blood spatter

a blood spatter pattern provides

the truthfulness of an account by a witness or a suspect; origin of the blood; the angle and velocity of impact; the type of weapon used

who discovered blood typing

karl landsteiner

what does blood typing do

identifies the presence or absence of particular protein embedded in the cell

what are enzymes

complex protein that catalyst different biochemical reaction

what are satellite droplets

when blood falls from a height, or at high velocity, it overcomes its natural cohesiveness, and separates from the main droplet

what are spiking patterns

form around the droplet edges when blood falls onto a less than smooth surface

the shape of an individual drop of the blood provides what

clues to the direction from where it originated from

lines of convergence

two or more blood splatters can pinpoint then location of the blood source

blood accounts for about __ total body weight

8%

about how much blood volume loss internally or externally is required to produce what

40% or 1.5 liters; irreversible shock or death

properties of blood gravity:

pulls it to ground; droplet become longer than wide

properties of blood: cohesion

blood mixture is attracted to similar blood mixture and stick together, not separates as it falls; causes droplet to stay together

properties of blood: adhesion

attractive forces of two different objects; starts as teardrop because of adhesion

properties blood: surface tension

the elastic like property of the surface of the liquid that it tend to contract, caused by the forces of attraction between the molecules of the liquid; formation of a sphere

density

mass per unit

density of water

1000 kg/m3

the density of blood is proportional to the

protein concentration or cellular component of blood and is influenced only to a minor extent by other ions that are dissolved in the plasma

density of blood plasma is approximately

1025 kg/m3

density of blood cells circulating in the blood

1125 kg/m3

average density of whole blood for a human is about

1060 kg/m3

flat surface

edge of blood drop appears smooth and circular; glass marble

porous surface

edge of drop of blood may form small spikes or satellites

passive fall

Blood falling directly to floor at 90-degree angle will produce circular drops, with secondary satellites being more produced if surface hits is textured

what does luminol do

a reagent that reacts with the iron found in hemoglobin to cause luminescence and will show up the finest traces of blood

what causes small velocity spatter

fist fights, boots, and baseball bats

what causes medium velocity spatter?

knives

what causes high velocity spatter

bullets

what is arterial bleeding

causes spurts of blood caused by the contractions of the heart

what are cast off patterns

are created when blood is flicked off a moving object such as a baseball bat

what can a investigator determine when analyzing a crime scene

height of killer; type of bleeding; Whether the victim was sitting, lying or standing during the attack

• The type of weapon used and the type of injury caused

• Where in the room the victim was attacked and if he was moved afterwards

• The track of the blood curve can reveal if the assailant was right or left-handed

• The amount and pattern of blood can reveal if the attack was short and quick or long and frenzied

what are the steps used whenever calculation is involved

• Identify stains that have a common area of convergence.

• Draw lines through the central long axis of the stain away from the direction of travel.

• Identify the area of convergence.

• Measure the distance (cm) from the back edge of the stain to the area of convergence.

• Calculate the angle of impact of each of the stains (measure width and length of stains in mm and apply the formula).

• Use a minimum of 3 stains.

if a person is bleeding and in motion will their blood drop straight down

no they will fall to the ground at an angle

what is the point of convergence

all the blood spatters can be located by drawing an extended line and locate the point of intersection of all the lines; a string can be pinned on each blood splint and raise it following its angle of impact

once you determined the area of convergence

you will measure the distance from the area of convergence to the edge of the drop of blood when it first impacted a surface