Presentation on theme: "Blood Spatter Analysis. General Rules Directionality of a blood drop while in flight is usually obvious from the geometry of its resulting bloodstain."— Presentation transcript:
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 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 spines and 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.
TRANSFER BLOODSTAINS: Swipe
Transfer pattern: wipe
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 to 5 feet/sec. Relatively large stains 4mm 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 size 1 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. and greater Preponderant stain size 1mm in size and smaller Mist-like appearance