components of blood and their functions
erythrocytes - aka red blood cells, carry respiratory gases to all parts of the body, mainly oxygen and carbon dioxide
leukocytes - aka white blood cells, fight against disease and foreign invaders
platelets - aka thrombocytes, aid in blood clotting
plasma - the liquid portion of blood that carries proteins like hormones, antibodies, clotting factors, and nutrients


immune system terminology
antigen - examples any structure that can trigger an immune response ex: pollen
antibodies - structure and function Y shaped protein produced by the immune system that react to a specific antigen
antiserum - how it is prepared a serum containing antibodies
Withdraw blood from human vein
Inject human blood into a rabbit
Rabbit produces antibodies to human blood (antiserum)
immunoassay - technique using antibodies to bind specifically to targeted substances in order to identify their presence


how blood type is determined - to determine blood type, a sample of the blood is mixed with anti-A, anti-B, and Rh factor. Based on the reactions (coagulation), you can determine the type of blood
difference between A, B, AB and O blood types
A blood - has A antigens and Anti-B antibodies
B blood - has B antigens and Anti-A antibodies
AB blood - has A and B antigens and no antibodies
O blood - has no antigens, and anti-A and anti-B antibodies
Rh factor - antigen protein that when present will make blood positive
universal donor/receiver
Universal donor: O-
Universal receiver: AB+
percentages of each blood type in the U.S. population - O (most common in U.S.)
inheritance of blood types - parents give 50% of their DNA to their children. A and B are dominant blood types and O is recessive. Depending on whether the parents and homozygous or heterozygous for their blood type will determine what their child is
Ex: Mom - Blood type A (IAIA), Dad - Blood type B (IBi)
Blood type AB -50% chance
Blood type A - 50% chance
Blood type B - 0% chance
Blood type O - 0% chance
Karl Landsteiner - scientist that discovered ABO system of blood typing in 1901

blood as evidence
why blood is either class or individual evidence
Class evidence - can categorize by blood type
Individual evidence - if DNA is present
methods to determine presence of blood - how and when to use each
Kastle-Meyer - to test if a found liquid is blood. Phenolphthalein and hydrogen peroxide are added to stain and if the stain is blood then it will change to a deep pink
Luminol - to test in large areas and will not interfere with the DNA, luminol chemical reacts with hemoglobin and gives a fluorescent color via black light
Hemastix - strips with a chemical that when reacted with blood will turn green
Leucomalachite Green - good to use for cleaned up blood but can destroy DNA
methods to determine blood is human
precipitin test - tests for serum proteins since they are slightly different in each animal, immunoassay reaction
how surfaces affect blood spatter - smoother surfaces will result in a circular drop with minimal spikes or satellites, rough surfaces will result in an irregular shape and many spikes and satellites
effect of height on blood spatter - as you increase in height, the larger the blood drop will be and the more chance of getting spikes and satellites due to the gravity breaking the cohesive properties in blood
effect of velocity on blood spatter
Low velocity - traveling at about 5ft/second results in a 4mm size drop or greater (ex: walking, blunt impact, fist fight)
Medium velocity - traveling at about 5-25 ft/second results in a 1-4mm size drop (ex: beating, cutting, stabbing)
High velocity - traveling at about 100 ft/second results in a mist of blood less than 1mm in size (ex: gunshot, high speed machinery, explosives)
passive vs transfer vs projected blood spatter and examples
Passive blood spatter - only under the control of gravity, dripping blood or blood falling into blood
Transfer blood spatter
Contact - when a wet blood surface comes in contact with a non bloody surface ex: stepping in blood and leaving blood footprints
Swipe - a bloody object moving over a non-bloody surface ex: bloody hand moving down a wall
Wipe - a non-bloody object moving through a blood area ex: dragging an object through blood and altering its appearance
Projected blood spatter - created when the blood source is subjected to an action greater than the force of gravity

how to determine directionality of blood spatter - the direction of the blood is in the direction of the tail end of the blood drop, if there is a circle than there is no direction (90o)

measure and calculate angle of impact
Measure the length of the blood drop (not including the tail) in mm
Measure the width of the blood drop (widest part) in mm
Take the inverse sin of the width/length to get the angle of impact

determine area of convergence
Draw a line through the middle of the blood drop lengthwise and see where all the lines intercept and that is the area of convergence









measure and determine origin of height
To determine the origin of height of a blood drop, take the tangent of the angle of impact and multiply by the distance of the blood drop from the area of convergence to solve for the height



Other body fluids
Seminal fluid
Evidence used in most rape cases
Presumptive test - SAP
Confirmatory test - PSA (p30)
Saliva
Presumptive test - Iodine test (testing for presence of amylase)
Confirmatory test - Microscope test for cheek cells
Vitreous humor
Can detect disease and drug usage
Best to used for PMI (post mortem interval)
Urine
Can detect for drugs, poisons, and alcohol
Sweat
ABO blood type secretor