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BT05.03
Discuss the use of DNA typing
and forensic anthropology in the
identification process
A.
DNA TYPING
1. What is DNA – the genetic material found
within the cell nuclei of all living things
a. Nucleus of cells contains RNA/DNA
b. DNA = deoxyribonucleic acid
c. Nucleus has 23 pairs of chromosomes
made up of DNA (in mammals, the strands of
DNA are grouped into structures called
chromosomes)
d. Within each pair, one chromosome from
sperm and one from egg
FYI
2. What makes DNA individual?
a. Four chemicals: adenine, guanine,
cytosine, and thymine
b. Chemical strung together = DNA code
c. Some sections of DNA vary from
individual to individual (with the exception
of identical twins, the complete DNA of
each individual is unique)
d. Scientists can link a strand of DNA to a
given individual
3. Criminal investigations
a. Specimens: blood, hair, bloodstained
clothing – DNA fingerprints derived from
evidence collected at the crime scene
are compared to the DNA fingerprints of
suspects. The DNA evidence can
implicate or exonerate a suspect.
.
The sample is segmented using enzymes,
and the segments are arranged by size
using a process called electrophoresis.
The segments are marked with probes and
exposed on X-ray film, where they form a
characteristic pattern of black bars – the
DNA fingerprint. If the DNA fingerprints
produced from two different samples
match, the two samples probably came
from the same person
b. Provides powerfully compelling evidence
DNA fingerprinting was first developed as an
identification technique in 1985. Originally
used to detect the presence of genetic
diseases, DNA fingerprinting soon came to
be used in criminal
investigations and forensic
science.
The first criminal conviction
based on DNA evidence in
the U.S. occurred in 1988.
• Generally, courts have accepted the
reliability of DNA testing and admitted
DNA test results into evidence. However,
DNA fingerprinting is controversial in a
number of areas: the accuracy of the
results, the cost of testing, and the
possible misuse of the technique.
• The accuracy of DNA fingerprinting has
been challenged for several reasons. First,
because DNA segments rather than
complete DNA strands are “fingerprinted,”
a DNA fingerprint may not be unique;
large-scale research to confirm the
uniqueness of DNA fingerprinting test
results has not been conducted. In
addition, DNA fingerprinting is often
performed in private laboratories that may
not follow uniform testing standards and
quality controls.
• Also, since human beings must interpret
the test, human error could lead to false
results. DNA fingerprinting is expensive.
Suspects who are unable to provide their
own DNA experts may not be able to
adequately defend themselves against
charges based on DNA evidence.
• In the United States, the Federal Bureau
of Investigation (FBI) has created a
national database of genetic information
called the National DNA Index System.
The database contains DNA obtained from
convicted criminals and from evidence
found at crime scenes. Some experts fear
that this database might be used for
unauthorized purposes, such as identifying
individuals with stigmatizing illnesses such
as acquired immunodeficiency syndrome
(AIDS).
QUESTION
• After reading this information, if you were
a juror in a murder trail and the only
evidence the prosecution had to link the
defendant to the crime was DNA evidence,
would you find the defendant guilty of the
crime?
B. FORENSIC ANTHROPOLOGY
1. SKELETAL ANATOMY
a. 206 bones in the human body
(children have 300 since they are not all
fused together yet)
b. Man = 12 pounds
Woman = 10 pounds
2. WHAT BONES SHOW
a. How person lived
b. Debilitation illnesses (rickets, polio,
healed fractures)
c. Right handed or left handed
d. Clues to occupation (for instance,
waitresses show signs of their arm
strength in their bones: their strong side
is more developed than the other side)
3. QUESTIONS ABOUT
SKELETAL REMAINS
a. Sex: women have broader pelvis, men have a
larger jaw & forehead
b. Age: joints, bones, & teeth exhibit more and
more wear as a person ages
c. Race: nose shape and shape of the eye socket
can sometimes help determine this
d. Height: determined by measuring leg and arm
bones
e. Weight: heavier people tend to wear down
certain joints in their lower body, esp. knees &
ankles
BT05.04 DISCUSS USES OF
ODONTOLOGY AND
SEROLOGY STUDIES IN
FORENSIC MEDICINE
A. ODONTOLOGY
1. Characteristics of teeth after death
a. No other part last longer
b. In fires, teeth usually only means to
ID remains
c. No two people have identical teeth
2. Requirements for identification
a. Need dental records
b. Dentists chart five surfaces of each
tooth in a grid (odontogram)
c. Can also provide “bite mark” evidence
3. Teeth useful in determining subject’s age
B. SEROLOGY
1. BLOOD TYPES
a. Four types (A,B,O, and AB)
b. Rh factor
c. Female cells have Barr Body (found as a
drumstick-shaped mass attached to one of
the nuclear lobes in polymorphonuclear
leukocytes in normal females (sex
chromatin)
2. CRIMINOLOGY
a. Kastle-Meyer test to determine if it is
indeed blood
b. Precipitin test – determines animal or
human blood
c. Can determine type and gender from
blood
d. Provides reliable and informative
evidence
FINGERPRINTS
• No two people have the same fingerprints
• Fingerprints are not inherited
• Identical twins have different ridge
patterns
• Dactyloscopy – term used for
fingerprinting
Three basic types:
1. latent – invisible to the eye. Formed by
sweat, either from the hands themselves
or by unconscious contact between the
fingers and the face or other parts of the
body where there are sebaceous glands.
(even if a criminal scrubs his hands and
dries them thoroughly, if he then puts a
hand to his face or his hair, he is likely to
leave a latent print on anything he
touches)
2. Visible – the most legible. Results from
fingers stained with blood or ink or a
similar medium. Is rarely found at a crime
scene
3. Plastic or molded – an impression made
on a soft surface such as cheese, soap or
putty
OTHER TECHNIQUES
Entomology factors
the presence of insects (& particularly
blowflies) and their form (egg, larva, pupa,
adult) can accurately calculate time of
death, because different species of insects
have specific generation times
GRID SEARCH
Search pattern used for physical evidence
collection, especially in large outdoor
areas. String, flags, &/or tape are often
used to indicate edges of search areas, or
mark out grid sections
LUMINOL:
chemiluminescent compound that, when
sprayed on even amounts of blood, reacts
with the iron in the hemoglobin and causes
the blood spot to glow with a blue light;
effective even on surfaces that have been
wiped clean of visible blood.
STRING METHOD
Bloodstain pattern analysis technique.
Establishes the source of spattered blood
by connecting stains along a series of
straight lines, based on their shape (and
thus their direction).
When enough strings have been
stretched in this way, they will converge
towards the source of the blood.
CHEILOSCOPY
• The study of lip prints
• A person’s lip prints are unique
• Use in criminal cases is limited because
the credibility of lip prints has not been
firmly established in our courts
Five basic types used by forensic
scientists are:
1.
2.
3.
4.
5.
Diamond grooves
Long vertical grooves
Short vertical grooves
Rectangular grooves
Branching grooves
RAPE KIT:
•
Used in cases where sexual assault is a
possibility. Doctor or nurse examiner
takes DNA samples to be submitted for
laboratory analysis, and records any signs
of bruising, cuts, abrasions, concussion,
and evidence of penetration.
• Typical samples include clothing, underwear,
debris, combings and /or pulling of head and
pubic hair, fingernail scrapings and/or clippings,
vaginal or penile swabs and smears, anal swabs
& smears, oral swabs, saliva or blood samples
• See Forensic Nursing video