The distance from the area of convergence to the drop of blood can easily be measured. To determine the point of origin, or height from the impact surface, further calculations are necessary. By measuring the width and length of a single drop of blood, the
angle of
impact can be assessed.
What method is used at the crime scene to determine the area of origin?
Spattered blood
may allow for the determination of an area or location of the origin of the blood source when the spatter-producing event occurred. If found on a suspect’s clothing, spattered blood may place that person at the scene of a violent altercation.
What method is used to determine the area of origin for a blood spatter pattern?
The location of the area of convergence and the angle of impact for each bloodstain is used to approximate this area. A common method for determining the area of origin is
the string method
.
How are blood patterns determined?
When drops of blood hit the floor at an angle, they produce elliptical stains, where their width-to-length ratio gives that impact angle. Traditionally practitioners of blood-pattern analysis trace a
straight-line from the stain at the
impact angle to reveal where the blood originated.
What are the two most common methods for documenting blood patterns?
Name and describe two methods for documenting bloodstain patterns.
Grid method
– setting up a grid of squares of known dimensions over the entire pattern using string and stakes. All overall, medium-range, and close-up photographs are taken with and without the grid.
Does Luminol only show blood?
Typically, luminol
only shows investigators that there might be blood in an area
, since other substances, including household bleach, can also cause the luminol to glow.
What are the different blood spatter patterns?
Bloodstains are classified into three basic types:
passive stains, transfer stains and projected or impact stains
. Passive stains include drops, flows and pools, and typically result from gravity acting on an injured body. … Typically, forward spatter is a fine mist and back spatter is larger and fewer drops.
What is the difference between area of convergence and area of origin?
Area of Convergence – The area containing the intersections generated by lines drawn through the long axes of individual stains that indicates in two dimensions the
location
of the blood source. Area of Origin – The three-dimensional location from which blood spatter originated.
At what angle do you think each blood droplet was dropped at?
If you examine a blood droplet that struck a surface straight-on (at a
90o angle
from the surface), the droplet is generally round. Straight-on impacts on hard, smooth surfaces produce round droplets with smooth edges. Higher velocities and rougher surfaces produce drops with more ragged edges.
What is the difference between forward spatter and back spatter?
With back spatter,
tiny blood droplets are projected
in the direction of the shooter. With forward spatter, small drops of blood travel along with the bullet through the opening where the bullet leaves the body.
Who analyzes blood evidence?
Forensic scientists who analyze bloodstain evidence are typically called
bloodstain pattern analysts
. It is best if the bloodstain pattern analyst is present at the crime scene to begin the investigation, but it is possible to use photographs, video, and reports from a crime scene investigator for the analysis.
Is blood spatter individual evidence?
– blood type. Individual evidence narrows a suspect down to a single individual. … -Blood spatter- Droplets
and patterns can reveal key evidence
such as the type of weapon that was used in the crime, the time of the crime, and other details.
What blood spatter can tell you?
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 are the six types of blood spatter patterns?
- 1902, Dr. John Glaister described 6 patterns: a. …
- circular drops. b. arterial gusheswalls or ceilings produced by.
- pumping action of the heart. c. splashesshaped like exclamation points;аused to.
- d. smearsleft when victim or suspect touches surface. e. …
- smears. f. poolsperson remains in one place bleeding heavily.
What are the 4 types of passive bloodstains?
- Passive Bloodstain. Passive Bloodstain on a rough surface (such as wood or concrete)
- Projected Bloodstain. Projected Bloodstain, possibly a Cast-Off Pattern or a HVIS.
- Transfer Bloodstain.
What can flow patterns tell you?
Flow Pattern- A bloodstain pattern formed by the movement of small or large amounts of blood as a result of gravity’s pull. … The photographs and sketches can also point out specific stains used in
determining the direction of force
, angle of impact and area of origin.
