Blood Analysis

spatter

blood which has been dispersed as a result of force applied to a source of blood

blood spatter analysis

examination of the shapes, locations, and distribution patters of bloodstains to interpret physical events which created them.

what info can we get from blood spatters?

• position of victim (sitting, standing, lying down)

• evidence of struggle

• prove or deny people’s statements

two properties of blood

blood volume and surface tension

how much of body weight does blood account for?

8%

how much blood loss causes incapacitation?

30%

how much blood loss causes shock and death?

45%

what is surface tension

elastic property of surface of the liquid that causes it to contract

3 types of spatter patterns

passive/non-contant, transfer/contact, projectile

what are passive/non-contact patterns

drops created or formed by the force of gravity acting alone

types of passive patterns

parent drops, satellite spatter

spine

what are parent drops

a drop of blood from which a wave, cast-off, or satellite spattter is caused

what is satellite spatter

small droplets of blood that are distributed around a drop or pool of blood as a result of the blood impacting the target surface

spine of blood

pointed or elongated stains which radiate away from the central area of a bloodstain

what are transfer/contact patterns?

a bloodstain pattern created when a wet, blood surface comes in contact with a second surface

what are the types of transfer patterns

wipe and swipe

wipe pattern

when there is a wet blood on a surface and something NOT blood soaked is run across

swipe pattern

when a blood soaked item is run across a non-blood soaked surface

examples of transfer patterns

writing in blood, hair swipes, footwear, and fabric impressions

what are projectile patterns?

created when an exposed blood source is subjected to an action or force greater than the force of gravity

types of projectile patterns

arterial spurt, cast-off stains, impact spatter

arterial spurt

resulting from blood exiting the body under pressure from a severed artery

cast-off stains

blood released or thrown from a blood bearing object in motion

impact spatter

created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood

what are the types of impact velocity

low, medium, high, expirated

low impact velocity meaning

large stains (4+mm in size)

medium impact velocity meaning

stain size 1-4mm often from beating

high impact velocity meaning

stain size <1 mm in size often from gunshot or high powered machinery

expirate blood

blood that is blown out of nose, mouth or wound (<1mm in size)

what impacts blood drying time

volume, surface, environmental factors

factors that impact drop size

drop height, drop angle, impact velocity

drop height

the higher the height, the larger the drop and more spines

drop angle

larger the angle the more elliptical the drop