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Blood Spatter Analysis. General Rules. Directionality of a blood drop while in flight is usually obvious from the geometry of its resulting bloodstain. The pointed end indicates the direction of travel prior to impact on a surface. General Rules.
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General Rules • Directionality of a blood drop while in flight is usually obvious from the geometry of its resulting bloodstain. The pointed end indicates the direction of travel prior to impact on a surface.
General Rules • The shape of a bloodstain is a function of the angle at which it impacts a surface. Perfectly round bloodstains result from a ninety degree impact. The angle of impact of an elliptical bloodstain may calculated from its length to width ratio.
Impact spatter: • High velocity • Medium velocity • Low velocity • Cast off Pattern • From bloody object • Arterial Spurting • From artery • Transfer Pattern • Swipe • Wipe • Passive Pattern • Gravity alone
TARGET SURFACE TEXTURE • Bloodstains can occur on a variety of surfaces, such as carpet, wood, tile, wallpaper,clothing, etc… • The type of surface the blood strikes affects the amount of resulting spatter,including the size and appearance of the blood drops.
TARGET SURFACE TEXTURE • Blood droplets that strike a hard smooth surface, like a piece of glass, will have little or no distortion around the edge.
General Rules • Surface tension prevents spattering regardless of the distance a drop of blood has fallen before impacting a smooth, hard surface such as glass.
TARGET SURFACE TEXTURE • Blood droplets that strike a fairly hard surface.. From a distance. Will show a distinct appearance. (scalloping) around the edge of the blood droplets. • And rays • And satelite drops
TARGET SURFACE TEXTURE • Surfaces such as wood or concrete are distorted to a larger extent. Notice the spinesand secondary spatter present.
Non spatter: • Transfer patterns • Swipe • wipe • Passive • Gravity only • Changes with time • Settle • Clot • Dry
TRANSFER BLOODSTAINS • Swipe: A transfer bloodstain is created when a wet, bloody object comes in contact with a secondary surface. • Wipe: An object moves through an existing stain.
PASSIVE BLOODSTAINS • Passive Bloodstains are drops created or formed by the force of gravity acting alone.
Spatter: PROJECTED BLOODSTAINS • Projected bloodstains are created when a blood source (victim) is subjected to a force • The size, shape, and number of resulting stains will depend, primarily, on the amount of force utilized to strike the blood source.
SPATTER Patterns • Spatter patterns • High velocity • Medium velocity • Low velocity • Arterial Spurting • Cast off
Arterial Spatter • Arterial Spurt / Gush • Bloodstain pattern(s) resulting from blood exiting the body under pressure from an artery (heart)
Cast Off Pattern • Cast-off Stains • Blood released or thrown from a blood-bearing object in motion
General Rules • The smaller the size of bloodspatters, the greater the energy required to produce them. Low, medium, and high velocity impact spatter may be identified by their respective sizes.
PROJECTED BLOODSTAINS - Impact • Low Velocity • Gravitational pull up to5 feet/sec. • Relatively large stains4mm in size and greater
General Rules • When the preponderance of individual bloodstains are approximately 1mm or more in diamerer, they have been produced by a medium velocity impact. Most often they would result from a beating or stabbing.
PROJECTED BLOODSTAINS - Impact • Medium Velocity • Force of 5 to 25 feet/sec. • Preponderant stain size1 to 4mm in size
General Rules • When the preponderance of individual bloodstain diameters are less than 1mm, they have been produced as a result of a high velocity impact. Most often they would result from a shooting.
PROJECTED BLOODSTAINS - Impact • High Velocity • Force of 100 feet/sec. andgreater • Preponderant stain size1mm in size and smaller • Mist-like appearance