Analysts can tell the direction of the impacting object
by the shape of the spatter (tails point in the direction of motion)
. Counting the arcs can also show the minimum number of blows delivered. Arterial spray – refers to the spurt of blood released when a major artery is severed.
How does one determine the direction from where blood originated?
Directionality- An investigator may discern the direction of travel of blood striking an object by
studying the stain’s shape
. As the stain becomes more elliptical in shape, its direction becomes more discernible because of the pointed end of a bloodstain faces its direction of travel.
How can an investigator tell the direction of travel of blood from the shape of a bloodstain?
An investigator may discern the direction of travel of blood that struck an object by
studying the stain’s shape
. As a stain becomes more elliptical, its direction becomes more discernible because the pointed end of a bloodstain faces its direction of travel.
How can you determine the location of the blood source from blood droplets?
The location of the source of blood can be determined if there are at least two drops of blood splatter. This can be determined by
drawing straight lines down along the axis of the blood spatter and taking into account the angle of impact
. Where the lines intersect is the area of convergence.
How do you find the angle of a blood drop?
How can blood spatter tell a story?
Based on the varying sizes and shapes of the blood drops, investigators can often
tell what type of weapon caused the spatter, determine the general area where the attack occurred, and track the positions of the victim
.
What causes blood droplets to have varying shapes?
When blood is impacted, droplets are dispersed through the air.
When these droplets strike a surface, the shape of the stain changes depending on the angle of impact, velocity, distance travelled and type of surface impacted
.
How do you simulate blood spatter?
Hit the sponge sharply with the hammer
. This should result in a spatter pattern on the paper. Remove the sponge and let the pattern completely dry. If you look closely at the simulated blood drops, you will see that they form ellipses.
What does an analyst have to measure to determine the angle of blood spatter?
Using elastic string, the analyst draws lines from each spatter through the level line. Then, he or she uses
a protractor on the level line in the area where the strings converge
to determine the angle of flight for each spatter.
What does area of origin tell investigators?
The area of origin is where the pink lines intersect, indicated inside the red square. Within this area in the three dimensional space,
the impact in blood of the victim most likely occurred
. When a person is shot, for example in the head, two kinds of typical blood spatter patterns can be formed.
What is the area of origin in blood spatter?
Area of Origin –
The three-dimensional location from which blood spatter originated
. Backspatter Pattern – A bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated with an entrance wound created by a projectile.
How do you find the area of origin?
What can blood evidence determine?
Blood evidence isn’t just collected off of weapons, but can also be collected off of the floor or other surfaces in a crime scene. This blood is also tested to determine
if the blood came from the victim or the suspect
. Besides testing, investigators use blood stain patterns to help determine if a crime was committed.
How do you find the angle of impact in projectile motion?
Calculate the angle of impact with the following equation: “
i = asin (w/l)
.” Replace “w” with the length of the minor axis and “l” with the length of the major axis. “Asin” is the arcsin or inverse sine function and is available on most calculators.
How is the angle of convergence determined?
If you have a number of bloodstains, the area of convergence can be determined by
drawing lines from the leading edge of stains through the long axis
. The lines come together in a general area where the blood has emerged, helping to locate the origin of the bloodstains.
How do you calculate the angle of impact?
Use trigonometric functions to determine the impact angle for any given blood droplet. To determine the angle of impact,
take the inverse sin (arcsine) of 0.5, which is 30 degrees
.
What are the 3 types of blood spatter?
- Angle of impact. The acute angle formed between the direction of a blood drop and the plane of the surface it strikes.
- Arterial Spurting (or gushing) pattern. …
- Back Spatter. …
- Blood Spatter Analysis. …
- Bloodstain. …
- Cast-off pattern. …
- Contact stain. …
- Direction of flight.
What properties of blood determine the shape of a blood drop in flight?
The spherical shape is caused by the
surface tension
of the blood. Surface Tension causes the blood drop to pull itself in; both horizontally and vertically. The blood drop will settle into a spherical shape, as a result of the surface tension. surface.
How does distance affect blood spatter?
As the distance between the blood source and the bloodstains increase, the length of the stains increase and the width decreases
. These bloodstains will also show the direction the blood drop was traveling when it impacted the target surface.
In what direction were drops 2 and 7 traveling when they struck the surface explain your answer?
drop 2 was traveling form
right to left
when is struck surface. Drop seven was traveling from bottom to top. This can be determined because the pointed end of the spatter faces from the top, and the pointed end of a bloodstain always faces its direction of travel.
Is it blood spatter or blood splatter?
Many people use the words spatter and splatter interchangeably. If you’d like to be precise,
use spatter for small particles of liquid
. Reserve the use of splatter for large messes.
