Unit 5 Forensic Serology

Blood and Forensics Karl Landsteiner in 1901 discovered that not all human blood was the same He came up with a classification system of A, B, AB, O In recent years we have abandoned the A, B, AB, O typing system in forensics It has been replaced with DNA (Deoxyribonucleic acid) testing

Blood Mixture of cells, enzymes, proteins, and inorganic substances Plasma – fluid portion of the blood  Mostly water  In the plasma are several types of cells Red blood cells (erythrocytes) – carry oxygen White blood cells (leukocytes) – fight infection Platelets – help with clotting  Serum – the liquid that separates from the blood when a clot is formed

Antigens Antigens – found on the surface of red blood cells  Give the red blood cells specific characteristics Example: A, B, AB, O Rh factor – if people have it they are Rh positive, those that don’t have it are Rh negative

Antibodies Antibodies – found in the blood serum  A protein  There is an antibody for each antigen  Antiserum – blood serum that contains specific anitbodies  Agglutination – one antibody is attached to more then one red blood cell Red blood cells clump together as a result If you are type A you have anti-B, If you are type B you have anti-A, Type O has both anti-A and anti-B, AB has neither anti-A or anti-B

Blood typing Serology – the study of anitgen-antibody reactions Whole blood typing is the most widely used application  anti-A and anti-B are used to type blood  Type A blood is agglutinated by anti-A  Type B blood is agglutinated by anti-B  Type AB blood is agglutinated by both anti-A and anti- B  Type O blood is not agglutinated by either anti-A or anti-B

AB is universal recipient because it doesn’t have anti-A or anti-B antibodies O is universal donor because it has no antigens

Immunoassay Test done to detect antibodies to specific substances When the body is exposed to foreign matter it produces antibodies to fight off the foreign bodies They have detected antibodies for specific substances by injecting them into animals and then collecting the antibodies the animals make and make serums Serums are added to urine specimens are designed to react with different types of drugs

Forensic Characterization of blood stains Questions a criminalist must answer when examining dried blood Is it blood? What species did the blood originate from If the blood is human how closely can it be associated with a particular individual?

Color Test Hemastix strips – moistened with distilled water and placed in contact with a suspected blood stain. If there is blood present the strip turns green. Phenolphthalein or the Kastle-Meyer test is used to detect blood  Works because hemoglobin posses peroxidase-like activity  Peroxidase are enzymes that acclerate the oxidation of organic compounds with peroxide  A bloodstain, phenophtahalein, and hydrogen peroxide mixed together make a pink color

Luminol Produces light Spray luminol on suspected area and any bloodstains produce a faint blue glow known an luminescence Capable of detecting blood that has been cleaned up Does not interfere with DNA testing

Bloodstain Patterns Location, distribution, and appearance of bloodstains and spatter helps to reconstruct the events that caused the bleeding

Some Important things to consider when trying to trace the direction, dropping distance, and angle of impact of a blood stain: Surface texture – the harder and less porous the surface the less spatter, there are standards for comparison Can tell what direction the blood traveled based on the shape of the stain  Pointed end always faces the direction it traveled

The origin of the blood can be determined by drawing a straight line through the long axis of several bloodstains. Where these lines intersect is where the blood originated from. Can measure the impact of the angle of the blood on a flat surface by measuring the degree of circular distortion of the stain.  A drop of blood striking at a right angle is nearly circular  As the angle decreases from ninety degrees the stain elongates

Characterization of Semen First you have to locate the seminal stain Stain must be tested to prove its identity

Testing for Seminal Stains Acid phosphatase test: Acid phosphatase is an enzyme that is secreted by the prostate gland into the seminal fluid Can be detected with an acidic solution of sodium alpha naphthylphosphate and fast blue B dye Can also be detected by 4-methyl umbelliferyl phosphate will flouresce under uv light (MUP) Moisten a filter paper with water and rub it over the suspected area and then add the chemicals to the filter paper It should turn a purple color if it is positive Useful when searching large fabrics or garmets

Microscopic examination of semen: Identified by the presence of spermatozoa Spermatozoa are slender, elongated, and have a head and a tail Stained material is immersed in a small amount of water The water is rapidly stirred to transfer spermatozoa to water A drop of water is put on a microscope and stain is added There is a large amount of spermatozoa in semen so there should be a good chance of finding them However spermatozoa tend to bind tightly to clothing and are extremely brittle and dry and tend to disintegrate if the stain is washed or rubbed against another object Oligospermia – low sperm count Aspermia – no spermatozoa in their seminal fluid

Prostate Specific Antigen (PSA)  A protein found in seminal plasma  p30 is injected into rabbits to make antibodies  The serum is collected and used to test semen stains  The suspected semen is placed in one end of an electrophoresis gel  The serum is placed at the other end of the gel  Electric potential is applied and if they move toward each other a line forms midway between them

Collection of Rape Evidence Contact between victim and assailant may result in a transfer of physical evidence such as blood, hair, semen, and fibers To protect evidence all outer garments and undergarments from the people involved should be carefully removed and packaged separately in paper (not plastic) bags. Have the person disrobe while standing on a paper sheet to collect material that may fall

Carefully fold paper to keep materials inside Do not bend or rub an object with a suspected semen stain on it because it could flake off The rape victim must undergo a medical examination using a rape kit

The following items are collected when examining a rape victim: Pubic combings Pubic hair reference samples External gential dry-skin areas Vaginal swabs and smears Cervix swab Rectal swabs and smear Oral swabs and smear Head hairs Blood sample Fingernail scrapings All clothing Urine specimen

Items collected from a suspect: Clothing worn at time of assualt Pubic hair combings Pulled head and pubic hair refernce samples Penile swab Blood sample or buccal swab

Timeline Motile sperm generally survive for up to four to six hours in the vaginal cavity Nonmotile sperm may be found for up to three days after intercourse and sometimes up to 6 days later Seminal acid phosphatase decreases with time after intercourse with little chance of finding it after 48 hours Spermatozoa and acid phosphatase in the vaginal cavity should determine when and if sexual activity occurred.