Blood analysis
Friday 9/20
Learning target: I can calculate the point of origin of a
blood stain
Bellringer: Who is Sam Shepherd?
Monday 9/23
Learning target: I can calculate the point of origin of a
blood stain
Bellringer: What is the angle of impact for a drop of
blood that is 5mm wide and 10mm long?
Remember law of sin’s (signs)
**grades, and lab clothing
Blood
Passive blood stains (PBS)
Falls at a 90°angle
No force besides gravity
Circular drop
Projected blood spatter
Falls at a smaller angle than 90°angle
Gravity and another force contribute to the velocity
Elongated drop
High velocity and low velocity
Terms
Point of convergence
Angle of impact
Slant at which blood strikes the surface
Point of origin – the height at which the blood
originates
Angle of impact
Find the width and length of the blood drop
2. Divide the width by the length
3. Take the inverse sin of number 2 to find the angle
1.
Example
Width of the drop = 5mm
Length of the drop = 12mm
What is the angle of impact
Example
Width of the drop = 10mm
Length of the drop = 22mm
What is the angle of impact
Point of origin
1. Find the angle of impact
2. Find the length of the drop of blood to the point of
convergence (the adjacent side)
3. Convert the length of the drop in mm to feet
4. Take the tangent of the angle and multiply it times the
length of the adjacent side in feet
5. You now know the height of the wound!
Example one
1. angle of impact
Width of the drop = 6 mm
Length of the drop = 18mm
2. The length of the adjacent side is 3mm
3. 1mm=.3feet
4. Take the tangent of the angle and multiply it times the
length of the adjacent side in feet
Try it on the worksheet!!!
Example 2
1. angle of impact
Width of the drop = 5mm
Length of the drop = 12mm
2. The length of the adjacent side is 3mm
3. 1mm=.3feet
4. Take the tangent of the angle and multiply it times the
length of the adjacent side in feet
Try it on the worksheet!!!