SerologyChapter 12

Serology

• It is the study of body fluids • Blood• Saliva• Semen• Urine

Functions of Blood

• Blood has 3 main functions• Transportation

• Oxygen, carbon dioxide, wastes, nutrients, heat, & hormones

• Regulation• Ph, body temperature, water content

• Protection• From disease & loss of blood

Characteristics of Blood

• Thicker than H2O and flows more slowly

• 100.4 F temp• Ph of 7.4• 8% of body weight• Blood volume

• Male- 5-6 liters• Female- 4-5 liters

Components of Blood

• Blood consists of• 55% plasma• 45% cells

• 99% RBC (red blood cells)• <1% WBC (white blood cells) and platelets

Plasma

• 90% H2O

• 7% plasma proteins• Albumin- maintain blood osmotic

pressure• Globulin- form antigen- antibody

complexes• Fibrinogen- for clotting

• 3% other substances• Electrolytes, nutrients, hormones, gases,

waste products

Formed Elements of Blood

• Red blood cells (erythrocytes)• White blood cells (leukocytes)• Platelets (thrombocytes)• Serum

Formation of Blood Cells

• Blood cells need to be replaced continuously• Die within hours, days, or weeks• Process is called hematopoiesis

• In embryo, occurs in yolk sac, liver, spleen, thymus, lymph nodes, & red bone marrow

• In adult- occurs in red bone marrow of sternum, ribs, skull, & pelvis

Red Blood Cells (RBC)

• Contains hemoglobin (carries oxygen)• Gives it its red color• Makes up 1/3 of cell’s weight

• Is biconcave• Increased sa:vol• Flexible for narrow passages• No nucleus or organelles (no cell division)

• In adult• Male- 5.4 million RBC/gttp (drop)• Female- 4.8 million RBC/gttp

White Blood Cells (WBC)

• Are leukocytes• Have a nucleus and no hemoglobin• Classified as granular or agranular

based on presence of granules in the cytoplasm• Granulocytes- neutrophils, eosinophils,

basophils• Agranulocytes- monocytes, lymphocytes

Platelets

• Disc shaped• No nucleus present• Normal count

• 150000- 400000 gttp/blood

• Other blood cell counts• 5 million RBC• 5-10000 WBC

Serum

• Is the liquid that separates from the blood when a clot is formed

Immunoassay Techniques

• Are available for detecting drugs through antigen-antibody reactions

• 2 types of processes• EMIT (enzyme multiplied immunoassay

technique)• Antibodies that bind to a specific drug are

added to a subject’s urine

• RIA (radioimmunoassay)• Uses drugs labeled with radioactive tags

Antigen-Antibody Reactions

• When an animal 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• Called polyclonal antibodies

• Antibodies designed to combine with a single antigen site can be manufactured• Called monoclonal antibodies

Forensics of Blood

• The criminalist must be prepared to answer the following questions when examining dried blood• Is it blood?• From what species did the blood

originate?• If the blood is of human origin, how

closely can it be associated to a particular individual

• Detection of blood is best made by means of a preliminary color test

Presumptive Tests for Blood Determination

• 3 tests• Kastle-Meyer color test

• Is a mixture of phenolphthalein and hydrogen peroxide

• Hemoglobin of blood will cause a deep pink color if blood is present

• Hematest tablet• Reacts with the heme group in blood

causing a blue-green color

• Luminol test• Reacts with blood to produce light

Human vs. Animal Blood

• Once the stain has been characterized as blood, the precipitin test will determine whether the stain is of human or animal origin• Uses antisera normally derived from

rabbits that have injected with the blood of a known animal to determine the species origin of a questioned bloodstain

• Once the bloodstain has been determined to be of human origin, the blood is typed

The Discovery of Blood Types

• Before Landsteiner’s discovery, countless people died from blood transfusions• There was an assumption back then that

everybody had the same blood

• In 1900, Landsteiner proved that there are four different types of blood based on the presence or absence of specific antigens on the surface of RBC’s• Known as ABO blood group

• In 1940, he discovered the Rh factor

Blood Types

• RBC surfaces are marked by genetically determined glycoproteins & glycolipids• Agglutinogens or antigens• Distinguishes at least 24 different blood

types• Most common= ABO & RH

ABO Blood Groups

• Based on 2 glycolipid antigens (A & B) found on the surfaces of RBC• Antigen A only= type A blood• Antigen B only= type B blood• Both antigens= type AB blood• No antigens= type O blood

• Plasma contains antibodies or agglutinins to the A or B antigens not found in your blood• Anti- A antibody reacts with antigen A• Anti-B antibody reacts with antigen B

Breakdown of ABO Blood Types

• Type A- 42% • Type B- 12%• Type AB- 3%• Type O- 43%

Rh Factor

• Antigen was discovered in rhesus monkey• Called Rh antigen or D antigen

• People with Rh agglutogens on RBC surface are Rh+ (normal plasma contains no anti-Rh antibodies)

• Antibodies develop only in Rh- blood type & only with exposure to the antigen

Breakdown of Rh Blood Type

• Rh+- 85%• Rh- - 15%

• Of the Rh+ population, 85% are Caucasians, 94% are African Americans, and 99% are Asians

Universal Donors and Recipients

• People with type AB blood are called universal recipients• No antibodies present• Can receive blood from anybody

• People with type O blood are called universal donors• No antigens present• Can donate blood to anybody

Typing and Cross Matching of Blood

• Mixing of incompatible blood causes agglutination (visible clumping)• Formation of antigen- antibody complex that

sticks cells together• Not the same as blood clotting

• Typing involves testing blood with known antisera that contains antibodies A, B, or Rh+

• Cross matching is to test by mixing donor cells with recipient’s serum

• Screening is to test recipient’s serum against known RBC’s having known antigens

ABO vs. DNA

• Prior to the advent of DNA typing, bloodstains were linked to a source by ABO bloodtyping

• DNA analysis has allowed forensic scientists to associated blood and semen stains to a single individual

Blood Spatter Evidence

• It is a field of forensic investigation which deals with the physical properties of blood and the patterns produced under different conditions as a result of various forces being applied to the blood

• Follows the laws of physics

Blood Pattern Reconstruction

• What to look for at the crime scene• Stain condition• Pattern• Distribution• Location• Directionality

• What you get from blood evidence• Genetic marker

typing• Age determination• Source

determination• Race determination• Sex determination

Blood Spatter

• CSI’s must remember the location, distribution, and appearance of bloodstains and spatters• Useful in interpreting and reconstructing

the events that produced the bleeding

• Surface texture and the stain’s shape, size, and locating must be considered when determining the direction, dropping distance, and the angle of impact of a bloodstain

Blood Droplet Characteristics

• A blood droplet will remain spherical in space until it collides with a surface

• Once a blood droplet impacts a surface, a bloodstain is formed

• A droplet falling from the same height, hitting the same surface at the same angle, will produce a stain with the same basic shape

Blood Droplet Volume

• A droplet contains approximately 0.05 mL of fluid

• It is not the same for all blood droplets, but is generally between 0.03 mL to 0.15 mL

• Is directly dependent upon the surface or orifice from which it originates

• The impact area is called the target

Conditions Affecting Shape of Blood Droplet

• Size of the droplet• Angle of impact• Velocity at which the blood droplet

left its origin• Height• Texture on target surface

• On clean glass or plastic• Droplet will have smooth outside edges

• On a rough surface• Will produce scalloping on the edges

Questions Answered by Blood Spatter Interpretation

• The distance between the target surface and the origin of blood

• The point(s) of origin of the blood• Movement and direction of a person or an

object• The number of blows, shots, etc causing the

bloodshed and/or the dispersal of blood• Type and direction of impact that produced

the bloodshed• The position of the victim and/or object

during bloodshed• Movement of the victim and/or object after

bloodshed

Bloodstain Terminology

• Parent drop• The droplet from which a satellite

spatter originates.

• Satellite spatters• Small drops of blood that break off from

the parent spatter when the blood droplet hits a surface

• Spines • Pointed edges that radiate out from the

spatter

Bloodstain Terminology

• Angle of impact• Angle at which blood strikes a target

surface

• Bloodstain transfer• When a bloody object comes in contact

with a surface and leaves a patterned blood image on the surface

• Backspatter• Blood that is directed back toward the

source of energy

Bloodstain Terminology

• Cast off• Blood that is thrown from an object in

motion

• Directionality• Relates to the direction a drop of blood

traveled in space from its point of origin

Bloodstain Terminology

• Contact stain• Bloodstains caused by contact between a wet

blood-bearing surface and a second surface which may or may not have blood on it

• 3 types• Transfer

• An image is recognizable and may be identifiable with a particular object

• Swipe• Wet blood is transferred to a surface which did not

have blood on it

• Wipe • A non-blood bearing object moves through a wet

bloodstain, altering the appearance of the original stain

Bloodstain Terminology

• Terminal velocity• It is the greatest speed to which a free

falling drop of blood can accelerate in air

• Is dependent on the acceleration of gravity and the friction of the air against the blood- 25.1 ft/sec• 3 types

• High velocity- greater than 25 ft/sec, usually 100 ft/sec; gives a fine mist appearance

• Medium velocity- 5-25 ft/sec• Low velocity- 5 ft/sec or less

Bloodstain Patterns

• Round• If it falls straight down at a 90 degree

angle

• Elliptical • Blood droplet elongates as the angle

decreases from 90 to 0 degrees• Angle can be determined by the

following formula• Impact angle= sin-1 (arcsin) x (width/length)

Impact

• The more acute the angle of impact, the more elongated the stain

• 90 degree angles are perfectly round drops with 80 degree angles taking on a more elliptical shape

• At about 30 degrees, the stain will begin to produce a tail

• The more acute the angle, the easier it is to determine the direction of travel

Bloodstain Patterns

• The harder and less porous the surface, the less the blood drop will break apart

• The softer and more porous the surface, the more a blood drop will break apart

• The pointed end of the blood stain faces the direction of travel

Area of Intersection and Convergence

• The location of the blood source can be determined by drawing lines from various blood droplets to the point where they intersect

• The area of convergence is the point of origin• The spot where the blow occurred

Blood Evidence

• Class evidence for blood would include blood type• If you can determine the DNA, you

would have individual characteristics• Blood stain patterns are considered

circumstantial evidence in a court room• Experts could argue many points

including direction of travel, height of the perpetrator, position of the victim, left/right hand, whether the body was moved, etc