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Bloodstain pattern analysis is directed at evaluating the bloodstain patterns found in the scene in an effort to categorize them into
an established taxonomy
Directionality is defined by
the long axis of the individual stain and the presence of scallops, tails, and small satellite spatter in the side opposite where the droplet first struck
The point of convergence is determined by
the reverse vector of the directionality of a number of stains in a pattern
A blood droplet in flight is a sphere and as a result any measurement of the diameter of the droplet will be
To determine the impact angle measure the long and short axis of the stain which will not include any
portion of the scallops or tail and then divide the short axis by the long axis.
Bloodstain pattern analysis has established classifications of stains know as the
taxonomy of stains.
Passive stains result from an action other than a directed force to a blood mass. Examples include
contact stains, dripping blood, drip trails, and blood pools or flows.
Swipes patterns are produced when a bloodied object comes in contact with
another surface with associated lateral motion
Dynamic patterns are created by
forceful events where blood is projected out from a source. They include spatter, castoff, arterial patterns, splashes, and spines
Spatter occurs when a blood mass is broken up into droplets and occur primarily as
impact spatter usually from gunshot or blunt trauma
Arterial patterns result from blood in volume that is
projected into a scene under pressure from an artery or the heart
Splash patterns occur when a volume of blood is
projected into the scene with minimal force. Splash are not typical and may be present in staged crime scenes
Void patterns occur when a
secondary object is present between a bloodstain event and a nearby surface. They most often appear in spatter events.
phenolphthalein and leucomalachite green tests are based on
an oxidation-reduction of the chemicals that occurs in the presence of heme
During the use of the phenolphthalein test if any pink color reaction occurs in the second step and prior to applying oxidizer it would indicate
a false positive.
During the use of the phenolphthalein test if an immediate pink color reaction occurs after the application of the oxidizer (hydrogen peroxide) than
the test is positive for the presence of blood.
The same procedures are followed for leucomalachite green and a
green reaction will indicate a positive test.
Chemical enhancement of latent blood using luminol and fluorescien allow the visualization of latent bloodstain patterns that are
either too light or washed up
The primary methods for enhancing latent or slightly visible bloodstain are the use of
luminol, fluorescein, amido-black and leuco-crystal violet (LCV)
Firearms examiners look at a variety of individual and class to compare the characteristics of
bullets, casings, and weapons to one another.
Beyond comparison work
firearm examiners exam the following areas to assist in reconstructing the shooting incident,: evaluate ejection patterns, gunshot residue patterns, and examination of bullet and bullet fragments
Forensic pathologists deal with terminal ballistics and consider the effect of
projectiles on the body and provide information that may assist in limiting the position of the victim at the time of wounding.
CSI deal with external ballistics they consider the
trajectory of the bullet after leaving the weapon and deal with bullet defect verification, defining the bullet angle based on defect shape, and direction of fire.
The presence of metallic lead in a suspected bullet defect is evaluated on scene using
sodium rhodizonate test (Plumbtesmo).
The presence of metallic copper in a suspected bullet defect is evaluated on scene using
DTO dithio oximide (Cuperotesmo)
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