(FSY) Forensic Serology Module Overview

Forensic Serology Module Overview 

When a stain is found at the scene of a crime, the first thing that has to be determined is whether the stain is blood. Forensic serology is the science that deals with blood and body fluids to determine if it is human and if it can be traced to a particular source. In addition to serological testing, blood spatter analysis can provide valuable information to help reconstruct the events at a crime scene to support or refute statements made by the suspect, the victim, or witnesses.

Essential Questions

    1. In what ways does serological evidence help solve a crime?
    2. What type of information can be determined from a drop of blood?
    3. How is blood typing done?
    4. What information can we get from blood stain patterns?
    5. How is blood analyzed in the Forensic lab?
    6. How is paternity established through blood testing?

Key Terms

  1. Serotology - The science that deals with the properties and reactions of serums, especially blood serum.
  2. Antigens - A substance that stimulates the immune system to manufacture antibodies (immunoglobulins). The function of antibodies is to fight off intruder cells, such as bacteria or viruses, in the body. Antigens stimulate the blood to fight other blood cells that have the wrong antigens. If a person with blood type A is given a transfusion with blood type B, the A antigens will fight the foreign blood cells as though they were an infection.
  3. Antibodies - Any of various proteins produced in the blood in response to the presence of an antigen. By becoming attached to antigens on infectious organisms antibodies can render them harmless or cause them to be destroyed.
  4. Genes - A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.
  5. Alleles - One of two or more alternative forms of a gene at the same site in a chromosome, which determine alternative characters in inheritance.
  6. Genotype - An organism's genetic makeup.
  7. Phenotype - The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
  8. Presumptive Testing - Also known as preliminary tests, screening tests or field tests. These tests establish the possibility that a specific bodily fluid is present, but they do not conclusively prove the presence of a specific substance.
  9. Kastle-Meyer Color Test - Also known as a Phenolphthalein test. A Phenolphthalein solution is used to show the possible presence of blood based upon a peroxidase reaction of hemoglobin which produces a pink color. This is a presumptive test.
  10. Precipitin - An antibody in blood that combines with an antigen to form a solid that separates from the rest of the blood.
  11. Red Blood Cells - Red cells, or erythrocytes, carry oxygen from the lungs to your body's tissue and take carbon dioxide back to your lungs to be exhaled.
  12. White Blood Cells - White blood cells (leukocytes) are one of the body's defenses against disease. Some white cells travel throughout the body and destroy bacteria, some produce antibodies against bacteria and viruses, and others help fight malignant diseases. This is where DNA is gathered from blood samples.
  13. Platelets - Platelets, or thrombocytes, are small, colorless cell fragments in the blood whose main function is to interact with clotting proteins to stop or prevent bleed.
  14. Plasma - Plasma is a fluid, composed of about 92% water, 7% vital proteins such as albumin, gamma globulin, anti- hemophilic factor, and other clotting factors, and 1% mineral salts, sugars, fats, hormones and vitamins.
  15. Whole Blood - Whole blood contains red cells, white cells, and platelets (~45% of volume) suspended in plasma (~55% of volume).
  16. Hemoglobin - The iron-containing respiratory pigment in red blood cells of vertebrates, consisting of about 6 percent heme and 94 percent globin.
  17. Confirmatory Testing - Conclusively identify the identity of a biological material.
  18. Luminol - A chemical compound that is used in solution or sprayed onto suspected surfaces. This compound gives a strong blue fluorescence when viewed with a UV light. The Luminol reacts with hematin, a substance formed as bloodstains age, and produces a luminescence which is best observed in the dark. The luminescence lasts for several minutes and can be photographed. Aged bloodstains tend to give more intense and longer-lasting luminescence than fresh blood, and can be re-sprayed with Luminol to be viewed again. This is a presumptive test.
  19. Serum - The clear, pale yellow liquid that separates from the clot in the coagulation of blood serum.
  20. Agglutination - The clumping together of red blood cells or bacteria, usually in response to a particular antibody.
  21. Immunoassay Techniques - A laboratory method for detecting a substance by using an antibody reactive with it.

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