T. Trimpe 2006 . Serology Serology is the examination and analysis of body fluids. A forensic serologist may analyze a variety.

T. Trimpe 2006 http://sciencespot.net/

Serology

Serology is the examination and analysis of body fluids. A forensic serologist may analyze a variety of body fluids including saliva, semen, urine, and blood. From 1950 to the late 1980s, forensic serology was a most important part of lab procedures. With the development of DNA techniques, more time, money, and significance were placed on developing DNA labs. However, with limited funds and the time required for DNA testing, most labs still use many of the basic serology testing procedures.

Historical Perspective of Blood TypingAround 1900, Karl Landsteiner discovered that there are four

different types of human blood based on the presence or absence of specific antigens found on the surface of the red blood cells.

In 1940, Landsteiner and Weiner reported the discovery of the Rh factor by studying the blood of the Rhesus monkey. 85 percent of Caucasians, 94 percent of African Americans, and 99 percent of all Asians Americans are Rh positive.

Blood TerminologyABO blood groups—based on having A, B, both, or no antigens on

red blood cells

Rh factor—may be present on red blood cells; positive if present and negative if not

Antigen—a substance that can stimulate the body to make antibodies. Certain antigens (proteins) found in the plasma of the red blood cell’s membrane account for blood type.

Antibody—a substance that reacts with an antigen

Agglutination—clumping of red blood cells; will result if blood types with different antigens are mixed

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.

What makes up our blood?

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

What makes up our blood?

PLASMA – The yellowish liquid portion of blood that contains electrolytes, nutrients and vitamins, hormones, clotting factors, and proteins such as antibodies to fight infection.

What makes up our blood? White Blood Cells (leukocytes) – they are

part of the immune system and destroy infectious agents called pathogens

Blood Facts

There are about one billion red blood cells in two to three drops of blood. For every 600 red blood cells, there are about 40 platelets and one white cell.

You blood type These two genes determine your blood type

by causing proteins called AGGLUTINOGENS to exist on the surface of all of your red blood cells.

http://www.lanecountyblood.org/images/other/bloodfacts.jpg

45%

40%

11%

4%

How common are the 4 blood types?

BLOOD GENETICS

Blood Genetics

The human ABO gene is on chromosome 9.

Everyone has two copies of chromosome 9 so you have two ABO genes.

One copy is inherited from our mother, the other from our father.

Alleles

There are three versions (called “alleles”) of this blood type gene: A, B, and O.

A person’s blood type is determined by which allele he/she inherits from each parent.

Pheno vs. Geno

The genetic makeup of an organism is called the “genotype”.

The “phenotype” is the visible properties of an organism.

In this case, the A, B, and O allele combination a person has is their genotype

Their blood type is their phenotype.

Determining the Genotype

The blood type gene has three different alleles:

IAIA is Type A IAIB is Type AB

IBIB results in Type B ii is Type O

Determining the Genotype Scenario:

Mom has the alleles IAIA for blood type and Dad has the alleles IBIB blood type.

What will be the blood type for their child?

Practice

Suppose that a mother has blood Type A and genotype IAi and the father has blood Type B and genotype IBi. Draw a Punnett square to show the possible genotypes of their children.

What are the phenotypes of the kids?

Stats

 O+ 1 in 3 persons O- 1 in 15 persons A+ 1 in 3 persons A- 1 in 16 persons B+ 1 in 12 persons B- 1 in 67 persons

AB+ 1 in 29 persons AB- 1 in 167 persons

Can Blood Be Individualized?

Is based on the typing of proteins and enzymes. Blood proteins have subtypes.

Most people are familiar with at least one common polymorphism in blood: Hb, which causes sickle-cell anemia.

You can also extract DNA from it.

Number of people with a blood type 3 surface antigens as probability

1. Determine % of people with that surface antigen

2. Determine the ratio by dividing 100 by the %

3. Multiple the ratios together

4. Obtain the # of people out of 100 with those 3 antigens

DATA Type of Blood % of People

A 41

B 10

AB 4

O 45

Rh + 85

Rh - 15

M 30

N 22

S 48

Determine the likelihood… 1. Of an individual with Type A, N and Rh –

2. Of an individual with Type AB, S and Rh +

3. Of an individual with Type O, M, Rh -

Blood Typing

Blood type A has antigen A on the surface of the cell and will agglutinate with blood type B.

Blood type B has antigen B on the surface of the cell and will agglutinate with blood type A.

Blood type AB has antigens A and B on the surface of the cells and will not agglutinate with either type A or type B blood.

Blood type O has neither antigen A nor B and will not agglutinate.

What are blood types?

http://learn.genetics.utah.edu/units/basics/blood/types.cfm

There are 3 alleles or genes for blood type: A, B, & O. Since we have 2 genes, there are 6 possible combinations.

Blood Types

AA or AO = Type ABB or BO = Type B

OO = Type OAB = Type AB

Rh Factors The presence of the

protein, or lack of it, is referred to as the Rh (for Rhesus) factor.

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-

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

Blood Typing Use the results shown to determine the blood type for each sample.

- = absent

+ = present

Bloodstain Pattern Analysis

How can blood be used as evidence?

Blood spatter – Can be analyzed to determine PATTERNS that give investigators clues to how a crime might have happened.

Objectives of Bloodstain Pattern Analysis

Can provide information about:Origin of bloodstainObjects that produced bloodstainDistance from bloodstain to targetPosition of victim and assailantMovement of victim and assailantNumber of blows/shots

Physical Properties of Blood Viscosity

Thickness of a liquid Surface tension

Adhesion○ Attractive forces between unlike molecules

Cohesion○ Attractive forces between like molecules

Capillary action○ When surface tension causes a liquid to be drawn

up in opposition to gravity

Size of Bloodstain

Shape of BloodstainOn impact with hard, smooth, nonporous surfaces (tile, glass)

○ Little to no distortion of stain○ Surface tension of blood drop resisting rupture

On impact with rough/textured, porous surfaces (concrete) Disrupts surface tension of blood drop

• Stain will exhibit distortion, irregular shapes, and spiny edges

– Spines = pointed edges of bloodstains that radiate away from the center of the stain

• May also see satellite spatter

Angle of Impact

A spherical drop of blood impacting a horizontal surface should create a circular stain

A drop of blood impacting a nonhorizontal surface creates a more elongated or elliptical stain due to the blood “skidding” across the target surfaceThis allows you to make 2 determinations

○ Directionality of stain○ Angle of impact

Directionality

Parent Stain with tail pointing

in direction of travel

Tail of cast off stain points

back to parent stain

Angle of Impact

The more acute the angle of impact = the greater the elongation of the stain Length increases and width decreases

By accurately measuring the length and width of the bloodstain then, the angle of impact can be calculated using the following equation:

Angle of Impact = arc sin (width/length)

Angle of Impact

ARC SIN = Width (a) 1.5cm Length (c) 3.0cm

Points of Convergence

Points of Convergence

Bloodstain Categories 3 Categories

Passive○ Only acted on by gravity and friction

Spatter○ Subject to some force other than gravity and friction

Altered○ Stains whose physical appearance has been changed in

some way

Classification of Spatter Bloodstains

Low-Velocity Impact Spatter Less than 5 ft/sec Blood spots 4-8 mm in diameter

Medium-Velocity Impact Spatter– 5-100 ft/sec– Blood spots 4 mm in diameter or less

High-Velocity Impact Spatter– Over 100 ft/sec– Blood spots 1 mm in diameter or less

Altered Bloodstains

Diffusion

ID THE STAIN

Unknown Stain at a Scene

Questions to be answered:

Is it blood?

Is it human blood?

Whose is it?

Determine blood type, alcohol content, drugs present

OVERVIEW Presumptive Tests for Blood Determination

Kastle-Meyer color test—a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink color if blood is present

Hematest tablet—reacts with the heme group in blood, causing a blue-green color

Luminol test—reaction with blood to produce light

The Kastle-Meyer Test

When blood, phenolphthalein and hydrogen peroxide are mixed, the hemoglobin in the blood will cause the normally colorless phenolphthalein to a bright pink color

This test can yield some false positives Certain vegetable matter can produce

the bright pink positive (such as potatoes)

Other blood detection tests

Doctors use Hemastix© strips to detect blood in urine

But these strips can be used at a crime scene to detect fresh or dried blood.

One simply moistens them with distilled water and wipes the bloodstain

A color change to green is a positive indicator of blood

Bayer Hemastix©

Luminol Luminol is a chemical that exhibits

chemiluminescence, with a striking blue glow, when mixed with an appropriate oxidizing agent. It is a white to slightly yellow crystalline solid that is soluble in water and most polar organic solvents.

Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide in water is used as the activator.

In the presence of a catalyst such as an iron compound, the hydrogen peroxide is decomposed to form oxygen and water:

What do you see with luminol?

It glows a bright blue in the dark, when it comes in contact with blood

Advantages of using Luminol Allows one to detect stains that would

not be ordinarily be visible Extremely sensitive - can use it in very

dilute concentrations This allows the CSI to spray large areas

with it It does not interfere with DNA, so a CSI

can collect samples for DNA analysis even after it was sprayed with luminol.

Bloody Footprints that were wiped

Luminol glows even in the presence of certain other fluids – semen, feces, bleach, tonic water, etc.

So we know it’s blood – but is it human? The Precipitin Test

Rabbits injected with human bloodThey make antibodies in their

serumThey are bled and the serum

recoveredThe serum is called human

antiserum, because it will react to human antigens

It will cause coagulation when mixed with human blood

Precipitin Test

(Human blood)

(Human antiserum made in rabbits)

Gel Diffusion Test Antigen (blood) and antibodies (human

antiserum from rabbits) are placed in separate wells in a gel.

They are forced to move towards each other.

If they bind to each other, they form a single line of precipitate in between the wells

This is a positive for human blood