Forensic Serology: Blood

Written By: Alice YangPeriod 7

Instructor Mary Villani

The Forensic SerologistThe forensic serologist studies body fluids such as semen, saliva, and

blood mainly for identification purposes.

Role(s): •Establishing type and

characteristics of blood•Blood testing•Examination of bloodstains•DNA typing•Preparation of court testimony & evidence

Blood Evidence

Blood is the most well-known andsignificant evidence in the moderncriminal justice system.

Blood evidence is important to the forensic

investigator because:•It can link a victim to a suspect (Locard’s Exchange Principle]•Bloodstain patterns can reveal a

great deal about position and movement

during the crime•It has managed to destroy self-

defensearguments of suspects

Forensic Value of Blood

In forensic science, blood has always been

considered class evidence. However,

individualized blood evidence is possible

in the near future. In fact, in some cases,

forensic serologists were able to link a

single perpetrator to a bloodstain with

strong probability estimates.

Nature of Blood: General CharacteristicsBlood is a slightly alkaline fluid that circulates throughout our bodies, nourishing our cells, and transporting oxygen and waste. The fluid portion

of blood consists of plasma and serum,

whilethe non-fluid portion consists of red

blood cells.

Blood is composed of:•Water•Cells•Enzymes•Proteins•Other inorganic substances

Nature of Blood: Serum

Serum is characterized by its yellow hue,

and contains white blood cells and platelets. Forensic analysts are able todetermine the freshness of a blood

sample by examining serum because it clotsseveral minutes after exposure to air.

A centrifuge can be used to separate the clotted material from the serum

portion. In addition, serum contains antibodies , proteins floating in blood fluid, which

havesignificant forensic implications.

Nature of Blood: Red Blood Cells

Red blood cells, the most prevalent blood

cells in the human body, are the primary

means of delivering oxygen from the lungs

to the body’s tissues via the blood. For red

blood cells, the forensic analyst searches for smaller chemical

substances residing on their surfaces, such asantigens , which also tend to have important forensic implications.

Blood Grouping

The A-B-O system of blood typing was discovered in 1901 by Dr. Karl

Landsteiner. During the late 1930s, a series of antigen-antibody reactions were discovered in blood, the most common ones being ABH, MN, Rh, and Gm. There

are more than 256 antigens, and twenty-

threeblood group systems based on

associationwith these antigens. A fundamentalprinciple of serology is that for every antigen, there exists a specific antibody.

In fact, all blood groups are defined by the antigens on their red blood cells and theantibodies in their serum.

Blood Typing

Blood typing requires two antiserums: anti-A and anti-B. By inserting a droplet

of these antiserums in samples of blood,

one can determine which samples maintain

a normal appearance and which samples become clotted, or agglutinated, under microscopic examination. Type-A blood

will be agglutinated by anti-A serum; Type-

B blood will be agglutinated by anti-B

serum; Type-AB blood by both; and Type-O

blood by neither.

Rh Factor

Blood can also be categorized using the Rh

(Rhesus disease) factor.  If an individual has a positive Rh factor, this means

that his/her blood contains a protein that is also found in Rhesus monkeys.  Approximately 85% of the population

has a positive Rh factor, and doctors are

trained to monitor closely any woman who is

Rh negative and becomes pregnant. The

Rh factor, like other antigens, can be found

onthe surface of red blood cells. 

Individualization of Blood

The potential for the individualization of

blood is based on the typing of proteins and

enzymes. Blood proteins and enzymes have

the quality of being polymorphisms or

iso-enzymes , which means they exist in

several forms and variants. Most people

are familiar with at least one common polymorphism in blood: Hb, which

causessickle-cell anemia.

SecretorsIn 1925, a blood-related discovery

valuable to forensic science was made. Approximately eighty-percent of the

human population was found to be "secretors," individuals whose specific types of antigens, proteins, antibodies, and enzymes characteristic of their blood

can be found in other bodily fluids and tissues.  In the case of a secretor, investigators can conclude the blood

type by examining the saliva, teardrops, skin tissue, urine, or semen. In a rape case,

for example, where the perpetrator is a secretor, potential suspects can be narrowed down through blood type analysis.

Bloodstain Analysis: The General Questions

During bloodstain analysis, the forensic

investigator uses these five specific questions as guidelines for

determining the nature of a crime.

1. Is the sample blood?2. Is the sample animal blood?3. If the sample is animal blood, from

what species did it come from?4. If the sample is human blood, what

typeis it?5. Can the sex, age, and race of the

source of blood be determined?

Bloodstain Analysis: Blood or not?To determine whether or not blood is present at a crime scene, forensicinvestigators use color or crystalline tests. In the past, police investigators weretrusted to verify the presence or absence of blood, but Miller v. Pate (1967) enforced

that physical tests should be completed in the search for blood. The Benzidine test was widely implemented until it was discovered to be a known carcinogen. The current Kastle-Meyer test, which uses the chemical, phenolphthalein, operates on the fact that when phenolphthalein comes in contact with hemoglobin, it releases peroxidase enzymes that cause a bright pink color to appear. 

Bloodstain Analysis: Blood or not?

In order to detect invisible bloodstains, forensic investigators use the luminol

test. Luminol, a chemical sprayed on carpets and furniture, reveals a slightly phosphorescent light in the dark where bloodstains (and other stains) are

present. Long-dried blood has a tendency to crystallize, or can be made to crystallize with various saline-acid mixtures. The names of various crystal tests are the Teichman test , the Takayama test , and Wagenhaar test. 

Bloodstain Analysis:Animal Blood?

To determine whether blood at the crime scene originated from an animal, forensic investigators use antiserum or gel tests. Establishing whether or not blood is animalblood is significant because any possibility of an injury to the household pet, caused by a perpetrator or another animal, must be eliminated. Pets generally spread humanbloodstains throughout the crime scene, but the pet can be a victim, perpetrator, or witness (through the cross transfer of evidence between the animal’s DNA and the perpetrator). Veterinary forensics may be anecessary unit if pets are involved in the crime.

Bloodstain Analysis:Animal Blood?

To determine whether blood is animal or human in origin, the precipitin test isconducted. This process involves injecting an animal, usually a rabbit, with human blood. The rabbit's body creates anti-human antibodies, which are then extracted from the rabbit's serum. If this antiserum is then placed on a sample

fromthe crime scene, and the blood displays clotting, the forensic investigator can conclude that the blood is human blood. The same procedure of creating and extracting antiserum can be applied to every known animal.

Bloodstain Analysis:Human Blood?

To confirm whether blood is human in origin, the forensic investigator must first determine that he has an adequate and quality blood sample. A blood sample that meets these requirements can undergo direct typing using the A-B-O system. If severely dried stains are uncovered, indirect typing should be completed using techniques such as the absorption-elutiontest. During this test, the forensic scientist adds compatible antiserum antibodies to a sample, heats the sample to break the antibody-antigen bonds, and finally inserts known red blood cells from standard blood groups to see what coagulates.

Bloodstain Analysis:Age, Sex, & Race

To estimate the age, sex, and race using

blood found at the crime scene, the forensic scientist uses various color

and nitrate tests, and applies heredity principles to his tests. Unfortunately,

no exact determinations are possible. However, clotting and crystallization

can help approximate age, testosterone

and chromosome testing can help

determine sex, and certain racial genetic markers involving protein and enzyme tests can help establish race.

Blood & Crime Scene:Wet vs. Dry Blood

Wet blood is more significant than dried blood because the forensic scientist canperform more tests in order to gain

insight to the happenings of the crime. For example, alcohol and drug content can

be determined from wet blood only. Blood begins to dry after three to five minutes

of exposure to air. As it dries, it changes

color from a deep red towards brown and

black. Blood can be categorized into pools,

drops, smears, or crusts.

Projection of BloodForensic investigators can

determine howblood was projected from the body

by examining factors such as: Type of injuries The order in which the wounds

were received Whose blood is present The type of weapon that caused

the injuries Whether the victim was in

motion or lying still when the injury was inflicted

Whether the victim was moved after the injury was inflicted

How far the blood drops fell before hitting the surface where they were found.

Blood & Crime Scene:Categories of Blood Patterns

Pools of blood have evidentiary value in collecting a wet sample. Drops of blood

can reveal the height and angle from which

the blood fell onto the surface. According to forensic scientists, the blood spatter analysis claims that blood which falls perpendicular to the floor from a

distance of zero to two feet would create a

circular drop with slightly frayed edges. Drops

froma higher distance would have more

distinct tendrils extending off the edges.

Blood & Crime Scene:Categories of Blood PatternsA blood smear on the wall or floor can indicate the direction of force of the blow.  The direction of force is always in thedirection towards the tail, or smaller end, ofthe smear. In other words, the largest area of the smear is the point of origin. Blood crusts must be tested with crystalline techniques to verify that they are actually blood. Refrigerated red blood cells have ashelf life of about forty-two days, and the serum containing white blood cells can berefrigerated much longer, almost up to a year.  DNA can be extracted from blood (if white blood cells which always contain a nucleus are present), and also from sperm,bone marrow, tooth pulp, and hair roots.

Blood & DNA TestingBlood is used in DNA testing, as shown by the following steps:1. Blood samples are collected from thevictim, defendant, and crime scene.2. White blood cells are separated from

red blood cells.3. DNA is extracted from the nuclei of

whiteblood cells.4. A restrictive enzyme is used to cut fragments of the DNA strand.5. DNA fragments are put into a bed of gel with electrodes at either end.6. Electric current sorts DNA fragments by length.7. An absorbent blotter soaks up the

imprint; it is radioactively treated, and an X-ray photograph, called an autoradiograph, is produced.

Blood & Crime Scene

Regardless of what type of analysis is used

on the blood at the crime scene, care must

be taken to handle it properly and to prevent putrefaction.  Photographs and notes should be taken before any blood

is lifted.  Samples should not be exposed

to heat, moisture, or bacterial

contamination,because these factors can shorten the survival time of proteins, enzymes, and antigens.  Delays in bringing samples to

the lab must be avoided at all cost, because

it can diminish evidential value.

Court Significance

Experts in bloodstain examination are usually law enforcement personnel. In certain jurisdictions, a police investigatoror blood specialist may testify on the

coreissue because blood evidence is usually avital aspect of the crime scene.

An expert in bloodstain examination has:•Completed specialized training•Conducted a sufficient number ofexaminations•Accumulated enough reference patterns to reinforce an argument

ReferencesDatahttp://www.crimelibrary.com/criminal_mind/forensics/serology/3.htmlhttp://www.policensw.com/info/forensic/forensic6a.htmlImagesSlide 1:

http://www.fbi.gov/hq/lab/fsc/backissu/oct2004/images/2004_10/kienker02.jpgSlide 2:http://www.separationsnow.com/FCKeditor/UserFiles/Image/

sepNOW_ezines_2006/0602_dep.jpgSlide 3: http://www.fdle.state.fl.us/CrimeLab/images/dna%20feathered.jpgSlide 4:http://www.ecmagazine.net/Winter0607/winter06webphotos/Blood%20Serum.PgSlide 5: http://www.freewebs.com/soaring_sphincter_travel_agency/red%20blood

%20cells.bmp

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http://www.dnr.state.md.us/education/horseshoecrab/2005art/testtube2.jpgSlide 9: http://science.uwe.ac.uk/projectshowcase/blood_cells%20copy.JPGSlide 10: http://www.ljmu.ac.uk/MKG_Global_Images/testtube_blood.jpgSlide 11: http://www.ronsmithandassociates.com/bloodstain.jpgSlide 12: http://www.ct.gov/dps/cwp/view.asp?a=2155&Q=315022&PM=1Slide 13: http://static.howstuffworks.com/gif/luminol-crimescene.jpgSlide 14: http://wwwimage.cbsnews.com/images/2007/12/18/image3627828g.jpgSlide 15: http://diverge.hunter.cuny.edu/~weigang/Images/18-03_precipitin_1.jpgSlide 16: http://www.eko.de/~eko_web/img_files/mibi_top3.jpgSlide 17: http://library.thinkquest.org/04oct/00206/images/bloodanalysis.JPGSlide 18: http://www.wagnerandson.com/images/drop114.jpg

ReferencesSlide 19:http://upload.wikimedia.org/wikipedia/en/thumb/0/0d/

BPA_ellipse_example.jpg/350px-BPA_ellipse_example.jpgSlide 20:

http://content.answers.com/main/content/wp/en/a/a7/BPA_AOI.jpgSlide 21: http://bodmas.org/blog/images/secondary_wavelet_spatter.jpgSlide 22: http://www.spaceflight.esa.int/users/images/gbf/ep-trom-

samp.jpgSlide 23:http://www1.istockphoto.com/file_thumbview_approve/4166625/2/

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