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What does blood drops tell us?

Figure 2.1

The usual scenario at crime scenes involve  technicians dusting for fingerprints and collecting trace evidence like fibers and hair. The most telling of all is the blood spatters all over the place as seen in figure 2.1. What do these spatters tell? Will it be able to give clues as to who committed the crime, when it happened, and where the assault took place in the room? Does it suggest what kind of weapon was used on the victim and how far the assailant was from the victim? Blood spatters tell tales so this requires a closer look at the blood spatters just as the investigator is doing in figure 2.2.


Hypnotized splatter by girl enchanted

Figure 2.2

To be able to answer the above questions, one must know  how are spatters formed?

The direction of blood droplets can be determined from the shape that it forms when they hit the flat surface. The tail of the elongated drop points to the travel direction.

This droplet was traveling from bottom left to upper right. the victim may be somewhere in the lower left. blood droplet that looks like this may have been caused by a blunt object and is called a projected bloodstain. On the other hand blood stain that falls directly to the ground as seen in self-inflicted wound, accidental wounds and stabbings is called a passive blood stain.

The shape of blood spot formed depends on the height of the blood source as shown in figure 2.3. The higher the height the bigger is the radius of the blood spot.


  Figure 2.3

Blood spatters may reveal:

  • Origin of blood stain
  • Distance of blood stain from target
  • Direction from which blood impacted
  • Speed by which blood left its source
  • Position of victim and assailant
  • Movement of victim and assailant
  • Numbers of blows, shots and etc.
Blood spot shape also changes as the direction of the blood to the impacted surface changes. As the angle of impact becomes more acute the angle becomes more elongated.

Figure 2.4