Blood Out damned spot Out I say Heres

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!” —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 45 A 40 B 11 AB 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 antibodies = Universal Donor • Can give blood to A, B, O, and AB; can receive blood from O

Blood Groups Antibody Can Give Can Get Blood From Type Antigen A A B A, AB O, A B B A B, AB O, B AB A and B Neither A nor B AB A, B, O, AB Neither A nor B A and B A, B, O, AB O Universal Acceptor O Universal Donor Blood To 11

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.