By: Neil Harrison ~
The key principle in Crime Scene investigation is the concept known as 'Locard's Exchange Principle'.
It states that whenever someone is present at the scene of a crime, something physical is either left behind and/or taken away.
This principle allows investigators to link suspects, victims and scenes/objects through 3 primary methods;
1. Associative Evidence - trace evidence directly linking a suspect to the scene/location of the crime
2. Reconstructive Evidence - helps determine the actions and events that took place at the scene/location
3. Control Evidence - scene samples used to circumstantially link a suspect to a scene usually at a later date
It is important to note that evidence that may be collected in order to identify and prosecute a suspect, is equally important in excluding potential suspects during an effective investigation.