light sources (ALS)
Emits yellowish-green color
Acid Phosphatase
Presumptive for seminal fluid
Can be detected in all males, vasectomized or not
Seminal fluid contains a higher level of AP than any other body fluid
Cauliflower produces false positive
Detection of Saliva
Not routinely performed
Amylase: enzyme present in saliva to aid in digestion; found in humans, animals, and plants
Detected by application of starch-iodine
Experimental Controls
Proper controls tell us that our experiments are working as expected and that we can trust the results
Positive Control
Tests the reagents/chemicals to ensure that they are working, produces a positive result in presence of a known sample
Negative Control
Tests the reagents/chemicals to ensure erroneous positives do not result
Controls for contamination
Challenges to biological samples
Environmental: temperature, humidity, cleanliness
Contamination: inadvertent addition of an individual's biological material /DNA
Mixtures: victim/suspect
Using the microscope to observe and analyze evidence not clearly seen with the naked eye (trace evidence)
something that comes from an animal source (mammals)
can be of plant origin, like cotton, linen, or made synthetically
Hair 3 anatomical regions
Stereo binocular microscope
Renders objects as 3D
Utilizes reflected light
2 eyepieces
Preliminary characteristics
are examined
Compound binocular microscope
Utilizes transmitted, bright light
Sample becomes transparent as light travels through it
Magnification up to 1200X the object's size
Morphological characteristics are examined
Comparison Microscope
Allows for simultaneous viewing of 2 samples
2 microscopes connected by an optical bridge
Can allow for superimposing images
Outside covering of the hair shaft
Formed by overlapping scales that always point toward the end of the hair
Scales are made of kerain
Provides two important features that make hair a good piece of physical evidence (attributed to the cuticle)
1. Resistance to chemical decomposition
2. Ability to retain structural features over a long period of time
The "meat" of the hair strand
Contains pigment granules
Examined using a 'wet mount'
Appears as a central canal running through the hair
Can be a dominant feature in animals
Not all hairs have a medulla, even within the same individual
Described as continuous, fragmented, or absent
Shape of medulla is important to distinguish between human and animal
Life Cycle of Hair
3 phases
Anagen = active growth
Catagen = transition
Telogen = resting
Growing stage
May last up to six years
85% of hair in anagen phase
Must forcibly pull hair to see anagen root, usually will have follicle around the root
Excellent source of DNA
Catagen Root
Transition phase
1% of hair in catagen phase
Telogen Root
Resting phase, ready to fall out
Loose 50 hairs per day
End is swollen like a cotton swab
14% of hair in telogen phase
No nuclear DNA
Natural hair color depends on the presence , amount, and distribution of melanin, a natural pigment found in the cortex
Melanin is housed inside granules which are scattered throughout the cortex with no set pattern or amount
Provides for hair color variation
Mixtures of these 2 create hair color via the type of melanin and size of granule
a black pigment
red/yellow pigment
Coronal or crown scales
resemble stacks of paper cups; found on rodents, bats
Spinous or petal
triangular; found on cats, seals, minks
Imbricate or flattened
overlap like roof shingles; found on humans and some animals
Caucasoid (European) Hair
fine to medium coarseness
straight or wavy
fine to medium sized granules
Granules evenly distributed
Negroid (African) Hair
Regularly curly or coiled
Larger pigment granules
High density of granules
Mongoloid (Asian) Hair
Coarse, straight
Wider in diameter than other groups
Medulla is continuous and wide
Can have a characteristic reddish color
Head hair
Most alterations (coloring, cuts, environmental insults)
Head hairs obtained years after a crime are generally not suitable for meaningful comparisons
Obtain 50 full length reference hairs from various sections of head
Pubic Hair
Not subject to as much variation
Obtain 25 reference hairs
Facial Hair
Beard and mustache hair are helpful
Limb Hairs (arm or leg)
Generally not meaningful
When conducting a hair comparison, look for the following
Body Area
Color and shape
Tips (broken, split, singed, cut)
Pigment density
Artificial treatment (dying, bleaching)
Nuclear DNA
found in nucleus of cell (only in hair roots)
can only be obtained from anagen hair roots
Must be pulled and have the follicle on them to be useful
Hair shaft can be used for mitochondrial DNA analysis
Especially important since it is most likely to find telogen hairs at crime scene
Mitochondiral DNA
found in mitochondria (hair shaft)
are organelles involved in energy production
They contain their own DNA
Maternally inherited
Coroner System
Originated in England around 1194
Had to be a Knight with a particular income
Appointed or elected
Judicial responsibilities
Investigated sudden deaths
English law is basis for US law
No provision for a coroner in US Constitution
Federal government had no death investigation operations (except DC) until 1990
Each state enacted coroner's law
Elected county official
Began to work in hospitals in 19th century using microscopes to examine tissue
Doctors became known as "pathologists":
Greek "pathos" = suffering or disease
"logos" = word or writing
Pathologists studies disease, its cause, and its diagnosis
Anatomic pathologists
autopsies, tissue examination; later utilized by police and ME
Clinical pathologists
body fluids
Medical Examiner
Educational requirements:
MD or DO degree
4 years post-grad training (residency)
Additional year of training in clinical and/or anatomic pathology in ME's office
Must pass a 2 or 3 day exam to be board certified
Forensic Pathologist's Role
Investigate the deaths of persons who die suddenly and unexpectantly or as a result of injury
Goals of Autopsy
Determine identity if possible
Determine cause of death (what directly led to the death?)
Determine manner of death (how the cause of death came to be)
Determine mechanism of death (biochemical or physiologic abnormality produced by the cause of death that is incompatible with life)
Rigor Mortis
A stiffening of the muscles that occurs following death
Due to the glycogen supply normally found in muscles being exhausted
Observed about 4 hours after death
Disappears during 24-36 hours after death when decomposition of muscle is occurring
Livor mortis
The discoloration of the body due to settling of red blood cells after blood stops circulating
Can be seen within an hour or so after death
Becomes fixed in about 12 hours after death
Disappears with decomposition after 36 hours
Determine the position of body when die
Algor mortis
The cooling of the body that occurs after death, assuming ambient temp is lower than body temp
A body exposed to 18-20°C (64-68°F) drops 1.5°C (2.7°F) per hour for the first 8 hours
Normal body temp is 37°C (98.6°F), thus if a body has been dead for 4 hours, temperature will be 31°C (87.8°F)
Natural Cause of Death
caused solely by disease, without trauma
Accidental Cause of Death
due to trauma occurring from acts lacking a high probability of producing harm or death
Homicidal Cause of Death
death from acts with high probability of producing bodily harm
Suicidal Cause of Death
only difference from homicidal manner is the person who acted
Asphyxial death (due to lack of oxygen to the brain) overlaps causes
Strangulation (mechanical)
Poisioning (chemical)
Electrocution (electrical)
Mechanical Trauma
1. Sharp
2. Blunt
A. Non-firearm
B. Firearm
Low Velocity
High Velocity
Sharp Force Injury
Injuries received from sharp objects: knives, swords, axes
Occurs when applied force exceeds tensile strength of tissue to which the force is applied
Produces incised wounds (not lacerations) with sharp edges
Death occurs by exsanguination: a major artery or heart must be damaged to cause death
Non-firearm Blunt Trauma
Caused by collisions and anything that can be used as a weapon other than a firearm
Usually requires a head injury to produce death
Mechanism of death is often blood that had been aspirated into lungs
Produces lacerations
Firearm Blunt Trauma
Firearm injuries are the most common homicidal and suicidal wounds seen in US - know
Injuries can be classified based on:
1, Propellants (gunpowder or smokeless gp/nitrocellulose)
2. Rifled versus smooth bored weapon (rifles or handguns; shotguns are smooth)
Injuries can be classified based on:
3. High and low velocity (higher the
velocity, extent of injury increases)
- Cut-off point is 300 m/s (328 yards)
4. Penetrating versus perforating
Penetrating wound has entrance wound, but NO exit wound
Perforating, both an entry and exit wound
Distance of barrel from deceased at time weapon was discharged:
Gases and smoke from unburned carbon are projected only a few inches
The gas produces contact or near-contact wounds, produces blackening of the skin and tears the skin
Chemical Trauma
Most common drug is alcohol but rarely kills directly
Legal limit is 0.08% (80mg/100mL)
0.25% (250mg/100mL) can cause coma
0.30% (300mg/100mL) slows breathing enough to cause death
Cocaine overdoses
CO: cuts off oxygen to brain, binds to hemoglobin in blood 300X stronger than oxygen
Blood levels of CO as low as 20% can be fatal (in fires, often reaches 90%)
Cyanide: acts similar to CO, distinctive odor like almonds, 50% of population cannot smell cyanide, can be killed by the gases released from cyanide in intestines
Thermal Trauma
Exposure to excessive heat or cold can produce death
Hypothermia: excessive cold
Hyperthermia: excessive heat
Difficult to diagnose
Thermal burns: localized wounds caused by hyperthermia
Above 150°F will produce burn upon contact for a few minutes
Wide range of circumstances cause burns: hot liquids, explosions, fire
Persons who die at scene of fire, usually die from inhalation of CO rather than the fire
Levels of CO in blood can be used to determine death: a 1-2% CO level is evidence person was dead before fire
Gasoline fires kills before person has a chance to inhale excess CO
excessive cold
excessive heat
Electrical Trauma
Low voltage (less than 1000 volts) interferes with beating heart, can produce burns
High voltage causes heart to continually sustain contraction (tetany) that when broken, will allow heart to have normal rhythm, produces burns less than a second