Forensic Ch 8 - blood spatter

Agglutination

Clumping of microorganisms or blood cells, typically due to an antigen-antibody interaction/reaction.

Antibodies

Proteins secreted by white blood cells that attach to antigens, keeping them from harming the body. Y-shaped proteins that attach to particular kinds of antigens to destroy them (secreted by WBC)

Antigen-antibody response

reaction in which anti-bodies attach to specific antigens; causes agglutination in cross blood-type transfusions

Antigens

any foreign substance or cell in the body that reacts with antibodies (trigger the attack of antibodies in the immune response). foreign substances that trigger the attack of antibodies in the immune response

Cell-surface protein

Proteins embedded in the cell membrane used for cell transport

Lines of convergence

a two-dimensional view of the intersection of lines formed by drawing a line through the main axis of at least two drops of blood that indicates the general area of the source of the blood spatter

point of origin

a three-dimensional view formed using lines of convergence and angles of impact of at least two different drops of blood to identify the source and location of blood splatter (tangent angle of impact)

Red Blood Cells

erythrocytes - donut-shaped cells that carry oxygen throughout the body

satellite drop of blood

secondary drop formed when some blood breaks free from the main contact drop of blood

White blood cells

leukocytes - cells that police the body by destroying foreign materials.

Rh factor

presence or lack of antigens on the surface of red blood cells, which causes a reaction between Rh-positive blood and Rh-negative blood

ABO blood typing

Method of identifying which self-recognition proteins of types A and B are at the surface of an individual's red blood cells; the absence of either type is designated O.

Plasma

liquid portion of blood which contains platelets

Platelets

thrombocytes which carry out the fundamental task of healing through clotting.

Spines

the pointed edges of a stain that radiate out to form the spatter. More present on a non-smooth surface. Indicates the blood dropped at an angle.

Blood spatter analysis

a field of forensic science that deals with the physical properties of blood and the patterns produced under different conditions as a result of various forces applied to the source of blood

blood spatter patterns

Helps establish the events that took place; help distinguish between an accident and foul play.

list the types of blood spatter patterns:

Passive fall

Arterial spurts

Splashes

Smears

Trails of blood

Pools or blood

surface tension

the force that acts on the surface of a liquid and that tends to minimize the area of the surface

cohesion

Attraction between molecules of the same substance

adhesion

An attraction between molecules of different substances

ELISA blood Test

a common laboratory testing technique that detects and counts certain antibodies, antigens, proteins and hormones in bodily fluid samples. This includes blood, plasma, pee, saliva (spit) and cerebrospinal fluid (CSF). "ELISA" stands for "enzyme-linked immunosorbent assay

Luminol

the most sensitive chemical test that is capable of presumptively detecting bloodstains diluted to as little as 1 in 100,000; its reaction with blood emits light and thus requires the result to be observed in a darkened area. Blue glow when contact w blood

composition of blood

55% plasma, 45% formed elements - plasma, red blood cells, white blood cells, platelet

red blood cell function

transport oxygen and carbon dioxide

white blood cell function

Phagocytosis (neutrophils and monocytes) and antibody formation (lymphocytes) - kills bacteria and viruses

Define Red Blood Cells

erythrocytes; the most abundant cells in our blood, they are produced in the bone marrow and contain a protein called hemoglobin which carriers oxygen to our cells. Responsible for the transmission of carbon dioxide waste back to the lungs.

Define White Blood Cells

leukocytes; they are part of the immune system and destroy infectious agents called pathogens.

define plasma

this is the yellowish liquid portion of the blood that contains electrolytes, nutrients, and vitamins as well as hormones, clotting factors and proteins such as antibodies to fight infection.

define platelets

thrombocytes, the clotting factors that are carried in the plasma. They clot together in a process known as coagulation to seal a wound and prevent loss of blood.

coagulation

process of blood clotting

how many liters of blood does an average adult have?

5 liters, 7-8% of body weight

What is considered a living tissue?

Blood

list what blood does:

carries oxygen and nutrients to all parts of the body, carries CO2 and waste to the lungs, kidneys and liver, fights against infection, and help heals wounds

how many RBC are there in 2-3 drops of blood?

1 billion

For every ___ red blood cells there are platelets and WBC

600;40;1

When are blood types established?

before birth by specific genes inherited by parents, you inherit one gene from your father and one from your mother

agglutinogens

antigens on the surface of the RBC that is the basis for blood typing based on composition arrangement

when was blood typing discovered?

1900

who discovered blood typing?

Karl Landsteiner

what does blood typing do (basic terms)

identifies the presence or absence of particular proteins embedded on the cell

Why is blood typing used frequently

it is quicker and cheaper than dna profiling

what type of evidence is blood

class evidence (can link and exclude suspects from crimes)

List the Blood types

A+, A-, B+, B-, AB+, AB-, O+, O-

list the blood types from most common to least common

O (43%), A (42%), B (12%), AB (3%)

How many people have the rhesus factor?

85%

universal recipient

Type AB blood

universal donor

Type O blood

Blood transfusion

whole blood or cells are taken from a donor and infused into a patient

whole blood or cells are taken from a donor and infused into a patient

blood falling directly to floor at 90 degree angle will produce circular drops, w secondary satellites

Arterial Spurts

Found on walls or ceilings, Large patterns under pressure from an artery, but with less volume; distinct rises and falls of blood pressure apparent. Caused by pumping action of the heart

Splashes

A bloodstain pattern created from a large volume of liquid blood falling onto a surface

smears

left by bleeding victim depositing blood as he or she touches or brushes against a wall or furniture

spurt

trails of blood left by a bleeding victim as he/she moves from one location to another. Droplets are round or smeared

pool of blood

occurs when blood collects in a level (not sloped) and undisturbed place

Harder less porous surface

the less spatter results

rough surfaces

irregularly shaped stains with serated edges and satelite spatter

list harder surfaces

glass, paper, hardwood

List rougher surfaces

carpet, tile, cloth

directionality of the angle of impact

The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel

gunshot spatter

bloodstain characterized by fine forward spatter from an exit wound and backward spatter from an entrance wound

cast off spatter

created when a blood-covered object flings blood in an arc onto a nearby surface

arterial spray spatter

caused by an injury to the heart or a main artery and the pressure of the continuing pumping

a void pattern

An area within a deposited spatter pattern that is clear of spatter, caused by an object or person blocking the area at the time of the spatter's deposition.