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FORENSIC SCIENCE

Serology

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What is Serology?• Serology is the study

of serums such as blood, saliva, semen and sweat.

• A forensic serologist applies this information to criminal activity and the law.

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What is Blood?• Blood is a very

complex mixture of cells, enzymes, proteins and inorganic substances.

• The fluid portion is the plasma.

• Solids are suspended in the plasma.

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Characteristics of Blood• Blood plasma is made primarily of water and accounts for

55% of the total amount of blood content.• Three different types of cells are suspended in the plasma.

These cells are:• Erythrocytes are the red blood cells and are responsible for

carrying oxygen.• Leukocytes are the white blood cells and are responsible

for “cleaning” the system of foreign invaders.• Thrombocytes are the platelets and are responsible for

blood clotting.• Blood serum is the liquid that separates from the blood

when a clot is formed.

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Blood Questions

• When blood is found at a crime scene, several questions must be answered:

• 1. Is it blood?

• 2. If so, is it human or animal?

• 3. If human, what type of blood is it?

• 4. How did the blood fall or spatter?

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1st Question – Is it blood?• A crime scene investigator

cannot presume that every red stain or liquid is blood.

• Ketchup, spaghetti sauce and red jello may all be mistaken for blood.

• The investigator will perform presumptive tests at the scene to determine if the substance is blood.

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Two of the common Presumptive Tests are color tests.

1. Kastle-Meyer -phenolophthalein and hydrogen peroxide are mixed together and the blood’s hemoglobin will cause the formation of a deep pink color. Several household items will yield a false positive for a color test. For example, potatoes and horseradish yield a false positive. However, since these are unusual in a crime scene setting the Kastle-Meyer is a reasonable indication of blood.

The Presumptive Blood Tests

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The Presumptive Blood Tests2. Hemastix – the strip is moistened with distilled

water and then dipped into the substance. A green color indicates blood.

A third option is luminol.

3. Luminol reacts with blood to produce light instead of color. Luminol detects blood even if the area has been cleaned.

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It is blood, but is it human blood?

• At the lab, the technician will need to determine if the blood is human or animal.

• First, the technician will complete a microscopic examination.

• The red blood cells of mammals do not have a nucleus. This is an important distinction.

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Non-Mammalian Animal Blood

Frog Blood• Larger nucleic red

blood cells that undergo cell division

• No platelets

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Human Blood• Numerous non-nucleic red

blood cells--5 to 6 million per mm3

• Larger but less numerous white blood cells 5 to 10,000 per mm3

• Tiny, cellular fragments 350 to 500,00 per mm3 called platelets

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It is blood, but is it human blood?• The next test that the technician will conduct is the

precipitin test.• In this test, the blood is injected into a rabbit;

antibodies are formed; rabbit’s blood is extracted as an antiserum; the antiserum is placed on sample blood. It will negatively react with human proteins.

• This test is very sensitive and requires only a small amount of blood.

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It is human blood, but what type?

Around 1900, Karl Landsteiner discovered that there are four different kinds 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% of Caucasians, 94% of Black Americans and 99% of all Asians are Rh positive.

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Blood Type Terminology

• ABO blood groups--based on having an A, B, both or none of the factors on the red blood cell

• Rh factor--may be present on the red blood cell; positive if present and negative if not

• Antigen--a substance found on a red blood cell

• Antibody--a substance that reacts with an antigen

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

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Blood Genetic Terminology

• Genotype--letters that represent the traits; ie, AA, AO, BO, BB, AB and OO

• Phenotype--words that describe the traits• Heterozygous--different alleles for the same trait;

ie: AO, BO, AB• Homozygous--the same alleles for the trait; ie:

AA, BB, OO

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Blood Typing

• A blood type has antigen A and will agglutinate with B.

• B blood type has antigen B and will agglutinate with A.

• AB blood type has antigen A and B and will not agglutinate with either A or B.

• O blood type has neither antigen A or B and will agglutinate with either.

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Blood Reactions to Antiserum

REACTION

BLOOD TYPEAnti-A Serum Anti-B Serum

Agglutination

No agglutination

Agglutination

No agglutination

No agglutination

Agglutination

Agglutination

No agglutination

Type A

Type B

Type AB

Type O

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Blood Typing

Reactions to Anti-Serum

Blood Groups

Type Antigen AntibodyCan GiveBlood To:

Can GetBlood From

A

B

AB

O

A

B

A and B

NeitherA nor B

B

A

NeitherA nor B

A and B

A, AB O, A

B, AB O , B

AB

A, B, O, AB

A, B, O, AB

O

Only certain blood types can donate or receive blood from other blood types. If the wrong blood is transfused, the person may die.

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Population Distribution of Blood Types in the U. S.

Type Percent

O

A

B

AB

45

39

12

4

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Typing of Dried Blood StainsAbsorption-elution technique

Antiserum is placed on the blood stain. Antibodies combine with the specific antigens.

Unreacted serum is washed off the bloodstain. Stained material is heated to 56 degrees C, breaking the

antibody-antigen bond. This process is known as elution.

Known red blood cells are added. Agglutination will occur if antigens present on the added RBC’s were also originally on the stained material.

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Differentiating Within Blood Types

The determination that the blood type is O + eliminates 55% of the population. In order to narrow down the possibilities within a specific blood type, the blood is tested for certain enzymes.

Enzymes are proteins that speed up or slow down chemical reactions. Enzymes that exist in different forms are called polymorphic and can be broken down into their separate proteins called iso-enzymes.

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Commonly Used

Blood Enzymes and Proteins Adenosine deaminase AD Adenylate kinase AK Carbonic anhydrase II CA II Erythrocyte acid phosphatase EAP Esterase D EsD Glucose-6-Phosphate dehydrogenase G6PD Glyoxylase U GLO I Group-specific component Ge Haptoglobin Hp Peptidase A Pep A Phosphoglucomutase PGM 6-Phosphogluconate dehydrogenase 6PGD Transferrin Tf

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PGM--phenotypesElectrophoresis can separate the protein

components into these 10 iso-enzymes.

1- 1+ 2- 2+ 2-1- 2+1- 2-1+ 2+1+ 2+2- 1+1-

-

Three of these are most common PGM 1+, PGM 2-1+ and PGM 2

+

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EAP--phenotypesDetermined by the intensity of the fluorescence.

The darker the band the more it fluoresced.

B

C

A A BA B CB C CA

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The final question, how did the blood fall or spatter?

A group of blood spatter specialists deal with the physical properties of blood and the patterns produced under different conditions as a result of various forces being applied to the blood.

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The final question, how did the blood fall or spatter?

• Blood, as a fluid, follows the laws of physics. It is not influenced nor affected by race, gender, or age of the one bleeding.

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BLOOD DROPLETCharacteristics

• A blood droplet will remain spherical in space until it drops onto 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.

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BLOOD DROPLETVolume

• Is approximately 0.05 cc

• Is not the same for all blood droplets--from 0.03 cc to 0.15 cc

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

• The impact area is called the target.

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CONDITIONS EFFECTINGBLOODSTAIN SHAPE

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

original surface• Texture of the target surface

– On clean glass or plastic--droplet will have smooth outside edges

– On a rough surface--will produce scalloping on the edges

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Questions Answered by Blood Spatter Interpretation

• The distance between the target surface and the origin of blood at the time of blood shed

• 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.

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Questions Answered by Blood Spatter Interpretation

• 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

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Bloodstain Terminology

• Angle of impact--angle at which blood strikes a target surface.

• Bloodstain transfer--When a bloody object comes into contact with a surface and leaves a patterned blood image on the surface.

• Backspatter--blood that is directed back toward its source of energy.

• Cast-off--blood that is thrown from an object in motion

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Bloodstain Terminology

• Contact stain--general term referring to bloodstains caused by contact between a wet, blood-bearing surface and a second surface which may or may not have blood on it

– Transfer--image is recognizable and may be identifiable with a particular object

– Swipe--wet blood is transferred to a surface which did not first have blood on it

– Wipe--a non-blood bearing object moves through a wet bloodstain, altering the appearance of the original stain

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Bloodstain Terminology• Directionality--relates to the direction a drop of blood

traveled in space from its point of origin

• Terminal velocity--the greatest speed to which a free falling drop of blood can accelerate in air. It is dependent upon the acceleration of gravity and the friction of the air against the blood--approximately 25 feet/second.

– High velocity--greater than 100 feet/second; gives a fine mist appearance

– Low velocity--5 feet/second or less

– Medium velocity--5 to 25 feet/second.

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Bloodstain Pattern

• Terminal Velocity• Directionality• Angle of Impact

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Blood Stain Patterns

The shape of a blood stain: Round--if it falls straight down at a 90 degree

angle. Elliptical--Blood droplet elongates as the angle

decreases from 90 to 0 degrees. The angle can be determined by the following formula:

width = sine of the impact angle

length

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IMPACT• The more acute the angle of impact, the more

elongated the stain.• 90 degree angles are perfectly round 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.• The greater the height the drop falls the larger the

spatter.

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Height of the Droplet and Spatter Size

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Angle of Impact and Spatter Shape

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Blood Stains• 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 the stain is traveling.

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Area of Intersection

The location of the blood source can be determined by drawing lines the various blood droplets to the point where they intersect. This is the blood’s origin.

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Area of ConvergenceThe area of convergence

is the point of origin; the spot where the “blow” occurred.

It is determined by drawing a line from the area of intersection straight up to where to where the angle of impact would intersect

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CRIME SCENE

What evidence can you see in this crime scene? What story does the scene tell?

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Bring In The Dogs!The dog locates human scent. A closer look shows that the ashes have human remains and clothing. In addition, look closely at the rocks on the next slide.

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Blood Evidence

• Class evidence for blood would include blood type. If you can determine the DNA you would have individual evidence.

• Blood stain patterns are considered circumstantial evidence in a court room. Experts could argue many points including direction of stains, height of the perpetrator, position of the victim, left/right hand, whether the body was moved, etc.

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Another Body Fluid - Sperm• Among the smallest and most

highly specialized cells in the human body.

• Has a head and a tail

• Contains 23 chromosomes with the genetic material found in the head

• Males release 2.5 to 6 milliliters of seminal fluid per ejaculation with approximately 100 million sperm per milliliter. Magnified 400X

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SemenDetermination of Seminal Fluid

- Suspect stain may have stiff, crusty appearance

- Acid phosphatase color test- presumptive test– the presence of acid phosphatase, the enzyme

secreted by the prostate gland into the seminal fluid, will turn purple when sodium alpha naphthylphosphate and Fast Blue B solution are placed on it.

– It will also fluoresce under UV light when it comes in contact with 4-methyl umbelliferyl phosphate.

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Detection and Collection of Semen Sample

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Semen (cont.)Determination of Seminal Fluid• Prostate Specific Antigen (PSA) or P30--unique to

seminal plasma– P30 is isolated and injected into a rabbit where

antibodies are produced (anti-P30)

– The stain extract is placed in one well of an electrophoresis plate and the anti-P30 in the opposite well. The electric is applied and the antigens and antibodies move toward each other. The formation of a precipitation line between the wells shows the presence of P30 in the sample stain. It must be seminal fluid.

Microscopic Examination of Sperm

• A microscopic examination will also determine if the sample is semen

• The presence of spermatozoa confirms that the sample is semen

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No spermatozoa?

• The male could have oligospermia – a low sperm count

• The male could have aspermia – no sperm due to a vasectomy

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Collection of Rape Evidence• The Medical Examination: Collection of Physical Evidence

The following types of physical evidence should be collected during the medical examination for laboratory analysis:

• HAIR (both pubic and head hair)– Cannot individually identify a person unless the root is

present; – Does provide strong collaborative evidence individual was

at the crime scene; – Can be distinguished between human and animal; – May be able to determine race; and – May be able to establish the part of the body from which

the hair came.

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Collection of Rape Evidence (cont)• FIBERS

– Limited value due to mass production of clothing; and – In rare cases, can be used to deduce individual identification with

a high degree of certainty.• BLOOD

– Can be distinguished as to human or animal; and – DNA analysis can provide individual identification.

• FINGERNAIL SCRAPINGS– Used to collect DNA evidence for individual analysis and

identification.• VAGINAL, RECTAL AND ORAL SWABS AND SMEAR

– Used to collect DNA evidence for individual analysis and identification

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Secretors

• 80% of people are considered secretors. Their blood-type antigens are found in high concentration in their body fluids such as saliva, semen, vaginal secretions and gastric juice. If you are a secretor, you will have a higher concentration of A and B antigens than does your blood!!

• With the advent of DNA, the secretor evidence is not as important as it once was.