They can be used to convict the guilty. The patterns of the spatters and the shapes of the individual blood droplets themselves can tell how the crime was committed. A drop falling from a low height of a few inches will leave a small cohesive circle. At greater heights, the circle will be larger and may even have a 'crown' effect. Hitting a surface at an angle does even more to disrupt a blood droplet.
Perpendicular impact leaves a droplet fairly uniform, as shown below.
A droplet hitting a surface at an angle will bulge out in one direction, indicating the direction of travel of the droplet. Pulling back from a blow produces a blood spatter that indicates direction, by creating an arc of blood droplets. You can determine the number of blows inflicted by counting the arcs. You can also determine the orientation of the individuals involved, the size of the object used and the right or left handedness of the assailant. Click here to go to the next page.