UNIT 5 CH 10 BLOODSTAIN PATTERN ANALYSIS

what are the 3 questions to be answered for an unknown red stain at a crime scene?

is it blood? is it human blood? whose blood is it?

what can effect the shape of a blood droplet?

velocity, surface, and contact

swipe

created from a moving source onto an unstained surface

wipe

created when an object moves through an existing stain

what can a forensic scientist learn from a blood stain?

blood type, alcohol levels, drug levels, how the blood expelled, the pattern, and the position

what test can determine blood?

luminol test

what test can determine human blood?

precipitin test

how is the precipitin test done?

blood is injected into a rabbit and then extracted. then, if the sample reacts with the human proteins then it is human blood.

why is the precipitin test a good test?

blood can be old and only requires a small amount of blood

what dynamics does blood have?

fluid

what are questions answered by blood spatter investigation?

how the bloodstains were formed

what are passive bloodstains caused by?

the force of gravity

what are projected bloodstains caused by?

when the victim is subjected to blows by a force greater than gravity

what are transfer bloodstains caused by?

when an object contaminated with blood comes in contact with another surface

how are arterial spurts different from expiratory blood?

arterial spurts result from an artery, but expiratory is when blood is blown out from the nose or mouth

how can the direction of travel be determined by looking at a blood stain?

by the tail

blood drops

as the height of the ORIGIN ( where the blood drop originates) increases, the diameter of the impact for the blood drop will increase

low velocity spatter

object is moving less than 5 feet/ seconds- drops will be 4mm or greater

medium velocity spatter

blood drop diameters are in one to three mm in size, the speed of the object/ blood have been in the range of 5 to 25 ft per second (ex: hammer to strike someone)

high velocity spatter

stains are 1mm, the blood was traveling more than 100fr per second. the stain will look like a dried mist and will be consistent with a gunshot (ex: spatter from a gunshot wound)

what are some color tests to determine if it's blood?

hemastix, kastle meyer, luminol