Presentation on theme: "Chapter 10 Blood Identification & Serology “Out damned spot! Out, I say Here’s the smell of the blood still, All the perfumes of Arabia will not Sweeten."— Presentation transcript:
Chapter 10 Blood Identification & Serology “Out damned spot! Out, I say Here’s the smell of the blood still, All the perfumes of Arabia will not Sweeten this little hand. Oh, Oh, Oh!” —William Shakespeare’s Lady Macbeth, in Macbeth
Chapter 10 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.
Chapter 10 Serology From 1950 to the late 1980’s, forensic serology was the most important part of lab procedures. Even with development of DNA techniques, labs still utilize basic serology testing methods to save money and time.
Chapter 103 Blood Characteristics Plasma - fluid portion of blood (55%) Serum yellowish liquid that separates from the blood when clot is formed. contains platelets and white blood cells Can be used to determine freshness of blood sample since clots within minutes of air exposure Cells (45%)
Chapter 104 Blood Characteristics Erythrocytes - red blood cells most numerous; transport gases Leukocytes - white blood cells larger than red cells and less numerous; defense Thrombocytes – platelets tiny cellular fragments; responsible for blood clotting
Chapter 105 Blood Typing ~1900, Karl Landsteiner discovered there are 4 types of human blood based on presence or absence of specific antigens. Antigen (agglutinogen): Large, globular shaped protein substance found on the surface of red blood cells that can stimulate body to make antibodies. Antibody (agglutinin): Y-shaped protein substance produced after the birth as a defense response against foreign antigens entering our body with foods, bacteria, etc, and found in plasma.
Chapter 106 Agglutination Agglutination (clumping of red blood cells) The clumped red cells crack and cause toxic reactions, possibly fatal. We don’t have antibodies against our own antigens! So, no worries! Blood clumping is an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells. Blood typing is done not only prior to blood transfusions to ensure success, but also in Forensics and in parental disputes!
Chapter 107 Blood Typing Blood type A has antigen A on the surface of the cell will agglutinate with blood type B. Blood type B has antigen B on the surface of the cell will agglutinate with blood type A. Blood type AB has antigens A and B on the surface of the cells will not agglutinate with either type A or B blood. Blood type O has neither antigen A or B and will not agglutinate.
Chapter 10Kendall/Hunt Publishing Company8 Blood Groups Type Antigen Antibody Can Give Blood To Can Get Blood From A B AB O A B A and B Neither A nor B B A Neither A nor B A and B A, ABO, A B, ABO, B AB A, B, O, AB O
Chapter 109 Population Distribution of Blood Types in the U.S. TypePercent O A B AB 45 40 11 4
Chapter 1010 Serology Terminology 1940, Landsteiner and Weiner reported discovery of Rh factor by studying blood of the Rhesus monkey. Statistics: Rh positive 85% of Caucasians 94% of Black Americans 99% of all Asians Rh factor— may be present on red blood cells; positive if present and negative if not Practice blood typing and successful transfusion: http://nobelprize.org/educational/medicine/landsteiner/landsteiner.html http://nobelprize.org/educational/medicine/landsteiner/landsteiner.html
Chapter 1011 Collecting Blood Evidence 1.Photograph carefully: from different angles, wide range to close range 2.Store blood-stained materials in carefully tagged paper/porous containers Needs air flow so mold/mildew do not develop 3.Visualize any latent blood stains 4.After carefully documenting, swab blood stains and store in sealed “vacu-tainers” for analysis
Chapter 1012 Unknown Stain at a Scene Questions to be answered: Is it blood? Is it human blood? Whose blood is it? Determine blood type, alcohol content, drugs present Determine method(s) in which blood may have been deposited
Chapter 1013 Blood Presumptive Tests Hematest® tablet— drip water over tablet onto stain or rub test strip onto a wet stain produces blue-green color Hemoglobin breaks down peroxides in reagent into oxygen which then reacts with benzidine to produce color Can give false positive with dried bleach residues and some plastics
Chapter 1014 Blood Presumptive Tests Kastle-Meyer Reagent is a mixture of phenolphthalein and hydrogen peroxide Test by swabbing stain and dripping reagent onto swab Produces deep pink color Hemoglobin breaks down the peroxides in reagent into oxygen which then reacts with reduced phenolphthalein to produce color Can give false positives with potatoes and horseradish
Chapter 1015 Blood Presumptive Tests Luminol — reagent is mixture of luminol powder, potassium hydroxide (KOH) and hydrogen peroxide (H 2 O 2 ) usually sprayed on area in dim light produces white/blue glow iron found in hemoglobin serves as catalyst for reaction may destroy DNA evidence can give false positives with certain metals (Cu, Fe, Co) and bleach is a very sensitive indicator giving results with dried or even washed blood years old
Chapter 1016 Human or Animal Blood? Microscopic observation (see next slides) Precipitin test— human blood injected into (most often) a rabbit; rabbit’s blood produces antibodies against the human blood; rabbit’s blood extracted as an antiserum antiserum is placed on unknown blood sample blood sample will agglutinate if human blood is present since antiserum has human antibodies test very sensitive; requires only small amount of blood. same test concept used to determine animal breed
Chapter 1017 Human or Animal Blood Animal (Non-Vertebrates) blood has nucleic red blood cells Frog Blood Human Blood
Chapter 1018 Secretors 80% of the population are secretors. blood-type antigens found in high concentration in their body fluids (saliva, semen, vaginal secretions and gastric juice) Would not need a blood sample therefore to determine blood type! 20% of population are “non-secretors” Cannot determine blood type from fluids
Chapter 1019 Blood as Evidence Blood type = class evidence DNA evidence = individual evidence Blood patterns = circumstantial Experts could argue many points including: direction of travel, height of the perpetrator, position of the victim, left/right hand, whether the body was moved, etc.
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