blood spatter

Yesterday at Chicago one of the most intesting things I learned about was blood spatter (not splatter.) Before i didn't know that by just looking at a bit of blood you can find out information like the positions of the victim and perpetrater, direction blood traveled, what weapon was used to cause spatter, the number of blows struck, and direction of travel after injury. Blood droplets can be classified into Passive or Projected spatter. Passive drops look like circles when droped at a 90 degree angle and may be distorted if it doesn't land on something smooth and hard. If it drops at an angle it makes a shape that looks like an elipse with a tail pointing toward the direction the blood was traveling. The angle can be found by taking the width of it divided by the length to get the sine of the angle the blood was spattered at. Doing this with multiple drops can tell us the source of the spatter. If the spatter looks like it was from a mist of blood it traveled at a high velocity, but if it is more condensed with larger droplets, it was only medium.