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The Physics of Blood Spatter

The physics behind blood spatter analysis
by

RebeccA Banning

on 25 April 2013

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Transcript of The Physics of Blood Spatter

The Physics of Blood Spatter RebeccA Banning First of all, what is it? Bloodstain pattern analysis, BPA, falls into the category of forensic science. Analyzing blood stain patterns uses different ideas, taken from biology, mathematics, chemistry and physics. Let's focus on physics for now. Different Blood Stain Patterns There are many different patterns in the way blood lands. There are three distinct blood stain patterns: 1. Passive blood stains: Blood stains that fall only with the force of gravity. An example of this would be a nose bleed. 2. Dynamic Stains: When some force or compression hits the source of blood, causing a splash-like pattern where it lands. 3: Transfer-Contact blood stains: When an object with blood comes into contact with an object without blood. (His foot is the "object with blood", and the rock is the "object without blood" ) The velocity of the object also effects the type of stain created. Low velocity blood spatter: Produced when blood travels less than 1.5 m/s. Medium velocity blood spatter: When blood travels between 1.5m/s and 7.5 m/s (blunt force trauma). High velocity blood spatter: When blood travels more than 30 m/s (gunshot or explosive). Physics in BPA The main focus in BPA related to physics is in the techniques of analyzing the blood. One of these techniques is "Stringing". Stringing is when many strings are attached to blood stains and travelled to the projected area of contact; There are many computer programs today that take the actual strings out of this technique, making it easier to process. String Spatter (Simple computer program ) The Importance of Degrees Different blood stains have different shapes; some simple circles, and others long ovals. These shapes depend on the angle in which blood hits the ground. Let's take a look at the degree of blood in a little more depth. Being able to figure out the angle at which the blood hits the ground is very useful for when you don't have one of these charts to look at. To Sum it All up... Physics is a very important part in blood pattern Analysis, BPA. There are three main types of blood patterns: Passive, dynamic, and transfer-contact blood stains. Physics becomes most important in BPA when Stringing the blood stains. This lets us know where the point of contact was. There are different angles at which blood hits the ground. A formula can be used to find the exact angle. The general basis of the angles are that 90˚ are circles, and drops around 20˚ are long ovals. Overall, physics is just as an important part of BPA as math and biology. Sources: http://www.practicalhomicide.com/Research/LOmar2007-2.htm https://dps.mn.gov/divisions/bca/bca-divisions/forensic-science/Pages/forensic-programs-crime-scene-bpa.aspx http://hemospat.com/ Thank you :)
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