Crime scene is the location of a crime where forensic evidence is being collected. It could be the site of a murder, an accident or a fire.
Forensic science pioneer Edmond Locard once observed that it is impossible for criminals to go anywhere in the world without leaving traces behind them. These traces are called ‘evidence’ and they serve as silent witnesses against the offender. When the police come to investigate a crime, they will visit the crime scene and take note of everything they see there. This is what is known as a crime scene sketch. It’s a visual depiction of all the things that are found in a room, such as the layout, items and even the direction the light is coming from.
Once a crime scene has been photographed, it’s then locked down and the people who were there during the offence must leave the area. This is to avoid contamination as any contaminants can contaminate the evidence or even mislead it. This is known as contamination control and it is very important in crime scene investigations.
Once the crime scene has been secured, police will decide which pathway they will use to re-enter the room and conduct their investigations. Typically they’ll choose a point of entry and exit and stick with it for the duration of the investigation, to ensure that they don’t miss any evidence. They’ll then perform a thorough search of the crime scene, usually using one square metre at a time.