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Blood Spatter Analysis. Bloodstain Pattern Analysis (BPA). While the use of bloodstains as evidence is not new, the application of modern science has brought it to a higher level.
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Bloodstain Pattern Analysis (BPA) • While the use of bloodstains as evidence is not new, the application of modern science has brought it to a higher level. • New technologies (DNA analysis) are available for detectives and criminologists to use in solving crimes and apprehending offenders.
Bloodstain Pattern Analysis (BPA) • BPA applies scientific knowledge from other fields to solve practical problems • Draws from biology, chemistry, math and physics • Produces strong, solid evidence
BPA can determine • Location and description of individual stains and patterns • Mechanism that created the stains • Direction a blood droplet was traveling • Area of origin • Type of object used in attack • Minimum number of blows • Presence of a subject at a scene • Positioning of the victim, suspect and objects during events • Sequence of events
Determining angles of impact • Blood droplets in freefall have the shape of a sphere. • Droplets striking surfaces and leaving well-formed stains make it possible to determine the angle at which the droplet struck the surface.
Determining angles of impact • A well-formed stain is in the shape of an ellipse • L/W followed by taking the inverse sin (sin-1) gives the impact angle
Point and area of convergence • The point of convergence is the intersection of two different bloodstain paths
Point and area of convergence • The area of convergence is the box formed by the intersection of several stains from opposite sides of the impact pattern
Point and area of Origin • Point (Area) of Origin – the common point (area) in three dimensional space to which the trajectories of several blood drops can be retraced
Target surface texture • Bloodstains can occur on a variety of surfaces, such as carpet, wood, tile, wallpaper, clothing….. • 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.
Target surface texture • Blood droplets that strike linoleum flooring take on a slightly different appearance. • Notice scalloping around the edge of the blood droplets.
Target surface texture • Surfaces such as wood or concrete are distorted to a larger extent. • Notice the spines and secondary spatter present.
Bloodstain pattern categories • Classifies stains based on the mechanism that created them. • Passive bloodstains - created when gravity is the force acting upon it. • Projected bloodstains- occur when some form of energy has been transferred to a blood source • Transfer or contact- produced when an object with blood on it comes in contact with an object or surface that does not have blood on it.
Passive Drop A bloodstain drop(s) created or formed by the force of gravity acting alone
Drip Pattern A bloodstain pattern that results from blood dripping into blood
Flow Pattern A change in the shape and direction of a bloodstain due to the influence of gravity or movement of the object
Low Velocity Impact (LVI) Relatively large stains 4 mm in size and greater. Impact velocity up to 5 feet/sec
Medium Velocity Impact (MVI) Preponderant stain size 1 to 4 mm size. Impact velocity of 5 to 25 feet/sec.
High Velocity Impact (HVI) Preponderant stain size 1 mm in size and smaller. Mist like appearance. Impact velocity of 100 feet/sec and greater.
Cast-off Pattern A bloodstain pattern created when blood is released or thrown from a blood-bearing object in motion
Arterial Spurting or Gushing Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery
Back spatter – blood directed back towards the source of energy or force that caused the spatter • Expiratory blood – blood that is blown out of the nose, mouth or a wound as a result of air pressure and/or air flow which is the propelling force
Swipe Pattern The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.
Hair swipe Pattern The transfer of blood from a moving source onto an unstained surface. Direction of travel may be determined by the feathered edge.
Wipe Pattern A bloodstain pattern created when an object moves through an existing stain, removing and/or altering its appearance.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Transfer Pattern A recognizable image of all or a portion of the original surface may be observed in the pattern.
Sources • BPA Tutorial http://www.bloodspatter.com/BPATutorial.htm • Blood Pattern Analysis (Wikipedia, I kid you not!) http://en.wikipedia.org/wiki/Blood_pattern_analysis_at_crime_scenes • International Association of B. P. Analysts http://www.iabpa.org/