lab exam - definitions Flashcards
surface tension
the tendency of liquid surfaces at rest to shrink into the minimum surface area possible
directionality
combination of the direction of travel and the angle of impact. It indicates the direction the blood was traveling when it impacted the target surface
angle of impact
the angle at which a blood drop strikes a surface
point of convergence
the point of intersection generated by lines drawn through the long axes of individual stains that indicates in two dimensions the location of the blood source
point of origin
the three-dimensional location from which blood spatter originated
force vs stain size relationship
the higher the force is, the smaller the bloodstain will be
projected bloodstain
created when an exposed blood source is subjected to an action or force, greater than the force of gravity
transfer bloodstain
result from objects coming into contact with existing bloodstains and leaving wipes, swipes, or pattern transfers behind
passive bloodstain
result from gravity acting on an injured body
scalloping
edge pattern. Can help indicate the height from which the drop fell and the directionality.
drip pattern
results from a liquid that dripped into another liquid, at least one of which was blood. Often surrounded by satellite stains
satellite stain
a smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface
spill pattern
result of a volume of blood that falls or spills on a surface
pool pattern
result of an accumulation of liquid blood falling at low velocity/from a low point on a surface
low velocity impact stain
external force of less than 5 fps creating stains generally 3 mm and larger
medium velocity impact stain
external force of 5 to 25 fps (force applied by a person using a tool) creating stains between 1 and 3 mm. Radial patterns are common and distributed like the spokes of a wheel
high velocity impact stain
external force applied to blood source is greater than 100 fps creating stains less than 1 mm (mist). Presence of back spatter that can go on the assailant and forward spatter from the exit wound
arterial gush
results from blood exiting the body under pressure from a breached artery. Creates somewhat of a stair-like pattern
Expirated stain
caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth, or an injury to the airways or lungs
castoff pattern
result of the centrifugal force as the weapon is swung back over the attacker’s head (tangential to arc of swing). 90° at wall and ceiling. Number of hits is always number of patterns visible + 1
swipe
pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces
wipe
an altered bloodstain pattern resulting from an object moving through a pre-existing wet bloodstain
action
the functional mechanism of a breech-loading firearm that handles (loads, locks, fires, extracts, and ejects) the ammunition cartridges, or the method by which that mechanism works
ballistic coefficient
measure of a body’s ability to overcome air resistance in flight