Potential & Kinetic Energy:
It is important to calculate the amount of energy needed to cause specific wounds on a body. This requires an understanding of potential and kinetic energies, having to do with the laws of thermodynamics. Potential energy has to do with the position of one object to another. Suppose you pull a rubber band back in order to strike your sister on the arm. You have created the possibility of energy once you let go of the rubber band. Kinetic energy is proportional to the velocity and mass of an object when it impacts on another. The energy is measured in Joules. This happens when the rubber band is let go and it impacts from a certain distance on your sister’s arm. Scientifically, the sound you hear from your sister is the result of her pain and frustration with you :)
It doesn’t happen often, but sometimes death scenes are staged. This occurs when the perpetrator wants you to believe a certain thing happened at the scene. They rearrange the evidence to lead suspicion away from themselves or even try to change the actual manner in which the person died. It could be hanging a person after they have been killed to make it look like a suicide or fake an illegal entry into a home to make one believe that an intruder caused the death, rather than someone from inside the home. The key to not being deceived by a staged scene is good scene documentation. The most valuable tool in documentation is photography. Overall, medium range and close up photographs preserve a scene in time. Even years later clues to staging can be found from the good work of the original CSI team. Detecting staging is the process of studying patterns. Many times those that stage try too hard and the look of randomizing events give way to overt patterns that one can tell are trying to lead the investigators to one conclusion. Staging a scene indicates a certain amount of premeditation and planning. This is important in building the profile of the suspect.
Just like the name implies, marks made by weapons or tools can tell us a lot. One example is a patterned wound on a body. A convex tool or weapon, like a tire iron or round rod will many times leave two parallel red lines on the body. This is because when the tool hits the body, the blood in the skin is pushed out to the side of the tool at impact. The center of the impact is blanched due to the loss of the blood in the area of impact. Tool marks on doors, furniture and other objects can lead to a particular classification of tool or may under a comparative microscope individualize the exact tool used by wear marks.