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Accurately Measuring Blood Drops

Accurately Measuring Blood Drops. How to accurately measure blood spatter in order to find angle of impact (AOI) and point of origin. Accurate Measurement. Vernier Caliper Instrument used to measure with a high degree of accuracy Accuracy is very important for a murder case

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Accurately Measuring Blood Drops

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  1. Accurately Measuring Blood Drops How to accurately measure blood spatter in order to find angle of impact (AOI) and point of origin.

  2. Accurate Measurement • Vernier Caliper • Instrument used to measure with a high degree of accuracy • Accuracy is very important for a murder case • Measuring blood drops requires high degree of accuracy • YOU wouldn’t want to be responsible for letting a murderer go free!!!!!

  3. How to read Vernier Caliper • Add pix

  4. You Tube can help!! • Video showing how to read a caliper (inches) • http://www.youtube.com/watch?v=Vz40xmrdhyY

  5. Caliper Practice • Accurately measure to width of a meter stick at your station. • Accurately measure the width of a pencil at your station. • Accurately measure the diameter of a marble at your station. • Accurately measure the inner diameter of the roll of tape at your station.

  6. Caliper Practice Answers • Accurately measure to width of a meter stick at your station. • Accurately measure the width of a pencil at your station. • Accurately measure the diameter of a marble at your station. • Accurately measure the inner diameter of the roll of tape at your station.

  7. Measure Very Accurately • Use Vernier Caliper • Measure Width • Measure Length (round off ellipse) • As shown in diagram • Calculate Width/Length • Calculate sin-1 of the W/L (same as arc sin)

  8. Origin Height above point of convergence 85 60 45 30 Distance from point of convergence length Angle of Impact width Angle of impact = arc sin W/L

  9. 80 90 10 60 50 40 70 20 30 Angle of Impact Path of blood W a l l Floor

  10. Determine Angle of Impact Width Length sine arc sine 2 3 .6667 42° 1 4 .25 9.6 9.7 14.5° .9897 82.2° Hand-out

  11. By accurately measuring the length and width of a bloodstain, the impact angle can be calculated using the SIN formula below: AOI = SIN-1 W / L

  12. EXAMPLE Finding AOI LENGTH = 5.9cm WIDTH = 2.6cm

  13. SOLUTION: AOI = SIN-1 W / L AOI = SIN-1 2.6/5.9 AOI = SIN-1 (.44) AOI = 26.2°

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