Test+CK

-chapter 8-blood --*there won't be anything about blood spatter --transfusion --antibodies --vocab --true false --multiple choice --short answer --expect a question from charles manson --

Types of Techniques: 1. catalytic: presumptive...might be blood or its not blood at all -visible stains --kastle meyer --hemastix nonvisible stains; -luminal

2. color tests/crystalline-confirmation test

takayama/teichmann test

Is it human?

Precriptin

What is blood made of? - mixture of cells, enzymes, proteins and inorganic substances

Plasma - the fluid portion of blood is called - mainly water; composes 55% of blood make-up

The other 45% composes the solid part of the make-up - red blood cells, white blood cells, and platelets are suspended in the plasma - white blood cells contain DNA so can tell with certainty whether blood left at crime matches blood of a suspect or victim

Platelets - aid in blood clotting and repair of damaged blood vessels

Red Blood Cells (erythrocytes) - transport oxygen and help transfer carbon dioxide - uses hemoglobin, an iron containing protein that binds oxygen - responsible for the red color

White Blood Cells (leukocytes) - responsible for defense and immunity - some surround, engulf and digest foreign invaders - others secrete antibodies - only blood cell that contains a nucleus so the only source of DNA

serum – the liquid that separates from the blood when a clot is formed

Antigens and Antibodies antigen ¬- A protein that stimulates the production of antibodies antibody - proteins secreted by white blood cells that attach to antigens

Anitgen-Antibody Response - when the immune system (white blood cells) recognizes a substance as foreign it attacks it in two ways 1. B lymphocyte (type of white blood cell) makes specific antibodies against the protein and bind the foreign substance 2. Phagocytes (type of white blood cell) engulf the invader

- there are millions of antigens on the surface of each red blood cell

- Blood antigens have been grouped into more than 15 systems depending on their relationship with one another, but the ones we will look at are A-B-O and Rh

Type O - 43% Type A - 42% Type B - 12% Type AB - 3%

Type A individuals have A antigens on the surface Type B individuals have B antigens on the surface Type AB individuals have A and B antigens on the surface Type O individuals have no antigens on the surface

Rh factor (aka D antigen) Rh positive – people having the D antigen Rh negative – people lacking the D antigen

The serum of the blood contains the proteins known as antibodies ( a protein in the blood that destroys or inactivates a specific antigen) - the antibody is bivalent – it has two sites to attach to the antigen so it creates a cross-linked network that clumps the blood together (called agglutination)

If anti-B (the antibody against the B antigen) is added to type B blood, the blood agglutinates.

Nature made it so that:

Type A blood contains anti-B but not anti-A Type B blood contains anti-A but not anti-B Type AB contains neither anti-A nor anti-B Type O contains both anti-A and anti-B

See if you understand the material by playing the following game: http://nobelprize.org/educational_games/medicine/landsteiner/

Serology – the study of antigen-antibody interactions

Blood Spatter - blood is a cohesive mixture - the molecules in the blood stick to each other - sometimes blood can overcome these cohesive interactions and form secondary droplets called satellites

Read the Blood and Spatter Chapter pdf pages 10-13 and examine the link below

Blood and Blood Spatter.pdf

http://www.nfstc.org/links/animations/images/blood%20spatters.swf

http://www.bloodspatter.com/BPATutorial.htm

www.prenhall.com/hsforensics

Forensic Characterization of Bloodstains Three questions to answer: 1. Is it blood? 2. From what species did the blood originate? 3. If the blood is human, how closely can it be associated with a particular individual?

1. IS IT BLOOD? Presumptive Tests - suggests but does not confirm the presence of blood; indicates that other tests should be performed - negative result means the substance IS NOT blood - positive result means the substance IS LIKELY blood

Types of Tests 1. Catalytic Tests

- tests based on the fact that heme can catalyze breakdown of hydrogen peroxide - usually produces a color change - specificity: some vegetable materials such as potatoes and horseradish will also turn the test pink - PROBLEM WHEN OUTDOORS - also, some metals interfere (Cu and Fe) - PROBLEM IF TESTING A VEHICLE - if test is negative and blood is NOT present; if positive then might be blood

Catalytic Detection of Visible Blood Stains Kastle-Meyer Test aka the phenolphthalein/peroxidase test

- when a blood stain, hydrogen peroxide and phenolphthalein reagent are mixed, the oxidation of the hemoglobin in the blood produces a deep pink color - sensitivity: 1:10,000 (if 1 drop of blood were present in a bucket with 10,000 drops of water, the PHTH test would still turn pink)

- Testing Method: swab the stain with a q-tip or some filter paper, add a drop of PHTH, add of drop of peroxide

Sangur sticks/Hemastix - used in the field kit - suggest if dried sample is blood - positive result = green or yellow to blue-green - Plastic strip with filter paper on tip containing TMB and peroxidase

Catalytic Detection of non-visible Blood Stains Luminol - also a presumptive test - reaction between blood and luminol produces light instead of color - sensitivity: most sensitive presumptive test - detects bloodstains diluted up to 300,000 times - luminol reagent is sprayed onto items suspected to be blood and the room must be darkened - any blood stains present produce a faint blue glow - advantage: can screen large areas quickly and does not interfere with subsequent DNA testing

Reaction: Luminol is C8H7O3N3 - luminol powder is mixed with a liquid containing H2O2 and some other chemicals (H2O2 and luminol are the major players) - the reactions needs a catalyst to accelerate the process - in this case the Fe from hemoglobin is the catalyst - also an oxidation reaction - during the reaction, luminol loses N ad H and gains O to produce 3-aminophthalate - the reaction leaves the 3-aminophthalate in an energized state as the electrons in the O atoms are in higher energy orbitals - as the electrons fall to a lower energy level the extra energy is released in the form of light

Chemiluminescent Reaction Scheme

source: http://www.howstuffworks.com/luminol.htm

2. Color Tests/Crystal Tests - confirmation test

- heme from the hemoglobin molecule forms a crystal when reacted with certain substances hemoblobin - Fe containing molecule in RBC that binds oxygen and carries it from the lungs to tissues

hemoglobin.bmp

Microcrystalline Tests - 2 common tests: Teichmann Test and Takayama Test

- small amount of blood added to microscope slide - chemical solution added - slide heated to form hemoglobin crystals (a pink crystal complex) - crystals can be viewed under a microscope

- positive results indicate blood - sensitivity: 0.001 mL of blood/0.1 mg hemoglobin - 20 year old blood stains have given positive results

IS IT HUMAN BLOOD???

Precipitin Test - Used to determine if the blood is of human or animal origin - Basis: animals injected with human blood form antibodies against the blood - the antibodies can be recovered by bleeding the animal and isolating the blood serum - the antibodies recovered from the animal blood interact with the antigens in the human blood and clump
 * the serum is really human antiserum

Most common Precipitin Test is the Precipitin Ring test - human blood is layered on top of the animal serum containing the human blood antibodies - the interaction between the antibodies and the antigens forms a cloudy ring at the interface of the two liquids

http://diverge.hunter.cuny.edu/~weigang/Images/18-03_precipitin_1.jpg

IS THE BLOOD RELATED TO THE CRIME OR A PARTICULAR INDIVIDUAL'S BLOOD? Gel Diffusion