FORENSIC SEROLOGY

1
FORENSIC SEROLOGY

• Chapter 8

2
Serology

• The term serology is used to describe a broad
  scope of laboratory tests that use specific
  antigen and serum antibody reactions.
• The identity of each of the four A-B-O blood
  groups can be established by testing the blood
  with anti-A and anti-B sera.
• The concept of specific antigenantibody
  reactions has been applied to immunoassay
  techniques for the detection of drugs of abuse in
  blood and urine.

FORENSIC SEROLOGY
3
Nature of Blood

• The word blood refers to a highly complex mixture
  of cells, enzymes, proteins, and inorganic
  substances.
• Antigens, usually proteins, are located on the
  surface of red blood cells and are responsible
  for blood-type characteristics.

FORENSIC SEROLOGY
4
What makes up our blood?

• RED BLOOD CELLS (erythrocytes) The most
  abundant cells in our blood they are produced in
  the bone marrow and contain a protein called
  hemoglobin that carries oxygen to our cells.
• WHITE BLOOD CELLS (leukocytes) They are part of
  the immune system and destroy infectious agents
  called pathogens.
• PLASMA The yellowish liquid portion of blood
  that contains electrolytes, nutrients and
  vitamins, hormones, clotting factors, and
  proteins such as antibodies to fight infection.
• PLATELETS (thrombocytes) The clotting factors
  that are carried in the plasma they clot
  together in a process called coagulation to seal
  a wound and prevent a loss of blood.

5
Blood Typing

• More than 15 blood antigen systems have been
  identified, but the A-B-O and Rh systems are the
  most important.
• An individual that is type A has A antigens on
  his/her red blood cells, type B has B antigens,
  AB has both A and B antigens, and type O has
  neither A nor B antigens.
• For every antigen there is a specific antibody
  that will react with it to form clumps known as
  agglutination.
• Thus, if serum containing anti-B is added to red
  blood cells carrying B antigen, they will
  immediately react.

FORENSIC SEROLOGY
6
What are blood types?
7
Rh Factors

• Scientists sometimes study Rhesus monkeys to
  learn more about the human anatomy because there
  are certain similarities between the two species.
  While studying Rhesus monkeys, a certain blood
  protein was discovered.
• Rh factor is determined by the presence of
  another antigen, the D antigen.
• If your blood does contain the protein, your
  blood is said to be Rh positive (Rh). If your
  blood does not contain the protein, your blood is
  said to be Rh negative (Rh-).

A A-B B-AB AB-O O-
http//www.fi.edu/biosci/blood/rh.html
8
ABO and Rh Factors
Blood Type Can Donate to Can Receive from
A 34
A- 6
B 9
B- 2
AB 3
AB- 1
O 37
O- 8
9
Immunoassay

• A number of immunological assay techniques are
  commercially available for detecting drugs
  through antigen-antibody reaction.
• One such technique, the enzyme-multiplied
  immunoassay technique (EMIT), is used by
  toxicologists because of its speed and high
  sensitivity for detecting drugs in urine.
• In a typical EMIT analysis, antibodies that will
  bind to a specific drug are added to the
  subjects urine.
• Other immunoassay procedures are also available,
  such as radioimmunoassay (RIA), which uses drugs
  labeled with radioactive tags.

FORENSIC SEROLOGY
10
In the EMIT assay, a drug that may be present in
a urine specimen will compete with added labeled
drug for a limited number of antibody binding
sites. The labeled drugs are indicated by an
asterisk. Once the competition for antibody sites
is completed, the number of remaining unbound
labeled drug is proportional to the drugs
concentration in urine.
11
Antigen-Antibody Reaction

• When an animal, such as a rabbit or mouse, is
  injected with an antigen its body will produce a
  series of different antibodies, all of which are
  designed to attack some particular site on the
  antigen of interest.
• This collection of antibodies is known as
  polyclonal antibodies less specific and
  inconsistent
• A collection of antibodies designed to combine
  with a single antigen site (specific) can be
  manufactured known as monoclonals.

FORENSIC SEROLOGY
12
How can blood be used as evidence?

• Blood samples Can be analyzed to determine
  BLOOD TYPE and DNA, which can be matched to
  possible suspects.
• Blood droplets Can be analyzed to give clues to
  the location of a WOUND, movement of a VICTIM,
  and type of INJURY.
• Blood spatter Can be analyzed to determine
  PATTERNS that give investigators clues to how a
  crime might have happened.

13
Forensics of Blood

• The criminalist must be prepared to answer the
  following questions when examining dried blood
• 1. Is it blood?
• 2. From what species did the blood originate?
• 3. If the blood is of human origin, how closely
  can it be associated to a particular individual?
• The determination of blood is best made by means
  of a preliminary color test.

FORENSIC SEROLOGY
14
The Tests - 1

• A positive result from the Kastle-Meyer color
  test is highly indicative of blood.
• Hemoglobin causes a deep pink color.
• Alternatively, the luminol test is used to search
  out trace amounts of blood located at crime
  scenes.
• Produces light (luminescence) in a darkened area.
• Microcrystalline tests, such as the Takayama and
  Teichmann tests, depend on the addition of
  specific chemicals to the blood so that
  characteristic crystals will be formed.

FORENSIC SEROLOGY
15
The Tests - 2

• Once the stain has been characterized as blood,
  the precipitin test will determine whether the
  stain is of human or animal origin.
• The precipitin test uses antisera normally
  derived from rabbits that have been injected with
  the blood of a known animal to determine the
  species origin of a questioned bloodstain.
• Once it has been determined that the bloodstain
  is of human origin, an effort must be made to
  associate or dissociate the stain with a
  particular individual.
• DNA analysis has allowed forensic scientists to
  associate blood to a single individual.

FORENSIC SEROLOGY
16
Figure 8-5 
17
Stain Patterns of Blood

• The crime scene investigator must remember that
  the location, distribution, and appearance of
  bloodstains and spatters may be useful for
  interpreting and reconstructing the events that
  produced the bleeding.
• Surface texture and the stains shape, size, and
  location must be considered when determining the
  direction, dropping distance, and angle of impact
  of a bloodstain.

FORENSIC SEROLOGY
18
Bloodstain Pattern Analysis Terms

• Spatter Bloodstains created from the
  application of force to the area where the blood
  originated.
• Origin/Source The place from where the blood
  spatter came from.
• Angle of Impact The angle at which a blood
  droplet strikes a surface.
• Parent Drop The droplet from which a satellite
  spatter originates.
• Satellite Spatters Small drops of blood that
  break of from the parent spatter when the blood
  droplet hits a surface.
• Spines The pointed edges of a stain that
  radiate out form the spatter can help determine
  the direction from which the blood traveled.

19

• Bloodstain Pattern Analysis
• How can an investigator use bloodstain patterns
  to analyze a crime scene?
• Location and description of individual stains and
  patterns
• Direction a blood droplet was traveling by
  calculating angles of impact
• Area of origin of blood source or sources
• The type of object used in attack (edged, blunt,
  firearm, etc.)
• Minimum number of blows
• The positions of the victim, suspect, and objects
  during events
• The sequence of events

20

• Passive Bloodstains
• Patterns created from the force of gravity
• - Drop, series of drops, flow patterns, blood
  pools, etc.

Images from http//www.bloodspatter.com/BPATutoria
l.htm
21
Stain Patterns of Blood

• Surface texture is of paramount importance. In
  general, the harder and less porous the surface,
  the less spatter results.
• The direction of travel of blood striking an
  object may be discerned because the pointed end
  of a bloodstain always faces its direction of
  travel.
• The impact angle of blood on a flat surface can
  be determined by measuring the degree of circular
  distortion. At right angles the blood drop is
  circular, as the angle decreases, the stain
  becomes elongated.
• The origin of a blood spatter in a
  two-dimensional configuration can be established
  by drawing straight lines through the long axis
  of several individual bloodstains. The
  intersection or point of convergence of the lines
  represents the origin point.

FORENSIC SEROLOGY
22
Heredity and Paternity

• The transmission of hereditary material is
  accomplished by means of microscopic units called
  genes, located on chromosomes.
• Alternative forms of genes that influence a given
  characteristic (such as eye color or blood type)
  are known as alleles.
• Paternity testing has historically involved the
  A-B-O blood typing system, along with blood
  factors other than A-B-O.
• Currently, paternity testing has implemented DNA
  test procedures that can raise the odds of
  establishing paternity beyond 99 percent.

FORENSIC SEROLOGY
23
Testing for Seminal Stains

• Many of the cases sent to a forensic laboratory
  involve sexual offenses, making it necessary to
  examine exhibits for the presence of seminal
  stains.
• The best way to locate and at the same time
  characterize a seminal stain is to perform the
  acid phosphatase (an enzyme secreted into seminal
  fluid) color test.
• A purple color indicates acid phosphatase enzyme.
  
• Semen can be unequivocally identified by either
  the presence of spermatozoa or of p30, a protein
  unique to seminal plasma.
• Forensic scientists can successfully link seminal
  material to an individual by DNA typing.

FORENSIC SEROLOGY
24
Rape Evidence

• The rape victim must undergo a medical
  examination as soon as possible after the
  assault.
• At that time the appropriate items of physical
  evidence including clothing, hairs, and vaginal
  and rectal swabs can be collected for subsequent
  laboratory examination.
• All outer and undergarments should be carefully
  removed and packaged separately in paper (not
  plastic) bags.
• Bedding, or the object upon which the assault
  took place, may also be carefully collected.

FORENSIC SEROLOGY
25
Rape Evidence

• If a suspect is apprehended within 24 hours of
  the assault, it may be possible to detect the
  victims DNA on the males underwear or on a
  penile swab of the suspect.
• Items routinely collected from the suspect
  include all clothing, pubic hair, head hair,
  penile swab, and a blood sample or buccal swab
  for DNA typing.
• The forceful physical contact between victim and
  assailant may result in a transfer of such
  physical evidence of blood, semen, saliva, hairs,
  and fibers.

FORENSIC SEROLOGY