Blood Spatter Analysis Blood Spatter Analysis ng di

“Blood Spatter Analysis”

Blood Spatter Analysis ng di n a st Out + I can extrapolate a trend on a graph to predict a spatter size + I can construct a data set which can be plotted on excel to find a trend line +I can conduct my own experiment to investigate a blood spatter dimension such as diameter. I can identify some possible blood spatterns from a crime scene Mr D Powell 2019

Three main types of spatter…. https: //www. youtube. com/watch? v=zjfdpenl 1 Rc Mr D Powell 2019

Pattern Types – Game…. Types…. 1 2 3 4 5 6 7 8 9 10 11 12 1. Swipe pattern 2. Low velocity impact (LVIS) 3. Void 4. Expirated Blood 5. Transfer. Contact Pattern 6. Saturation 7. Medium Velocity Impact Spatter (MVIS) 8. Passive Drop 9. High Velocity Impact Spatter (HVIS) 10. Pool 11. Arterial Spurting Pattern 12. Wipe Pattern Mr D Powell 2019

Are you qualified? Types…. 5 4 1. 2. 3. 4. 5. 6. 7. Swipe pattern Low velocity impact (LVIS) Void Expirated Blood Transfer-Contact Pattern Saturation Medium Velocity Impact Spatter (MVIS) 8. Passive Drop 9. High Velocity Impact Spatter (HVIS) 10. Pool 11. Arterial Spurting Pattern 12. Wipe Pattern 8 11 1 7 4/7 Mr D Powell 2019

Introduction…. Many patterns that appear at crime scenes are useful for reconstruction. In some of the cases, these patterns can be “collected” only by documentation; that is, they cannot be “packaged” and taken back to the crime lab. If these patterns are interpreted properly, they can provide information about the events and can often times be more reliable than witnesses. Blood spatter is probably the most common type of reconstruction pattern. Blood spattern interpretation is something of a subspecialty in forensic science. Mr D Powell 2019

Physics of the Droplets? Droplets of blood falling or projected through space follow standard physical laws. Those laws provide the scientific basis for understanding blood patterns. By virtue of its makeup, viscosity, density, and other physical properties, blood forms predictable patterns when it falls or is projected through the air and impacts a surface. Investigators sometimes use the state of the partially dried blood to draw inferences about how much time has elapsed since the blood was shed. Blood drying time will also be influenced by heat, humidity, air circulation, and the target surface. It should also notice that there are so many factors in blood analysis that sometimes two possibilities exist and there not one definitive answer. Mr D Powell 2019

Impact Velocities? Blood spatter is often classified as low, medium, or high velocity. A low-velocity blood spattern is any pattern formed where gravity is the only force acting on the blood. (1 m/s) A medium-velocity blood spattern is formed when moderate force from some object causes pooled blood to “scatter” in all directions. The force causes the droplets produced to be smaller so the resulting pattern consists of more and smaller droplets than are seen in typical lowvelocity patterns. These patterns are typically produced by an external force such as the use of blunt force or someone stomping his foot or shoe into pooled blood. It could also be produced by an arterial spurt. (5 m/s) A high-velocity blood spattern is the result of extreme force acting on a blood source. As a rule, such patterns are seen only in connection with gun shots, explosions, or the high impact forces of a vehicle crash. (30 m/s) Mr D Powell 2019

Impact Angles? The shape of a blood spatter droplet indicates the angle from which it impacted the surface. A blood droplet hitting a non absorbent surface at a 90 -degree angle (perpendicular to the surface) results in a circular stain. As the angle changes, the resulting stain becomes more elliptical. In fact, using measurements and some elementary trigonometry can estimate the angle of incidence of a blood stain. Mr D Powell 2019

What can Blood Spatter Analysis find out? • • Time of Death Nature of Injuries Left of Right handed assailant Gun and Ammunition type Mr D Powell 2019

Theory of spatter size! As the blood falls through the air, it takes the shape of an oscillating sphere. The blood droplets will not break up in the air as they fall due to gravitational force alone. The diameter of the bloodstain is dependent upon the distance the drop falls to the horizontal surface as well as the volume of the blood drop. (a control variable in our experiment) As the distance of the fall increases, the diameter of the bloodstain will increase until it reaches a maximum diameter. The maximum diameter for the bloodstain occurs after the drop has fallen approximately 1. 8 m Mr D Powell 2019

Blood Spatter Analysis Sheet – Short Version (Y 8) 50 mm = 100 mm = 150 mm = 200 mm = 250 mm = 300 mm = 350 mm = 400 mm = 700 mm = Use the sheet to measure the diameter of each spatter in mm, don’t measure the 1. 5 m one yet we will predict it in excel 450 mm = 500 mm = Mr D Powell 2019

Blood Spatter Analysis Sheet – Tall Messy Version 100 mm = 200 mm = 300 mm = 400 mm = 500 mm = 600 mm = 700 mm = 800 mm = 1500 mm = Use the sheet to measure the diameter of each spatter in mm, don’t measure the 1. 5 m one yet we will predict it in excel 900 mm = 1000 mm = Mr D Powell 2019

Secondary Research Data…. . This topic is widely researched and here are two examples of data. The top one is a really good example but they need to do a line of best fit. . Mr D Powell 2019

Possible Relationships? What did you find and extrapolate? Graph to Show the Blood Spatter Size v Drop Height 22. 0 20. 0 18. 0 Spatter Diamter /mm Graph to Show the Blood Spatter Size v Drop Height 16. 0 14. 0 R 2 = 0. 968 12. 0 16. 0 14. 0 12. 0 R 2 = 0. 9091 10. 0 0 500 1000 Drop Height /mm 1500 0 500 1000 Drop Height /mm Mr D Powell 2019 1500

Extra Reading… Falling droplets from a bleeding source that is stationary will generally result in blood pooling below the source. It may be possible to discern separate “droplet” patterns in the pool. If a dripping blood source is moving fast enough, the droplets may show which direction the source was moving Contact deposit patterns result from an object coming into direct contact with a blood pool or blood source. These patterns can appear on clothing or on objects at scenes. Sometimes it is important to determine what object caused the pattern. Wipe and swipe patterns result when an object contacts or transfers wet blood and smears on a surface. A wipe pattern is created by an object contacting an existing bloody surface with motion. A swipe pattern is created by a bloody object contacting another surface with motion. Running patterns are just what the name says. Blood hits a vertical surface but the volume is sufficiently high that gravity causes the droplet to run down. An arterial spurt pattern results when an artery is cut or severed and blood is literally pumped out of the body by the beating hear and onto a nearby surface. These patterns generally contain quite a bit of blood. In addition, an individual with a seriously severed artery is losing blood at such a rate that he or she will not be able to move too far and without immediate and extreme medical intervention will die fairly quickly Cast-off patterns result when a bloody object is swung and throws off droplets onto a nearby surface. These patterns may be seen on ceilings or walls and occasionally on floors. Secondary spatterns result when blood drops fall into a preexisting pool of blood. As each drop hits the liquid surface, it can cause small droplets to splash upward and some of these may hit a nearby vertical surface. Mr D Powell 2019

Practical Order Class set to enable paired practical, each set… 1. Clamp 2. Stand 3. 2 x 1 m ruler 4. Boss 5. A 3 Worksheet for spatter 6. Set Square 7. Blutac 2 blobs 8. Laptop with Excel 9. Blood Sample (preferable fresh human!) in beaker or vial 10. Small disposable Pipette 11. Cloths for clean up 12. Eye protection 13. Newspaper (under the paper) Mr D Powell 2019