Blood Stain Patterns - Research Paper Example

 Blood Stain Patterns In order to completely understand the interpretation of bloodstains, a person must primarily comprehend the composition of all the properties found in blood.When blood clots are present within bloodstains, they can indicate that the attack on the victim was clearly extended for a long period of time or maybe the victim bled for some significant amount of time after the injury had occurred. Analysis of bloodstain patterns, therefore, refers to the critical examination of the shapes, location and the pattern distribution of blood stains (Jackson 2011).The analysis is significant because it provides an exclusive description of the events that occurred that consequently led to the origin of these patterns. The blood pattern analysis also helps the investigators on confirming the statements made by the witnesses and also gather facts on the most likely perpetrator of the particular crime (James, Kish, & Sutton 2005). A clear understanding of the scientific principles involved with blood must be emphasized.Depending on the injury, when the blood leaves the body it conforms to the general laws of physics.The analyst must be careful when analysis the blood shedding events like this will enable them to understand clearly blood flow.The physical properties of blood when in fluid form, have several properties that resemble water characteristics.Both blood and water are affected by physical forces.The internal friction that is present in most fluids is referred to as viscosity.As fluids flow past each other, the layers that are present among them are responsible for the generation of these frictional forces. Also both cohesion and surface tension forces cause blood drops to maintain their spherical shape once they drop from their point of origin.Cohesion force attracts molecules together while surface tension refers to a force created by the molecules of a fluid when they attain the lowest most stable energy configuration value possible.This value is attained through minimizing the areas that can lead to exposure of the fluid. Impact Spatter usually results from a forceful impact between an object and wet blood.This impact causes the blood to disintegrate into smaller droplets.When the impact is greater, the droplets produced will be much smaller (James, Kish, & Sutton 2005).This is due to a drop in the density of blood that decreases as the movement of the blood drops become further from the blood source.A critical analysis of impact splatter enhances the conclusions on the location of the individual and the objects as the incident being investigated occurred. When an exposed blood source experiences a strong, forceful impact, the surface tension is weakened resulting in the blood being broken up into several minute droplets.The velocity of the force refers to the effect created by the object in regards to the consistency of the speed of the blood droplets.This impact produces These blood droplets.When the droplets collide with a target surface, they produce patterns of blood stains different from the projected and drip patterns.All this aspects of impact are typically associated with force, effect or velocity. However, the point of interest is medium velocity impact blood splatter.This type of blood spatters to stains pf blood produced on a target surface when the source of blood experiences a forceful impact at this velocity, is approximate between 5 and 25 feet per second.Here, the effect is usually linked with stabbings, beatings and fall from this range.Analysts have distinguished, and drawn conclusions with the assistance of the low-velocity category where the force used to the blood are about 5 feet per second. When receiving the impact, the source of blood must be completely exposed to enhance the creation of spatter.Origin, angle of impact, directionality, angle of impact and convergence of the blood stains being analysed, are found by the geometry and location of the stains.The critical analysis of medium velocity blood stain patterns and the origin of the blood stain enables analysts to determine the position of the perpetrator and the victim at the time the incident occurred. Eckert & James (1998, P. 59-61) Cast-off blood stains patterns are caused when the bloodied object is in motion, and the centrifugal force imposed on the mobility of this object leads to blood drops falling on the surface.When the object suddenly decreases its motion as it falls down, this may lead to cessation patterns being formed.If an object is repeatedly moved across the surface of the victim, each preceding swing leads to a cast off as less blood eventually remains on the surface of the object.Cast off blood stains are very hard to interpret as the variables in patterns and assumptions made are numerous in regards to the patterns produced. An object stained with blood when swung through the open air, the forces created by this action causes blood to be flung from the target surface.The blood pattern from this activity is referred to as swung cast off.Cessation cast off occurs when the blood stained object halts abruptly due to its collision with another object at the full extent of the back swing.As long as blood is sufficient for the turned object, and the movement is also enough cessation will occur. However, the blood stain pattern that will be analyzed is the swing cast off blood stain pattern. Fraser & Williams (2013). This pattern occurs when swinging weapon produces blood especially when the force generated by this motion is sufficient to release a blood drop from the accumulated blood to the pool.The collected blood usually is present on the weapon and, therefore, each drop will produce distinguishing variables at the point of origin.The conclusion drawn by analysts is that the staining pattern produced, is likely to be in a series of linear blood spots located on walls and ceilings.This linear pattern is termed as a significant characteristic of a cast off pattern.The information yielded contains details on the area that the weapon was swung during the incident and also the frequency of swings needed to make the scene sufficiently bloody which eventually produces a cast-off. If the blood is insufficient, the linear series is unlikely to be produced. Transfer bloodstains which are also known as contact stains typically occur when contact is present between a bloodied surface and another surface.This contact leads to the transference of blood into the secondary object.Analysing this type of blood stain helps in tracing the events that occurred during the accident as it shows the movements of the individual in regards to the pattern showed.Critical analysis of the blood stain state may significantly help to reveal the duration that has passed since the shedding of blood occurred.After a prolonged period of time, coagulation of blood takes place.Coagulation refers to the action of clotting factors within the blood turning blood into a gelatinous substance from its liquid form.Coagulation highly depends on the blood quantity that is present on the surface.As coagulation occurs, serum stains are formed which happens when the serum that is the liquid part of the blood separates. Instances such as presence of low amounts of blood and also individuals cleaning the blood stains in attempt to hide the occurrence of bloodshed may lead to the naked eye of the analyst not being able to see the blood stains. However, the chemical reagents used to clean the blood stains oftenly leave behind detectable traces of the stain.These traces can be seen by using specific chemicals and light devices.Luminol tests conducted by analysts typically work by mainly reacting with blood constituents and produces a compound referred to as chemiluminescence.However, these chemical reagent tests are not always conclusive as some other substances may react in the same way as blood reacts to them (White 2004). When there is a gap in the continuation of a blood stain, this may lead to assumptions being made that someone may have been in the area caused by the blood stain.This gap is referred to as void.It must be emphasized that the blood found in an incident does not necessarily belong to the victim but, however, could belong to the perpetrator.The perpetrator might have to be injured during the incident. James, Kish, & Sutton (2005 ). When the basis of the direction pursued by the blood stain and the angle of impact have been formed, it becomes easier to establish the point in which the blood stains originated.A critical examination of a particular blood stain may help in determining the direction in which the blood traveled from the point of impact of the target.Satellite stains refer to the small amount of blood that have separated away from the primary or parent stain. The angle of impact refers to the angle in which the droplet of blood hit the intended target.This Angle is typically established by calculating the ratio between the width of the blood stain to its length.When the angle of impact is established, it enhances the probability to determine the point of convergence which refers to an area which multiple travelling stains collide.Eventually, the point of origin can now be been established after these calculations have been done. The evidence collection process usually takes a lot of time as most of the evidence will not be found in the area that the incident occurred. James, Kish, & Sutton (2005).Collection of evidence can only take place after extensive documentation has already been done.The evidence collected must be packaged and stored in an intricate and efficient manner.Efficiency prevents alteration or damage of the blood stains. References A Simplified Guide to Bloodstain Pattern Analysis.Retrieved from: http://www.forensicsciencesimplified.org/blood/principles.html Eckert, G.W., & James, H., S. (1998). Interpretation of Bloodstain Evidence at Crime Scenes , Second Edition Practical Aspects of Criminal and Forensic Investigations.CRC Press. Fraser, J., & Williams, R.(2013). Hand book of Forensic Science.Routledge. Forensic Science.Central Bloodstain Pattern Analysis.Retrieved from: http://forensicsciencecentral.co.uk/bloodstains.shtml Jackson, A. R. W, Jackson, J. M., (2011). Forensic Science. Essex: Pearson Education Limited. James, H., S.,Kish, E.,P. & Sutton, P.(2005).Principles of Bloodstain Pattern Analysis: Theory and Practice.CRC series in practical aspects of criminal and forensic investigations.CRC Press. White, P. C., (2004). Crime Scene to Court: The Essentials of Forensic Science. Cambridge: The Royal Society of Chemistry. Read More