Forensic medicine
Dr.Eyad Abou Asali
Maxillofacial sur.
Ph.d
Definition and scope of Forensic Science
Forensic
science is application of science to the
law
Forensic science applies the knowledge &
technology of science for the definition &
enforcement of such laws
Forensic science is the application of science to
those criminal and civil laws that are enforced by
police agencies in a criminal justice system
History and development of Forensic
Science
Sir
Arthur Conan Doyle popularize crime
detection methods through his fictional character
Sherlock Holmes
Mathieu Orfilia and Alphonse Bertillion
Mathieu Orfila & Alphonse Bertillion
Father
of toxicology
Published first scientific treatise on the
detection of poisons & their effects on animals
& this established forensic toxicology as
legitimate scientific endeavor
Father of criminal identification
First scientific system of personal identification
Anthropometry used series of body
measurements to distinguish individuals
Francis Galton, Leon Lattes & Karl Landsteiner
Karl
Landsteiner
Francis Galton
Francis Galton, Karl Landsteiner
& Leon Lattes
First
definitive study of fingerprints & developed
a methodology for classifying for filing
Published book titled Finger Prints & explained
system for identification
Lansteiner discovered blood groups; A, B, AB, O
Lattes developed procedure determine blood
groups from dried bloodstain
Calvin Goddard, Albert S. Osborn & Walter C.
McCrone
Calvin Goddard, Albert S. Osborn & Walter C.
McCrone
Goddard
refined techniques for comparing
bullets fired using comparison microscope
Osborn developed fundamental principles of
document examination; authored Questioned
document book
McCrone pioneered use of microscope
Hans Gross, Edmund Locard
Hans
Gross
Edmund Locard
Hans Gross
Gross; First treatise describing application of
scientific disciplines and scientific method to
field of criminal investigation; produced a classic
book called Criminal Investigation- translated in
English
Edmund Locard
He
believed that when a criminal came in
contact with an object, a cross-transfer of
evidence occurred; Hence called Locard’s
exchange principle
He used a couple rooms and two assistants in an
attic to start the first police lab in Lyon France
USA
1932
first national crime lab developed in USA
with the FBI by J. Edgar Hoover for all law
enforcement agencies
World’s largest forensic laboratory & performs
over a million examinations every year
1981 FBI’s Forensic Science Research &
Training Center 1st time facility conduct
research to develop new & reliable scientific
methods applied to forensic science
Factors determining lab numbers increasing
The
demand for labs to perform drug analyses
single most important factor in expansion of
forensic services
Also the advent of DNA profiling has caused the
increase in labs & is the dominant factor in
explaining how general public perceives the
crime lab
Services of the Crime Laboratory
Reasons
for variations in services:
Variations
in local laws
Different capabilities & functions of organization to
which a laboratory is attached
Budgetary and staffing limitations
Often the sole purpose for crime lab creation has
been to process drug specimens
Basic services provided by full- service
crime labs
Physical
science unit: applies principles and
techniques of chemistry, physics & geology to
evidence evaluation; examinations of soil, drugs,
glass, paint, explosives etc are examined
Biology unit: applies principles and techniques to
identify DNA for profiling, stains & body fluids,
hair & fiber comparison, wood and plants
Basic crime lab
Firearms
unit: examination of firearms,
discharged bullets, cartridge cases, shot gun
shells, ammunitions, garments and other objects
examined to detect discharge of residues etc.
Document examination unit: handwriting and
typewriting on questioned documents studied;
analysis of paper & ink; erasures, obliterations,
document charred or burned
Basic crime lab
Photography:
examine and record evidence;
digital imaging, infrared, ultraviolet, and X-ray
photography techniques make invisible
information visible; court room presentations
Optional services provided by fullservice crime labs
Toxicology
unit: body fluids & organs examined
determine presence or absence of drugs &
poisons often this is shared with the medical
examiner’s or coroner’s office
Latent fingerprint unit: examination of latent
fingerprints submitted with other lab
examinations
Optional services provided by fullservice crime labs
Polygraph
unit: polygraph or lie detector used
primarily as a tool of the criminal investigator
Voiceprint analysis unit: cases involving
telephone threats, tape-recorded messages may
use unit to identify persons
Sound
patterns are suppose to be unique to the
person & and are captured on a voiceprint
Optional services provided by fullservice crime labs
Evidence-collector
unit: special trained personnel
collect & preserve physical evidence collected at
the crime scene
Functions of the Forensic Scientists
Analysis
of physical evidence: persons skilled in
applying principles & techniques of physical &
natural sciences to analysis of evidence but also
aware of the demands & constraints of court
system
Frye vs. United States: what ever conclusions
were deduced when examining evidence that
method has sufficient established acceptance in
particular field in which it belongs
Analysis of physical evidence
Books
and papers as well as a list of experts who
have used a method presented to a court is used
to fit the criteria of “generally accepted” by the
scientific community
Alternative to Frye standard is Federal rules of
evidence: part of it deals with expert testimony,
admissibility of all evidence
Analysis of physical evidence
continued
1993
the case of Daubert vs. Merrell Dow
Pharmaceutical, Inc. the U.S. Supreme Court
ruled that Frye standard or “general acceptance”
isn’t the prerequisite to admissibility of scientific
evidence; some state courts may apply this ruling
and use the Federal rules of evidence; trial judges
are the gate keepers to determine the
admissibility of scientific evidence; good case for
this ruling: Coppolino vs. State
Provision of Expert Testimony
Person
convinces a trial judge he/she has
possesses a skill or knowledge in a trade or
profession aid court in determining truth of
matters at issue considered expert witness;
knowledge obtained by experience, training,
education or combination qualification expert
witness; opposing attorney allowed cross
examine witness to maybe poke holes testimony
Expert witness examples
Training Proper Recognition,
collection & preserving evidence
Specially
training personnel to recognize, collect
and preserve physical evidence is highly valued
since without them, evidence could be useless
Police officers or detectives are often trained by
forensic scientists to know what to look for
Other forensic science services
Forensic
pathology: involves investigation of
sudden, unnatural, unexplained, or violet deaths;
medical examiners or coroners & answer
questions like who is the victim, what injuries are
present, when did the injuries occur, why and
how were the injuries produced. Primary roll is
to determine cause of death & by autopsy
Forensic pathology
A
medical examiner maybe able to determine
time of death by evaluating stage of death of
victim; immediately after death rigor mortis sets
in, appears 1st 24 hrs & disappears after 36 hrs;
livor mortis also sets in and blue to black color
appears on body closed to ground; can be used
to determine if body moved after death; algor
mortis sets in as body loses heat to the ambient
room temperature
Forensic pathology
Time
of death also determined by examining
potassium levels in ocular fluid
The rate at which potassium is released into the
vitreous humor maybe used
Also examining stomach can help note what the
victims last meal was
Forensic Anthropology
Concerned
with the identification and
examination of human skeletal remains
Examination of skeletal remains reveal their
origin, sex, approximate age, race, skeletal injury
Used to identify victims of mass disasters
Forensic Entomology
Study
of insects and their relationship to criminal
investigation
Used to estimate the time of death when it
circumstances surrounding crime unknown
Blow flies first arrive when body starts to
decompose; eggs are laid, and maggots or fly
larvae
Larvae consume tissue & organs
Forensic Entomology
Identification
of specific insects present in body
and approximate how long body left exposed by
examining the stage development of fly larvae;
weather conditions and geography affects results
Forensic entomology continued
Forensic psychiatry
Relationship
between human behavior and legal
proceedings examined;
Civil cases – determine people competent to
make decisions about wills, settling property or
refusing medical treatment
Criminal cases- evaluate behavioral disorders and
determine if people are competent to stand trial;
also behavioral patterns of criminals determine
profile
Forensic Odontology
Identification
of victims body is left
unrecognizable state
Teeth enamel, hardest substance in body
Use dental records such as x-rays, dental casts or
photograph of person’s mouth comparison made
between dental remains & suspect victim
Use bite marks in some cases like assault
Forensic engineering
Failure
analysis, accident reconstruction and
causes and origins of fires or explosions; auto,
plane and others involved
Questions asked
How
did an accident or structural failure occur?
Were the parties involved responsible
If so, how were they responsible
Lecture: Forensic Evidence
Physical Evidence
Any material either in gross or trace
quantities that can establish through
scientific examination and analysis
that a crime has been committed.
Forensic laboratories
Items of physical evidence
identification
evaluation
individualization
Classification of Physical Evidence
Trace evidence
extremely small items
stands on its own to prove an
alleged fact
Direct evidence
Prima facie evidence
evidence established by law
Circumstantial evidence
incriminates a person
Exculpatory evidence
helps to prove that an accused
individual is not guilty
Physical evidence utilization in other areas
of forensic investigation
Provides investigative leads for a case
Ties one crime to a similar crime or connects one
suspect with another
Corroborates statements from witnesses to or
victims of a crime
The elements of a crime help to determine what
will be useful as evidence.
Besides knowing what types of evidence to search
for, it is necessary to know where evidence is most
likely to be found.
Characteristics of evidence
Class characteristics
features that place the item
into a specific category
Individual characteristics
features that distinguish one
item from another of the same
type
E x a m in a t io n a n d a n a l y s is o f p h y s ic a l
e v id e n c e
H ig h e s t d e g r e e o f s c ie n t ific c e r ta in t y p o s s ib le w ith
c u r r e n t te c h n o lo g y
p h y s ic a l
id e n tific a tio n
c h e m ic a l
id e n tific a tio n
b io lo g ic a l
id e n tific a tio n
diffuse reflectance
spectroscopy
Fibers
Composition
FT-IR
microscopy
Physical properties Solubility,
melting point
Glass
Refractive index
Microscopy
Magnesium
Atomic
absorption
spectrophotometry
Shoes
Miscellaneous
Solidphase extraction; LC
Powder
Drugs of abuse
FTIR
Evidence
Techniques
Gunshot residue
Atomic absorption
spectrophotometry,
scanning
electron microscopy
Clothing
Visible reflectance, FT-IR
microscopy, FTRaman
Pen inks
UV–vis, LC
Plastic fragments
FT-IR, UV–vis
Tire fragments
Thermal analysis, FT-IR
Food (poisoned)
Liquid- and solid-phase
extraction, GC/MS
Fingerprints
Fluorescent visualization
Metals
Atomic absorption
spectrophotometry,
titrations
Types of physical evidence
BODY FLUIDS
Conventional serology:
presence of blood in stains
species identification and ABO
grouping
is not adequately informative to
positive identify a person
DNA analysis can associate victim
and/or suspect with each other or
with the crime scene
BLOODSTAIN PATTERNS
additional information
SEM: erythrocytes & lymphocytes
Types of physical evidence
BODY TISSUES
organ samples collected at
autopsy, including blood, urine
and stomach contents
toxicological analysis
DRUGS & CONTROLLED
SUBSTANCES
volatile compounds (ethanol, methanol,
isopropanol)
heavy metals (arsenic)
nonvolatile organic compounds (drugs
of abuse, pharmaceuticals)
miscellaneous (strychnine, cyanide)
trace drug presence, identity, and
quantity
plant materials, powders, tablets,
capsules
Black tar heroine wrapped in cellophane
Types of physical evidence
DOCUMENTS
examination
typed, handwritten and printed
materials for evidence of forgery
indented writings, obliterated or
altered writings, used carbon paper,
burned or charred paper
paper and ink analysis
handwriting comparison to
determine authenticity
Obliterated writing examination
Types of physical evidence
HAIRS
hairs analysis can
determine
human/animal
race
body area
cosmetic treatments
method of removal (crushed, cut,
burned, forcibly removed, fallen
out naturally)
can associate a hair to a person
positive identification
presence of drugs and poisons
type
color, composition construction
morphological features
DNA analysis
toxicological examination
FIBERS
Types of physical evidence
Two matching hairs identified with the
comparison microscope
Flax fibers viewed with
polarized light
Types of physical evidence
FINGERPRINTS
the strongest possible evidence
of a person’s identity
Fingerprint Matching
FIRE DEBRIS &
EXPLOSIVES RESIDUE
EXAMINATIONS
identification of accelerants and
explosive residues
Unburned accelerator liquid on a soot covered carpet
Types of physical evidence
FIREARMS & AMMUNITION
individual microscopic marks
identification, source, operability of
firearms.
detection and characterization of
gunpowder residues
muzzle-to-garments distance
estimation
GLASS FRAGMENTS
Cause of breakage
Direction of breakage force
Physical fitting
Glass fragment comparisons
Photomicrograph: test
bullet - questioned bullet
Glass fracture produced
by a high-speed projectile
Types of physical evidence
PAINT & PAINT PRODUCTS
analysis and comparison of paint
transferred from the surface of an
object to another during the
commission of a crime:
Suspect vehicle impacting a victim
vehicle; a pedestrian or a stationary
object
Tool impacting stationary object
Paint databases can help identify
the year, make and/or color of a
motor vehicle from a chip of paint
left at the scene.
Paint Layers on Wood Surface
Types of physical evidence
TOOLMARK
IDENTIFICATION
microscopic side-by-side comparison
attempts to link a particular tool with
a particular mark to the exclusion of
any other tool
Spacing between teeth in gripping -major
role in toolmark examinations
ROPE & CORDAGE
composition, construction, color and
diameter
manufacturer
Types of physical evidence
SOILS & MINERALS
comparison between two or
more soils to determine if they
share a common origin
color, texture, composition
comparison
Layers of soil exposed at a grave site. Each
layer must be sampled
WOOD
place the suspect at the crime
scene
side or end matching, fracture
matching and species
identification.
Cross-section - Xylem
Types of physical evidence
OILS/GREASE &
COSMETIC PRODUCTS
SHOEPRINTS & TIRE
TREAD IMPRESSIONS
have value for forensic
comparisons.
can provide positive
identification of the suspect’s
shoes or tires from the suspect’s
vehicle.
possess unique composition for
comparison
Shoeprint
collected
using a
gelatin lifter.
Processing physical evidence
discovering, recognizing and examining it;
collecting, recording and identifying it;
packaging, conveying and storing it;
exhibiting it in court;
disposing of it when the case is closed.
The Crime Scene
Physical Evidence
Physical evidence is any object that can establish
that a crime has been committed or can link a
crime and its victim or its perpetrator.
Forensic science begins at the crime scene. The
investigator must recognize physical evidence &
properly preserve it for laboratory examination.
The evidence must be kept in its original condition
as much as possible.
Securing the Crime Scene
Secure & Isolate the Crime Scene
First priority is medical assistance to individuals &
arresting the perpetrator.
Ropes or barricades and guards will prevent
unauthorized access to the area.
Every person who enters the crime scene has the
potential to destroy physical evidence.
The lead investigator evaluates the scene & determines
the boundaries. They do an initial walk through &
develop a strategy.
All items must be documented & photographed.
Recording the Crime Scene
3 methods of crimescene recording:
photography,
sketches, & notes
Ideally all 3 should
be used
Photography
The crime scene should be unaltered, unless injured
people are involved, objects must not be moved
until they have been photographed from all
necessary angles.
If things are removed, added, or positions changed the
photographs may not be admissible evidence.
Photograph completely
Area where crime took place & adjacent areas
Various angles
Photography
If crime scene includes a body:
Take photos to show body’s location & position relative to the
whole crime scene
Take close-up photos of injuries & weapons lying near the body
After the body is removed, photograph the surface underneath.
When size is significant, use a ruler or other measuring
scale
Digital cameras allow for enhancement & examination in
fine detail.
Videotaping a scene is also becoming popular.
Sketches
Once photos are taken, sketch the scene.
A rough sketch is a sketch, drawn at the crime scene, that
contains an accurate depiction of the dimensions of the
scene & shows the location of all objects having a bearing
on the case.
All measurements are made with a tape measure
Show all items of physical evidence
Assign each item a number or letter and list it in the legend
Show a compass heading designating north
A finished sketch is a precise rendering of the crime scene,
usually drawn to scale.
Computer-aided drafting (CAD) has become the standard.
Rough-sketch diagram of a crime
scene. Courtesy Sirchie Finger
Print Laboratories, Inc.,
Youngsville, N.C.,
www.sirchie.com.
Finished-sketch
diagram of a crime
scene. Courtesy
Sirchie Finger Print
Laboratories, Inc.,
Youngsville, N.C.,
www.sirchie.com.
Notes
Note taking must be a constant activity throughout
the processing of the crime scene.
The notes may be the only source of information to
refresh memory.
Tape-recording notes at a scene can be
advantageous – detailed notes can be taped much
faster than they can be written.
Dealing with Physical Evidence
Once found, physical evidence must be collected
& stored in a way that preserves its integrity for
forensic comparison & analysis.
The search for physical evidence must be thorough
and systematic, even when suspects are
immediately seized.
A forensic scientist is not usually needed at the
scene unless the evidence is complex or it is a
major crime.
Some police agencies have trained field evidence
technicians.
Searching the Crime Scene
One person should supervise & coordinate.
Include all probable entry & exit points in search
What to search for will be determined by the
particular circumstances of the crime.
Examples
Homicide
Hit-and-run
In most crimes, a search for latent fingerprints is
required.
Systematic Search
Collect Physical Evidence
Physical evidence can be anything from massive objects to
microscopic traces.
It may be necessary to take custody of all clothing worn by
the participants in a crime.
Handle carefully & wrap separately to avoid loss of trace evidence.
Critical areas of the crime scene should be vacuumed & the
sweepings submitted to the lab for analysis.
Mobile crime-scene vehicles carry supplies to protect the
crime scene; photo, collect, & package evidence; & develop
latent fingerprints.
Collect Physical Evidence
The integrity of evidence is best maintained when
the item is kept in its original condition as found at
the crime scene.
The entire object should be sent to the lab.
If evidence is found adhering to a large structure,
remove specimen with forceps or other appropriate
tool.
In the case of a bloodstain, one may either scrape the
stain off the surface, transfer the stain to a moistened
swab, or cut out the area of the object containing the
stain.
Collect Physical Evidence
Each different item or similar items collected at
different locations must be placed in separate
containers.
Packaging evidence separately prevents damage
through contact and prevents cross-contamination.
Autopsy Room
Medical examiner or coroner carefully examines the victim
to establish a cause & manner of death.
Tissues are retained for pathological & toxicological
examination.
The following are collected & sent to the lab:
Victim’s clothing
Fingernail scraping
Head & pubic hairs
Blood (DNA typing)
Vaginal, anal, & oral swabs (in sex-related crimes)
Recovered bullets from the body
Hand swabs from shooting victims (for GSR analysis)
Tools for Evidence Collection
Forceps
Unbreakable plastic pill bottles w/ pressure lids
Manila envelopes, glass vials, pill boxes
Paper bags are better than plastic…why?
Fire evidence must be kept in an airtight container to
prevent evaporation of petroleum residues
Clothing must be air-dried & placed in individual paper
bags.
http://www.crimescene.com/ecpi/evidence_collection.shtml
Chain of Custody
Chain of custody is a list of all people who came into
possession of an item of evidence.
Chain must be established whenever evidence is presented
in court as an exhibit.
Failure to do so may lead to ? Regarding authenticity & integrity of
evidence.
All items should be carefully packaged and marked upon
their retrieval at crime sites.
Normally, the collector’s initials & date of collection are
inscribed directly on the article.
The evidence container must also be marked with
collector’s initials, location of evidence, & date of collection.