Blood Spatter Analysis

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What influence does the height at which simulated blood is dropped have on the size of the blood spatter?

Police use many different scientific techniques to solve crimes such a murder cases. They dust for fingerprints, use special lights to look for blood, use chemicals to find out what mysterious substances are, and sample DNA. And in addition to figuring out who did it, they have to figure out how he did it. And to do that, they often use a technique called blood spatter analysis. Blood is primarily made of water and as such, it behaves much like water and therefore must obey the laws of motion and gravity. Particles in the blood are attracted to each other and this cohesive property causes blood that falls onto a surface to leave behind
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If a lot of blood was lost, the blood droplets will be quite large. Detectives use this information when determining whether a person died or not.

The shape of the blood stain depends on the angle of the blood when it hit the surface and the speed at which the blood drop was travelling. A droplet that has fallen vertically will be more round than a droplet that has hit the surface at an angle which will be oblong shaped.

Drops that hit at an angle form a tail which typically points in the direction that the drop
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The spatters were given time to dry. 8. The diameter of each spatter was measured in mm.

9. The results were recorded.

10. Steps 2–9 were repeated for heights 20cm, 60cm and 100cm.

The straw was not the best apparatus to use as it would sometimes let off more than one drop which adjusted my results at a height of 60cm. I noticed that the higher the simulated blood was dropped on, the more ellipses would form. I also noticed, the greater the amount of blood dropped, the larger the diameter of the circle. The splatters dried from the outside, inwards, just like real blood. The simulated blood has similar properties to water, such as capillarity.

Tables showing the relationship between the height at which simulated blood is dropped and the size of its diameter if it is dropped at a height of 20cm

Size of Diameter
Test 1
Test 2
Test 3

Tables showing the relationship between the height at which simulated blood is dropped and the size of its diameter if it is dropped at a height of 60cm Size of Diameter
Test 1
Test 2
Test 3

Tables showing the relationship between the height at which simulated blood is dropped and the size of its diameter if it is dropped at a height of 100cm Size of Diameter
Test 1
Test 2
Test

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