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 Measuring blood drops requires high degree of accuracy YOU wouldn’t want to be responsible for letting a murderer go free!!!!!

How to read Vernier Caliper Add pix

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

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.

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.

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)

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

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

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

EXAMPLE Finding AOI LENGTH = 5.9cm WIDTH = 2.6cm

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