Blood “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

Unknown Stains at a Scene Questions to be answered: Is it blood? Is it human blood? Whose is it? Determine blood type. What caused the blood spatter? Determine the method(s) in which blood may have been deposited.

Introduction Blood typing can provide class evidence; whereas DNA profiling can provide individual evidence.

Blood Characteristics Whole blood carries cells and plasma—the fluid with hormones, clotting factors, and nutrients. Shown below: Red (Erythrocyte) blood cells carry oxygen to the body’s cells and carbon dioxide away. Platelets aid in blood clotting and the repair of damaged blood vessels. White (Leukocyte) blood cells fight disease and foreign invaders and, alone, contain cell nuclei. Erythrocyte Platelet Leukocyte

Blood Typing What are the four types of blood? A, B, AB, and O What do we use to identify the blood types? ABO Blood Typing What is the population distribution in the US? Type Percent O A B AB 45 40 11 4

Blood Typing What is the difference between the types? Antigen – cells are located on the red blood cell. Antibody—are proteins secreted by white blood cells that attach to antigens to destroy them, located outside the red blood cell. Agglutination—clumping of red blood cells; will result if blood types with different antigens are mixed

Blood Group A Has A antigens on the surface of red blood cells and B antibodies in blood serum. The B antibodies will attack and destroy Type B blood cells when they are introduced into the body. Can give blood to A and AB, can received blood from O and A

Blood Group B Has B antigens on the surface of red blood cells and A antibodies in blood serum. The A antibodies will attack and destroy Type A blood cells when they are introduced into the body. Can give blood to B and AB; can receive blood from O and B

Blood Group AB Has both A + B antigens on the surface of red blood cells + NO A or B antibodies in blood serum. Will not reject or attack any blood types = Universal Recipient Can give blood to AB, can receive blood from A, B, O, and AB

Blood Group O Has NO A or B antigens on the surface of red blood cells but has BOTH A + B antibodies in blood serum. Will not “provoke” and attack by any antibodies = Universal Donor Can give blood to A, B, O, and AB; can receive blood from O

Blood Groups Type Antigen Antibody A A B A, AB O, A B, AB O , B B B A Can Give Blood To Can Get Blood From Type Antigen Antibody A A B A, AB O, A B, AB O , B B B A Neither A nor B AB A and B AB A, B, O, AB Universal Acceptor Neither A nor B O A and B A, B, O, AB O Universal Donor

* This is why we have positive (O+) and negative (B-) blood types! Rh Factor A certain blood protein was discovered while studying Rhesus Monkeys called: Rh If this protein is present in your blood, you are: Rh+ (positive). If your blood lacks this protein, you are: Rh- (negative). * This is why we have positive (O+) and negative (B-) blood types!

Presumptive Tests for Blood Determination Kastle-Meyer color test—a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink color if blood is present Hematest® tablet—reacts with the heme group in blood causing a blue-green color Luminol test—reaction with blood to produce light

Human vs Animal Blood Microscopic observation RBC in animal has a nucleus RBC in human no nucleus Frog Blood Human Blood

Human vs Animal Blood Precipitin test Blood is injected into a rabbit; antibodies are formed; the rabbit’s blood is extracted as an antiserum; the antiserum is placed on sample blood. The sample will react with human proteins if human blood is present. This test is very sensitive and requires only a small amount of blood.