Bloodstain patterns Essay Example

  • Category:
    Biology
  • Document type:
    Essay
  • Level:
    Masters
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Bloodstain Patterns

Bloodstain patterns

Introduction

In bloodstain pattern analysis, we focus on the stain’s physical characteristics. The shape, size, distribution, surface texture, location and the overall appearance of the stain gives different types of patterns of bloodstains. Bloodstain patterns help in determination of the cause of the bleeding (Peschel, Kunz, Rothschild & Mützel 2011). Analysts use bloodstain patterns to develop explanations on the type of crime that has caused the bleeding, the person from whom the blood has come from and whether the bleeding has been influenced by other factors.

Bloodstain pattern depends on the propelling force, quantity of the blood and the nature of the surface where the stain lands on. For instance, bloodstains from gunshot wounds should form smaller blood droplets and should spread on a relatively wide area while blood from an impact spatter is expected to form larger blood droplets which appear to be dominated in the region around the action (Vernon, 2006). When a blood’s drop is dropped vertically on a particular surface, the drop forms almost a spherical shape. This means that, bloodstain patterns also depend on surface tension force and cohesive forces. This spherically shaped blood drop will distort slightly if it lands on a relatively smooth surface but if it lands on rough surfaces, it breaks apart since its surface tension is interrupted (Peschel, Kunz, Rothschild and Mützel 2011).

Differentiating airborne stains from contact stains

Blood staining on individuals or items is deposited in only two ways: airborne and contact deposition (Vernon, 2006). Contact blood staining is the one that arises when two surfaces come into contact and one surface contains some wet blood. In some cases, the blood satin can be used to determine the object which imposed the mark on the surface. When an object is wet with some blood and then it is involved in a moving contact with another object, contact stains which are smeared are mapped on the object which initially had no bloodstains. When wet blood becomes airborne as a result of application of some force, it results to airborne bloodstains (James 2005). With airborne bloodstains, the direction in which the blood was travelling can be determined after the blood pattern is analyzed which helps in examination of the stain’s shape. Examples of airborne bloodstains include: impact spatter resulting from cases associated with assault, passive drips often seen when blood flows from a particular source with wet blood under gravity, cast off and ex-pirated blood (James 2005).

Differentiating a wipe from a swipe

A swipe results when blood is transferred from a surface bearing a wet blood onto a blood non-bearing surface. A swipe bloodstain shows some features of relative motion which happened between the surfaces. A wipe results when an object moves through a wet bloodstain which already preexisted (Gardner 2004). A wipe results to impact patterns since objects strike a liquid blood. A swipe leads to spatter stains since blood drops are dispersed in the air as a result of application of external force on the liquid blood.

A wipe also leads a transfer stain since a contact is established between two surfaces with one surface bearing a blood. Spatter patterns of bloodstains that result from swipe can be differentiated from the other patterns since they occur inform of broken up droplets of blood masses (Gardner 2004). The droplets are usually projected to the scene’s surrounding surfaces from their origin due to the forces brought about by the motion between the moving surfaces. Spatter patterns are influenced by the surfaces where they strike. This results to different blood drops’ appearances and sizes.

The size of the drops and their appearance also depends on the manner in which the blood is deposited or projected. Projected bloodstains occur when a blood source which is exposed is acted upon by force which is greater than gravitational force. The number, shape and size of the blood drops depend on the total amount of utilized force while striking the source of the blood. A swipe also results to cast-off bloodstains (Gardner 2004).

The bloodstains occur when motional bloody objects throw or project blood onto another surface. Usually, beating events are associated with cast-off patterns (Bevel & Gardner 2002). Cast-off bloodstains depend largely on the size of the pattern but in some cases, they are affected by the weapon’s size, the blow’s force and the bloody injuries’ extend. A wipe leads to pattern transfer. Pattern transfer caused by wipe occurs when objects containing wet blood are in contact with others whose surfaces are not bearing bloodstains.

Differentiating impact spatter from aerated blood

Impact spatter is a category of a blood spatter and occurs when a source of liquid blood is subjected to force. Impact spatter depends on the blood’s speed as it leaves your body and also depends on the kind of force the source of blood is subjected (Vernon 2006). Examples of impact spatter include: gunshot spatter, cast-off, arterial spray and ex-pirated spatter. Gunshot spatter include backward spatter from wound’s entrance and the exit wound’s forward spatter. Gunshot sputter depends on the kind of gun used, where the person is struck, final position of the bullet, victim’s position in relation to walls, objects and floors and the victim’s distance from the gun. Typically, mist from forward spatter is fine while the one from back spatter is larger (Vernon 2006).

Cast-off occurs when blood is flung on objects’ surfaces by swinging objects following an arc. This usually occurs when bloodstained objects are swung back by assailants before they have inflicted another blow. Impacting object’s direction can be determined by analysts by considering the patterns shape as the motion’s direction is pointed by the drops’ tails (Vernon 2006).

The number of arcs can be used to tell the delivered blows’ minimum number. Arterial spray occurs when blood is released as a result of major artery severity (Adam 2008). This usually occurs when blood vessels bleached within the body allow blood to be propelled out due to the pumping action of the heart. The blood forms large arcing patterns with large stains. Ex-pirated spatter occurs when blood from internal injuries mix with the air expelled from lungs through nose or mouth (Adam 2008). Ex-pirated spatter leads to formation of fine mist as a result of the force produced by lungs in their effort to move air from the body. This kind of spatter typically consists of small bubbles of air in the blood drops.

Conclusion

Analysis of bloodstain pattern is one of the disciplines that require formal training incorporated with a couple of years of experience since determination of coverage areas and origin and employment of trigonometric methodologies or string methods calls for specialists who are trained due to their complexity(Geberth 2007). Bloodstain patterns depend on the size, shape, location and distribution of the stains of the blood in the respective scene. Bloodstain patterns are essential in investigating the causes of different crimes that lead to loss of blood.

References

Adam, C.A. (2008). Bloodstain Pattern Analysis. Forensic Evidence in Court: Evaluation and Scientific Opinion, pp.277-292.

Bevel, B.T. & Gardner, R.G. (2002). Bloodstain Pattern Analysis with an Introduction to Crime Scene Reconstruction, 2nd Edition, Boca Raton, Florida: CRC press

Gardner, R.M. (2004). Practical Crime Scene Processing and Investigation, Boca Raton, Florida: CRC press

Geberth, V.G. (2007). Bloodstain pattern analysis. Law and order-Wilmette then deer field-, 55(3), p.38.

James, S.J. (2005). Principles of Bloodstain Pattern Analysis Theory and Practice, Boca Raton, Florida: CRC Press

Peschel, O.P., Kunz, S.N., Rothschild, M.A. and Mützel, E.M., (2011). Blood stain pattern analysis. Forensic science, medicine, and pathology, 7(3), pp.257-270.

Vernon, J.G. (2006). Practical Homicide Investigation: Tactics, procedures and Forensic Techniques, Forth Edition. Florida: CRC Press