accurately measuring blood drops
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/1.jpg)
Accurately Measuring Blood Drops
How to accurately measure blood spatter in order to find angle of
impact (AOI) and point of origin.
![Page 2: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/2.jpg)
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!!!!!
![Page 3: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/3.jpg)
How to read Vernier Caliper
• Add pix
![Page 4: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/4.jpg)
You Tube can help!!
• Video showing how to read a caliper (inches)– http://www.youtube.com/watch?v=Vz40xmrdhyY
![Page 5: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/5.jpg)
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.
![Page 6: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/6.jpg)
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.
![Page 7: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/7.jpg)
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)
![Page 8: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/8.jpg)
Angle of Impact
length
width
Angle of impact = arc sin W/L
Distance from point of convergence
Hei
ght a
bove
poi
nt o
f co
nver
genc
e
Origin
85 60 45 30
![Page 9: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/9.jpg)
Angle of
Impact
90
10
70
2030
60 50 40
80
W
a
l
l
Floor
Path of blood
![Page 10: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/10.jpg)
Determine Angle of ImpactWidth Length sine arc sine
2 3 .6667 42°
1 4 .25
9.6 9.7
14.5°
.9897 82.2°
Hand-out
![Page 11: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/11.jpg)
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
![Page 12: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/12.jpg)
LENGTH = 5.9cm
WIDTH = 2.6cm
Finding AOI
![Page 13: Accurately Measuring Blood Drops](https://reader036.vdocuments.us/reader036/viewer/2022062323/56815a62550346895dc79e54/html5/thumbnails/13.jpg)
SOLUTION:
AOI = SIN-1 W / L
AOI = SIN-1 2.6/5.9
AOI = SIN-1 (.44)
AOI = 26.2°