Human bodies are leaky. If pierce to any depth they tend to gush or spray blood aimlessly. Show
This is hardly surprising since the average-sized adult male has between five and six quarts of blood gurgling through their system (females and children have slightly less). It can gush, it can drip, or spatter across the air forming a pattern from a wound. Crimes involving violent contact between individuals are frequently accompanied by bleeding and resultant bloodstain patterns. Crime-scene analysts have appreciated the analysis of bloodstain patterns that were deposited on floors, walls, ceilings, bedding, and other relevant objects for providing valuable insights into the events that might occur during the commission of a crime.
Surface Texture And Bloodstain PatternsSurface texture is of paramount importance in the interpretation of bloodstain patterns; comparisons between standards and unknowns are valid only when identical surfaces are used.
Note 1: Satellite spatter are small drops of blood that are distributed around the perimeter of a drop or drops of blood and were produced as a result of the blood impacting the target surface. Directionality of Angle of ImpactThe direction of blood striking an object is determined using the pattern it makes. The distorted or disrupted edge of an elongated stain indicates the direction of travel of the blood drop. In general, satellite spatter around parent stains will have the pointed end facing against the direction of travel. As the stain becomes more elliptical in shape, its direction becomes more detectable because the pointed end of a bloodstain faces its direction of travel. Angle of Impact of Bloodstain PatternsThe impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion. The formula is given by, Sin A= (Width of bloodstain)/ Length of bloodstain Footnotes:
For example, the width of a stain is 1.75cm and length is 3cm,
Dropping DistanceIn general, bloodstain diameter increases as height increases. Also Read: Impact Bloodstain Spatter PatternSpattered blood is defined as a random distribution of bloodstain that varies in size that may be produced by a variety of mechanisms.
Moreover, as the force of impact on the source blood increases, the velocity of blood droplets leaving the source of blood also increases. And the resultant blood drops size decreases. On the basis of the velocity of the force impacting on a bloody object spatter is classified as follows: 1. Low-Velocity Spatter These are large separate or compounded drops caused by an impact of fewer than five feet per second; blood cast off from fist, shoe, weapon, dripping, or splashing. This kind of spatter is normally produced by gravity alone, by a minimal force. The resulting blood spots are mostly 4 to 8 mm in diameter. 2. Medium-Velocity Spatter Caused by an impact of 5 to 25 feet per second; blows with a baseball bat, hammer, axe, or similar instrument. These are small drops with diameters of 1 to 4 millimeters. 3. High-Velocity Spatter Caused by an impact of 100 feet per second; almost always gunshot, but occasionally produced by contact with high-velocity machinery. The smallest of all, these blood spots are typically less than 1 mm in diameter, producing a fine mist-like spray, much like an aerosol. Origin and Analysis of Impact Bloodstain PatternsA. Area of ConvergenceArea of convergence is obtained by:
Note 2: An object hitting a source of blood numerous times will never produce exactly the same pattern each time. B. Area of OriginTo depict the area of origin,
Types of Bloodstain SpatterA. Gunshot Spatter
B. Cast-off Spatter
Example: Three casts off are found at a crime scene, the first blow will produce no cast off; swing back will produce the first cast off then the second blow will produce the second cast off then swing back will produce the third cast off.
C. Arterial Spray Spatter
D. Expirated blood Pattern
E. Void Patterns
Types of Bloodstain PatternsNot all bloodstains at a crime scene appear as spatter patterns. The circumstances of the crime often create other types of stains that can be useful to investigators.
For example: If we find some blood-laden footprint on the crime scene, the first print produced will always be heavy or dark with blood; followed by some lighter prints. These prints will also indicate whether the person was walking or running as the running footprints have a large space gap between them B. Flow Pattern
C. Swipe and Wipe Pattern
Note 3: the object with blood should be moving to form this pattern or else it will be known as a transfer pattern.
D. Drip Patterns
E. Pools
Note 4: Skeletonization: The process by which the edges of a stain dry to the surface in a specific period of time (dependent on environmental and surface conditions); skeletonization remains apparent even after the rest of the bloodstain has been disturbed from its original position. This may be important for classifying the source of the original stain. References:
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