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
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4. You Tube can help!! Video showing how to read a caliper (inches)

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. 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

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

10. Determine Angle of Impact
Width Length sine arc sine °
14.5° °
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)